Genetics

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Genetics
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Genetics
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Experimental genetics began in an abbey garden

• The modern science of genetics began in the 1860s
  when a monk named Gregor Mandel deduced the
  fundamental principles of genetics by breeding
  garden peas.
• Mendel lived and worked in an abbey in Austria.
• Strongly influenced by his study of physics,
  mathematics, and chemistry at the University of
  Vienna, his research was both experimentally and
  mathematically rigorous, and these qualities were
  largely responsible for his success.

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Mendel

• In a paper published in 1866, Mendel correctly
  argued that parents pass on to their offspring
  discrete hereditary factors.
• He stressed that these hereditary factors (today
  called genes) retained their individuality
  generation after generation.
• In other words genes are like marbles of
  different colors just as marbles retain their
  colors permanently and do not blend, no matter
  how they are mixed, genes permanently retain
  their identities.

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Mendel

• Mendel probably chose to study garden peas
  because he was familiar with them from his rural
  upbringing, they were easy to grow, and they came
  in many readily distinguishable varieties.
• Perhaps most importantly, Mendel was able to
  exercise strict control over pea plant matings.

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Mendel

• The petals of the pea flower almost completely
  enclose the reproductive organs.
• Consequently, pea plants usually self-fertilize
  in nature. That is, pollen grains land on the
  egg of the same flower.

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Mendel

• Mendel could ensure self-fertilization by
  covering a flower with a small bag so that no
  pollen from another plant could reach the egg.
• When he wanted cross-fertilization (fertilization
  of one plant by pollen from a different plant),
  he used a particular method so that he could be
  sure of the heritage of the new plants.

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Mendel

• Mendel worked with his plants until he was sure
  he had true breeding varieties-- that is,
  varieties for which self fertilization produced
  offspring all identical to the parent. In other
  words, a pure-bred plant).
• For instance, he identified a purple flowered
  variety that produced offspring plants that all
  had purple flowers.

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Hybridization

• Now Mendel was ready to ask what would happen
  when he crossed his different true breeding
  varieties with each other.
• For example, what offspring would result if
  plants with purple flowers and plants with white
  flowers were cross fertilized?
• In the language of the plant and animal breeders
  and geneticists, the offspring of two different
  varieties are called hybrids, and the
  cross-fertilization itself is referred to as
  hybridization, or simply a cross.

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Hybridization

• The true breeding parental plants are called the
  P generation and their hybrid offspring are the
  F1 generation.
• The offspring of F1 plants are known as the F2
  generation.

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HEREDITARY PHYSICAL CHARACTERISTICS

• Genotype and Phenotype
• Genotype means the type of genes a person has, or
  their genetic make-up.
• Genes, the units of heredity that control the
  specific characteristics of an individual, are
  arranged in a linear fashion along the
  chromosomes.
• Alleles are a pair of genes on a pair of
  chromosomes that affect the same trait. For
  instance, both chromosomes have an allele for eye
  color, both have an allele for skin color, etc.

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HEREDITARY PHYSICAL CHARACTERISTICS

• Those genes that affect the same trait are called
  alleles.
• A dominant allele is given a capital letter, and
  a recessive allele is given the same letter in
  lower case.
• For instance, having an earlobe that is
  unattached to the face is a dominant trait, so we
  can call it E.
• An attached earlobe would then be called e.

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Alleles

• Alleles occur in pairs just as one pair of each
  type of chromosome is inherited from each parent,
  so too each pair of alleles are inherited from
  each parent.
• The allele which is traditionally indicated by an
  uppercase (capital) letter is the dominant trait.
  
• The allele which is traditionally indicated by a
  lowercase (small) letter is the recessive trait.

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Homozygous

• If a sperm cell has e and the egg cell has e, the
  offspring must have ee.
• That is called homozygous (pure) recessive.
• That means the person would have an attached
  earlobe.
• If a sperm cell has E and the egg cell has E, the
  offspring must have EE.
• This is called homozygous (pure) dominant. That
  means the person would have an unattached earlobe.

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Homozygous

• The term for pure is homo. It refers to
  something being the same.
• In the old days, you had to shake up milk because
  the cream would rise to the top. Nowadays, people
  want less fat, so the cream is removed before you
  get it this is called homogenized milk.
• A homogenized mixture is one that is the same
  throughout, and requires no periodic mixing.
• Therefore, when the allele pairs are either EE or
  ee, they are homozygous.

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Heterozygous

• The opposite of homo is hetero, so an allele
  pair that is Ee is heterozygous.
• If one of the sex cells has E and the other sex
  cell has e, what will the offspring have? Ee.
• What type of earlobe will they have? Unattached.
  Why? Because the dominant trait is stronger, so
  if it is present at all, it will manifest.

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Phenotype

• The physical appearance of a person is called the
  phenotype.
• A person with Ee will therefore be called a
  heterozygous genotype, with an unattached earlobe
  phenotype.

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Sample Problems

• What earlobe alleles will a person have who is
  homozygous recessive? ee
• What earlobe alleles will a person have who is
  homozygous dominant? EE
• What earlobe alleles will a person have who is
  heterozygous? Ee

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Figuring the Odds

• If one of the parents is homozygous dominant
  (EE), the chances of their having a child with
  unattached earlobes is 100 , because this parent
  has only a dominant allele (E) to pass on to the
  offspring.
• On the other hand, if both parents are homozygous
  recessive (ee), there is a 100 chance that each
  of their children will have attached earlobes.

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Figuring the Odds

• However, if both parents are heterozygous, then
  what are the chances that their child will have
  unattached or attached earlobes?
• To solve a problem of this type, it is customary
  first make a table (Punnet Square) of the
  genotype of the parents and their possible
  gametes.

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Punnet Square
E e
E
e
E e
E EE Ee
e Ee ee
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Figuring the Odds

• That means that when Harry meets Sally, their
  child has a 25 chance (13) of being ee, and 25
  chance of being EE, and 50 chance (11) of being
  Ee.
• But thats just the genotype. What about the
  phenotype (what will the child look like)?
• There is a 75 chance (31) of having an
  unattached earlobe (Ee or EE).
• There is a 25 chance (13) of having an attached
  earlobes (ee).

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Sample Test Questions

• In crossing a heterozygous parent and a
  homozygous recessive parent, what is the percent
  chances that an offspring will receive a dominant
  allele?
• Answer 50

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Sample Test Questions

• What is the ratio of the phenotype for crossing
  two heterozygous parents for ear lobe attachment?
• What is the ratio of the genotype for crossing
  two heterozygous parents for ear lobe attachment?

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121
The first number represents EE, the second number
is Ee, the third is ee
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Sample Test Questions

• Free earlobes (E) are dominant over attached
  earlobes (e).
• If two people with homozygous attached earlobes
  mate, what will be the phenotype of their
  offspring?
• All attached earlobes

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Sample Test Questions

• What is the ratio for crossing a heterozygous
  parent for ear lobe attachment and a homozygous
  recessive parent
• 11

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Sample Test Questions

• In crossing two heterozygous parents, what are
  the chances (in percent) for a pure recessive
  offspring?
• 25

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• For calculating eye color, lets say the father
  has brown eyes (BB) and the mother has blue eyes
  (bb).
• Use the Punnet Square to calculate the odds of
  what the child will look like. The fathers
  alleles are written in the vertical column and
  the mothers on the horizontal.

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• When we fill in the squares, we see that all of
  the children will be heterozygous (Bb) genotype.
  What color eyes will the babies all have? Brown.
  Therefore, the phenotype of all the children will
  be brown-eyed.

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• What if the father had brown eyes but his
  genotype was Bb instead of BB and they had 4
  children?
• Two of their children would have the genotype Bb
  (heterozygous for brown eyes), and two of their
  children would have the genotype bb (homozygous
  for blue eyes). Therefore, there is a 50 chance
  that each child would have the phenotype of brown
  eyes and 50 chance that each child will have the
  phenotype of blue eyes.

b
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• What if both parents were heterozygous?
• One child would have the genotype BB, two would
  have the genotype Bb, and one would have the
  genotype bb. That means that three out of four
  children would have brown eyes and one would have
  blue eyes. Therefore, there is a 75 chance their
  child will have brown eyes and 25 chance they
  will have blue eyes.
• Another way to write this is that there is a 31
  ratio of brown eyed to blue eyed children.
• That would describe the phenotype (appearance),
  but the genotype would be written as
• 121

B
b
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PERSONAL PHENOTYPE ANALYSIS

• Everyone clasp your hands together and hold them
  in the air which thumb is on top? Thumb
  crossing is a genetic phenotype.

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PERSONAL PHENOTYPE ANALYSIS

• HANDEDNESS Do you write with your right or left
  hand? Left handedness is recessive.
• MID-DIGITAL HAIR do you have hair on the middle
  segment of your fingers and toes?
• HITCHHIKERS THUMB Make a fist with your thumb
  extended. Is there almost a 90 angel between the
  first two joints of your thumb? It is a recessive
  trait.
• THE LENGTH OF THE INDEX FINGER in comparison to
  your ring finger is influenced by your sex. A
  short index finger is dominant in males and
  recessive in females.
• COLOR BLINDNESS Look through the color-blindness
  testing books on the demonstration table. Can you
  distinguish the numbers and patterns on each
  page? About 8 of American males and 0.4 females
  are recessive for red and green color blindness.
• PTC TASTERS If you place a PTC test paper on
  your tongue for a minute, to some people it will
  taste bitter. Others do not taste anything.
  People who taste bitterness also tend to dislike
  broccoli and Brussels sprouts.
• SODIUM BENZOATE This is a food preservative
  taste this paper in the same way. Does it taste
  salty, sweet, sour, bitter, or not at all to you?
• NUTRASWEET Does this taste sweet or bitter to
  you?

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MAKE A BABY INSTRUCTIONS

• Now everyone is going to make a baby. Ready? Set?
  GO! (Just kidding)
• Use the Make a Baby Handout.
• Each of you should take a penny and work in
  pairs it doesnt matter if your partner is the
  opposite sex. There is a Data Table towards the
  end of the handout that you can record the
  characteristics of your baby. Record your names
  as parents on this data sheet. Then determine the
  sex of the child by flipping the coin. Give your
  child a name and record it. Every time you flip
  the coin, heads means a dominant trait, so write
  it down as a capital letter. Tails means it is a
  recessive trait, so write it down as a small
  letter. Each parent donates one gene (one letter)
  so the child has two letters. Then check the
  instructions to see what the babys letter
  combination represents.

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Getting Started

• 1. FACE SHAPE
• Flip your coin if its heads, write down a
  capital R, because you have donated a dominant
  characteristic to your baby. If it was tails,
  write down a small r because the gene you gave
  your baby is recessive. Then your partner flips
  the coin for face shape. If the two flips result
  in rr, then your baby has a round face. If the
  two flips were RR or Rr, your baby has a square
  face. Record this in your data table.
• Complete the rest of the traits to see what your
  baby looks like!

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REVIEW OF GENETICS

• Our nucleus contains 46 chromosomes (23 pairs). A
  chromosome is a double-stranded string of DNA.
  Stretched out, it is six feet long!
• DNA is made of a string of molecules called
  nucleic acids. There are only 4 different nucleic
  acids Adenine (A), Thymine (T), Guanine (G), and
  Cytosine (C).
• Each A, T, G, or C on one strand of DNA is paired
  to its counterpart on the other strand of DNA.
• Adenine (A) only pairs with Thymine (T), and
  Guanine (G) only pairs with Cytosine (C).
• When they pair up, they are called base pairs.
  There are about 250 million base pairs of nucleic
  acids on one chromosome!
• The double strand of DNA looks like a ladder. It
  is then twisted into a shape called a helix.
• Therefore, DNA is a double-stranded helix.

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• When the body needs a particular protein, the
  double-stranded DNA helix unwinds, just in the
  segment that contains the nucleic acid sequence
  (called a GENE) for that protein. The DNA strand
  that is copied is called the sense strand (or
  strand), and the other strand is called the
  antisense strand (or strand).
• The gene is copied in the nucleus and the copy is
  taken to the cytoplasm, then taken to a ribosome,
  which reads the nucleic acid sequence.
• Every three nucleic acids code for one particular
  amino acid. These amino acids are then linked in
  the proper order in the ribosome, and the protein
  is made.
• When a person has a genetic defect, it is because
  the nucleic acids are not in the exact right
  order. There may be one nucleic acid substituted
  for another. There may be a new nucleic acid
  inserted. There may be a nucleic acid deleted.
  These things will displace the rest of the
  nucleic acid sequence. Sometimes, just one amino
  acid in the wrong order will cause death in a
  person before they are born.

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• A gene is a particular sequence of nucleic acids
  on the DNA strand of the chromosome. The function
  of the genes on the DNA is to create an RNA
  strand that will tell a ribosome how to make a
  particular protein. Proteins carry out most of
  the functions of the body.
• TRANSCRIPTION is the process of DNA creating the
  RNA strand in the nucleus. The type of RNA it
  makes is called mRNA (messenger RNA). The gene on
  the DNA is like my hand. I want to duplicate my
  hand, so I make a clay mold of it. The clay mold
  is the messenger RNA molecule.
• This occurs in the nucleus.
• The mRNA then exits the nucleus through a pore
  and goes to the cytoplasm.

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• TRANSLATION is the process of mRNA is read by a
  ribosome, telling the ribosome what order to put
  the amino acids in. The amino acids become the
  protein. Therefore, translation is characterized
  by PROTEIN SYNTHESIS.
• This occurs in the cytoplasm.
• During translation, the mRNA (clay mold of my
  hand) has already left the nucleus and is now in
  the cytoplasm. The RNA presents its hand
  imprint to the ribosome. The ribosome fills the
  hand imprint with plaster to make a positive
  cast, or a duplicate of the original gene.

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• When the ribosome reads the copy of the gene (the
  nucleic acid sequence) that was made in the
  cytoplasm, every group of three nucleic acids is
  called a CODON. Each codon codes for one amino
  acid.
• For example, if the first three nucleic acids are
  G, C, T, when you check that code in a manual,
  you find that means the first amino acid is
  Alanine. If the next three nucleic acids are C,
  C, G, that codes for Proline. Therefore, the
  ribosome links alanine to proline, and so on,
  until the entire amino acid sequence is finished.
  
• This new protein is placed in an envelope for
  protection, and dumped into the endoplasmic
  reticulum. During its journey in the RER and then
  in the Golgi complex, protective molecular groups
  are placed around the delicate ends and side
  groups of the protein. After that, it is ready to
  start functioning.

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• TRANSCRIPTION VIDEO
• TRANSCRIPTION WEBSITE
• TRANSLATION VIDEO
• TRANSLATION WEBSITE
• DECODING A GENE
• DNA KIT PROJECT (Handout Do page one now)

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• Amino Acids build proteins
• Building blocks of protein, containing an amino
• group and a carboxyl group
• Amino acid structure central C amino group,
• acid group, and variable group

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• a) AMINO ACIDS are MONOMERS (building blocks) of
  protein. They are tiny carbon molecules, made of
  just a carbon atom and a few other atoms.
• There are only 22 standard types of amino acids
  in the human body (20 of them are involved in
  making proteins). Nine of these are essential
  amino acids, meaning that we have to get them in
  the diet. We can synthesize the others.
• Amino acids are like beads on a necklace. Each
  bead is an amino acid, and the whole necklace is
  the protein. A bunch of the same types of
  necklaces (proteins) woven together makes up our
  tissues.

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Amino Acids
Essential Nonessential
Histidine Alanine
Leucine Arginine
Isoleucine Asparagine
Lysine Aspartic acid
Methionine Cysteine
Phenylalanine Glutamic acid
Threonine Glutamine
Tryptophan Glycine
Valine Ornithine
Proline
Selenocysteine
Serine
Tyrosine

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Mutations of Genes

• Mutation change in the nucleotide base sequence
  of a genome rare
• Not all mutations change the phenotype
  (appearance)
• Two classes of mutations
• 1. Base substitution
• eg point mutation
• GTTCAAG - (normal)
• ATTCAAG - mutant (abnormal)
• Silent mutation
• No change in amino acid sequence

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Mutations of Genes

• Missense mutation
• New amino acid
• ALA-PHE-LEU-TRY-STOP
• PHE-PHE-LEU-TRY-STOP
• Non-sense mutation a stop codon is inserted
  into protein sequence
• Truncated protein
• ALA-PHE-STOP-TRY-STOP

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Mutations

• 2. Frameshift mutation
• Insertion or deletion of one or more bases
• Original sequence ATG CCA GGT AAG
• Insertion ATT GCC AGG TAA G
• Deletion ATC CAG GTA AG_
• If it happens at the end of a gene it may not be
  as bad

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Effects of Mutation
Figure 7.20
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Genetic Code
Figure 7.9
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DNA Handout do page 3 now

• Missense mutation eg. sickle cell
• results in a codon that codes for a different
  amino acid. The resulting protein may be
  nonfunctional
• Nonsense mutation eg Cystic fibrosis
• Stop codon is inserted, truncated protein
• Frameshift insertion eg. Tay-Sachs disease
• Frame shift deletion CCR5
• CCR5 is our cell membrane receptor that the HIV
  virus uses to attack. People with this genetic
  mutation are immune to many strains of the AIDS
  virus.

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Causes of mutations

• Spontaneous mutations
• Happens during replication
• More often in prokaryotes than eukaryotes.
• Eukaryotes have better repair mechanisms.

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Mutagens

• Radiation
• Ionizing radiation (x-rays) induces breaks in
  chromosomes
• Nonionizing radiation (UV light) induces
  thymine dimers
• Chemical Mutagens
• Nucleotide analogs disrupt DNA and RNA
  replication and cause point mutations
• Eg. 5-bromouracil pairs with guanine
• Caffeine not a strong mutagen but it does
  effect fetal development
• Alkylating agents- used for cancer treatment

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DNA Repair
Figure 7.24
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DNA Repair
Figure 7.24
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Radiation gigantism from the Fukushima disaster 

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  egation_id288381481237582

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Identifying Mutants, Mutagens, and Carcinogens

• DNA DAMAGE VIDEO
• TUMOR GROWTH VIDEO
• Mutants descendents of cell that does not
  successfully repair a mutation
• Wild types mutant cells normally found in
  nature
• Methods to recognize mutants
• Positive selection
• Survival of the fittest
• Negative (indirect) selection
• selective removal of rare alleles that are
  deleterious.

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Genetic Recombination and Transfer

• Recombination and transfer of genes occurs during
  exchange of DNA segments with those of another
  DNA segment
• Recombinants cells with DNA molecules that
  contain new nucleotide sequences
• Vertical gene transfer organisms replicate
  their genomes and provide copies to descendants
• Horizontal gene transfer donor contributes part
  of genome to recipient three types
• Transformation
• Transduction
• Bacterial Conjugation

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Transformation Experiments

• The transforming agent in the experiment was DNA
  became the evidence that DNA is genetic material
• Cells that take up DNA are competent.

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Griffiths Transformation Experiment
Figure 7.29
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Transduction

• Transduction is the process by which DNA is
  transferred from one bacterium to another by a
  virus.
• When bacteriophages (viruses that infect
  bacteria) infect a bacterial cell, their normal
  mode of reproduction is to harness the
  replication machinery of the host bacterial cell
  to make numerous virions, or complete viral
  particles, including the viral DNA or RNA and the
  protein coat.
• Transduction explains how antibiotic drugs become
  ineffective due to the transfer of resistant
  genes between bacteria.
• In addition, transduction experiments attempt to
  cure diseases such as Muscular Dystrophy.

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Generalized Transduction
Figure 7.30
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Bacterial Conjugation
Figure 7.31
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Bacterial Conjugation
Figure 7.31
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VIDEOS

• CELL SIGNALS VIDEO (13 mins)
• STEM CELLS VIDEO

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French police on hunt for serial rapist stumped
by identical twin suspects

• Police are holding both brothers while they run
  extensive genetic tests to try to distinguish
  between the two. The complicated tests could cost
  more than 1 million.
• The environment can change our DNA too. We all
  build up mutations in our DNA over time. Our DNA
  also changes in response to things like sunlight
  or the food we eat. 

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• These changes are pretty rare. Everyone has about
  100 new mutations in their DNA. Sounds like a lot
  but spread out over 3 billion base pairs, that is
  quite a needle in a haystack.
• Also, all of the changes aren't in all of your
  cells -- not all of your cells have the same DNA
  sequence! If a DNA mistake happens late in our
  development, then only a few cells will have that
  mutation. If a mistake happens early, then more
  cells will have the DNA change but still not all
  of them.
• The differences between identical twins increase
  as they age, because environmentally triggered
  changes accumulate. 

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Why do identical twins have different
fingerprints?

• While you were growing inside of your mother, you
  touched the amniotic sac.
• When you touched it during weeks 6-13, the
  patterns of your fingerprints were changed.
• This is why identical twins have different
  fingerprints.

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GENETIC DISORDERS

• 1. Chromosome Disorders
• 2. Sex Chromosomal Disorders
• 3. Dominant Disorders (only one dominate allele
  needs to be present)
• 4. Homozygous Recessive Disorders (both parents
  must have rr alleles)
• 5. Incompletely Dominant Traits
• 6. Sex-Linked Traits
• 7. Sex-Influenced Traits

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Down Syndrome

• Down syndrome is also called trisomy 21 because
  the persons chromosome number 21 has three
  chromosomes joined together instead of just two.
• The chances of a woman having a Down syndrome
  child increase rapidly with age, starting at
  about age 40.
• The frequency of Down syndrome is 1/ 800 births
  for mothers under 40 years of age, but women over
  40 are 10 times more likely to have a Down
  syndrome child.

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Down Syndrome

• Characteristics of Down syndrome include a short
  stature an eyelid fold stubby fingers a wide
  gap between the first and second toes a large,
  fissured tongue a round head a palm crease (the
  so-called simian line), and mental retardation,
  which can sometimes be severe.

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Down Syndrome
Their personalities are usually cheerful,
good-natured, and pleasant throughout their lives.
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Down Syndrome
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Amniocentesis

• Removing fluid and cells from the amniotic sac
  surrounding the fetus, followed by karyotyping
  can detect a Down syndrome child.
• Scientists have located genes most likely
  responsible for the increased tendency toward
  leukemia, cataracts, accelerated rate of aging,
  and mental retardation.
• One day it might be possible to control the
  expression of that gene even before birth so that
  at least this symptom of Down syndrome does not
  appear.

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Amniocentesis
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Cri du Chat Syndrome (cats cry)

• Cri du Chat Syndrome (cats cry)
• This is caused by one missing segment of
  chromosome 5 and occurs in 1/ 50,000 live births.
  An infant with this syndrome has a moon face,
  small head, and a cry that sounds like the meow
  of a cat because of a malformed larynx. An older
  child has an eyelid fold and misshapen ears that
  are placed low on the head. Severe mental
  retardation becomes evident as the child
  matures.

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Cri Du Chat Syndrome
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Sex Chromosomal Disorders

• All of the cells in our body have all of our
  chromosomes in the nucleus except for the egg and
  the sperm.
• Each of these has all of our chromosomes in the
  nucleus, except there is only one of the two sex
  chromosomes.
• Since women are XX, all of her egg cells are X,
  but since males are XY, a sperm can bear an X or
  a Y.
• Therefore, the sex of the newborn child is
  determined by the father.
• If a Y- bearing sperm fertilizes the egg, then
  the XY combination results in a male.
• On the other hand, if an X-bearing sperm
  fertilizes the egg, the XX combination results in
  a female.

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Chromosomal Disorders

• All factors being equal, there is a 50 chance of
  having a girl or a boy.
• If a couple has 10 children and they are all
  boys, what is the chance that an eleventh child
  is going to be a boy?
• Interestingly, the death rate among males is
  higher than for females.
• By age 85, there are twice as many females as
  males.

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Jacob syndrome

• occurs in 1/ 1,000 births.
• These XYY (an extra male chromosome) males are
  usually taller than average, suffer from
  persistent acne, and tend to have speech and
  reading problems.
• At one time, it was suggested that these men were
  likely to be criminally aggressive, but it has
  since been shown that the incidence of such
  behavior among them may be no greater than among
  XY males.

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Jacob Syndrome XYY
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Klinefelter syndrome

• occurs in 1/ 1,500 births.
• These males with XXY (an extra female chromosome)
  and they are sterile.
• They are males with some female characteristics.
• The testes are underdeveloped, they have some
  breast development, and there is no facial hair.
• They are usually slow to learn but not mentally
  retarded.

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Klinefelter syndrome
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Klinefelter syndrome XXY
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Triple-X syndrome

• occurs in 1/ 1,500 births.
• These are females with an extra female
  chromosome XXX.
• You might think they are especially feminine, but
  this is not the case.
• Most have no physical abnormalities except that
  they may have learning disabilities, menstrual
  irregularities, including early onset of
  menopause.

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Triple-X syndrome
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Turner syndrome

• occurs in 1/ 6,000 births.
• The individual is XO, meaning one of the sex
  chromosomes is missing.
• These are females and have a short, broad chest,
  and webbed neck.
• The ovaries and uterus are nonfunctional. Turner
  females do not undergo puberty or menstruate, and
  there is a lack of breast development.
• They are usually of normal intelligence and can
  lead fairly normal lives, but they are infertile
  even if they receive hormone supplements.

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Turners Syndrome
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Turner syndrome XO
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Dominant Disorders Neurofibromatosis

• Used to be known as Elephant Man disease, this is
  one of the most common genetic disorders.
• It affects roughly 1/ 3,000 people.
• It is seen equally in every racial and ethnic
  group throughout the world.
• At birth or later, the affected individual may
  have six or more coffee with milk colored spots
  (known as cafe-au-lait) on the skin.
• Such spots may increase in size and number and
  may get darker.
• Small benign tumors (lumps) called neurofibromas
  may occur under the skin or in various organs.

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Neurofibromatosis
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Neurofibromatosis
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Neurofibromatosis

• In most cases, symptoms are mild, and patients
  live a normal life.
• In some cases, however, the effects are severe.
• Skeletal deformities, including a large head, are
  seen, and eye and ear tumors can lead to
  blindness and hearing loss.
• Many children with neurofibromatosis have
  learning disabilities and are hyperactive.
• The abnormal gene is on chromosome 17.

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Dominant Disorders

• Huntington Disease
• This affects 1/ 20,000 people.
• It is a dominant neurological disorder that leads
  to progressive degeneration of brain cells,
  which causes severe muscle spasms and personality
  disorders.
• Most people appear normal until they are of
  middle age and have already had children who
  might also be stricken.
• There is no effective treatment, and death often
  comes ten to fifteen years after the onset of
  symptoms.

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Huntingtons Disease
107
Homozygous Recessive Disorders Tay - Sachs
disease

• This disease usually occurs among Jewish people.
• At first, it is not apparent that a baby has
  Tay-Sachs disease.
• However, development begins to slow down between
  four months and eight months of age, and
  neurological impairment and psychomotor
  difficulties then become apparent.
• The child gradually becomes blind and helpless,
  develops uncontrollable seizures, and eventually
  becomes paralyzed.
• There is no treatment or cure for Tay-Sachs
  disease, and most affected individuals die by the
  age of three or four.
• It is caused by a genetic enzyme deficiency.

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Tay - Sachs disease
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Cystic Fibrosis

• This is the most common lethal genetic disease
  among Caucasians in the United States.
• About 1 in 20 Caucasians is a carrier, and about
  1/ 2,500 births have the disorder.
• In these children, the mucus in the bronchial
  tubes is particularly thick and interferes with
  breathing, and the lungs get infected frequently.
• New treatments have raised the average life
  expectancy to 37 years of age.
• The cystic fibrosis gene is located on chromosome
  7.

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Cystic Fibrosis
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Phenylketonuria (PKU)

• This occurs in 1 / 5,000 births, so it is not as
  frequent as the disorders previously discussed,
  however, PKU is tested for in routine blood
  screenings of all newborns in the United States.
• This is the disease that offspring of first
  cousins are more likely to get.
• PKU people lack an enzyme that is needed to break
  down an amino acid (phenylalanine), and so the
  amino acid accumulates in the urine.
• These people have to have a special diet that
  does not contain that amino acid.
• If they get too much of it, they will get
  neurological problems and mental retardation.
• Thats why nutrition labels have to warn when
  they contain phenylalanine.

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PKU
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Incompletely Dominant Traits

• Incomplete dominance is exhibited when there is
  an intermediate phenotype.
• These people can be carriers of a disorder
  without being sick themselves.
• Their children may have the disorder, or they
  also may be carriers.
• When they are carriers, they are said to have the
  trait of the disorder, but not the disease.

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Sickle-Cell Disease

• This is an incompletely dominant disorder.
• In persons with sickle-cell disease, the red
  blood cells arent round disks like normal red
  blood cells they are irregular.
• In fact, many are sickle shaped, like a banana
  with points on both ends.
• The red blood cells do not carry oxygen well, and
  they get stuck in arteries also. Therefore,
  people with this disease suffer from poor
  circulation, anemia, poor resistance to
  infection, internal bleeding, pain in the abdomen
  and joints, and damage to internal organs.
• SICKLE CELL VIDEO

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Sickle-Cell Disease
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Incompletely Dominant Traits

• Sickle-Cell Disease
• In malaria-infested Africa, infants with
  sickle-cell disease die (they got a bad
  chromosome from both parents), but infants with
  sickle-cell trait (they got a bad chromosome from
  only one parent) actually have better resistance
  to malaria than a normal human being. The malaria
  parasite normally reproduces inside red blood
  cells. But a red blood cell of a sickle-cell
  trait infant kills the parasite.
• Therefore, the only people who survive well in
  Africa are those with sickle cell trait. Thats
  why about 60 of the population in
  malaria-infested regions of Africa has sickle
  cell trait. Unfortunately, 25 of their offspring
  can get the sickle cell disease.

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Malaria
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Sex-Linked Traits

• Traits controlled by alleles on the sex
  chromosomes are said to be sex-linked an allele
  that is only on the X chromosome is X-linked, and
  an allele that is only on the Y chromosome is
  Y-linked.
• Most sex-linked alleles are on the X chromosome
  since it is larger.

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X-Linked Disorders

• X-linked conditions can be dominant or recessive,
  but most known are recessive.
• More males than females have the trait.
• If a male has an X-linked condition, his
  daughters are often carriers, so her male
  children are also likely to have the condition.
• All of the following disorders are sex-linked.

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Male Pattern baldness

• From a gene that is inherited from the mother.
• For you guys, if your mothers father was bald,
  you are more likely to be bald.
• It doesnt matter if your father is bald or if
  his father is bald.
• You get the baldness gene from your mothers
  father.

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X-linked Recessive Disorders

• Three well-known X-linked recessive disorders
  (more common in males than females) are color
  blindness, muscular dystrophy, and hemophilia.

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Color Blindness

• In the human eye, there are three different types
  of cone cells (remember, they sense color
  vision).
• These different types are sensitive to either the
  color red, green, or blue.
• The gene for the red and green cells is on the X
  chromosome.

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COLOR BLINDNESS TEST

• About 8 of Caucasian men have red-green color
  blindness.
• Opticians have special charts by which they
  detect those who are color blind.

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Muscular Dystrophy

• As you can tell by the name, this disease is
  characterized by a wasting away of the muscles.
• The most common form is X-linked and occurs in
  about 1/ 3,600 male births.
• Symptoms, such as waddling gait, toe walking,
  frequent falls, and difficulty in rising, may
  appear as soon as the child starts to walk.
• Muscle weakness progresses to the point where
  they need a wheelchair.
• Death usually occurs by age 20 therefore,
  affected males are rarely fathers.
• The disease is from a carrier mother to carrier
  daughter.

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Muscular Dystrophy
127
Hemophilia

• About 1/10,000 males is a hemophiliac.
• It is due to the absence of a clotting factor.
• It is called the bleeders disease because the
  blood does not clot.
• Every time they get a bruise, they have to have
  either a blood transfusion or an injection of a
  clotting protein, which they keep in their
  refrigerator since they need it so often.

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X-Linked Disorders

• In the early 1900s, hemophilia was prevalent
  among the royal families of Europe, and all of
  the affected males could trace their ancestry to
  Queen Victoria of England.
• Of her 26 grandchildren, five grandsons had
  hemophilia and four granddaughters were carriers.
  
• Because none of Queen Victorias ancestors or
  relatives were affected, it seems that the faulty
  allele she carried arose by mutation either in
  Victoria or in one of her parents.

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Hemophilia
130

• Her carrier daughters, Alice and Beatrice,
  introduced the gene into the ruling houses of
  Russia and Spain, respectively. Alexis, the last
  heir to the Russian throne before the Russian
  Revolution, was a hemophiliac. There are no
  hemophiliacs in the present British royal family
  because Victorias eldest son, King Edward VII,
  did not receive the gene and therefore could not
  pass it on to any of his descendants.

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Sex-Influenced Traits

• The length of the index finger is sex-influenced.
  
• In females, an index finger longer than the
  fourth finger (ring finger) is dominant.
• In males, an index finger longer than the fourth
  finger seems to be recessive.

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Stem Cell Research
134
Stem Cell Research

• Some human illnesses, such as diabetes type 1,
  Alzheimer disease, and Parkinson disease, are
  clearly due to a loss of specialized cells. In
  diabetes type 1, there is a loss of insulin
  secreting cells in the pancreas, and in Alzheimer
  disease and Parkinson's disease there is a loss
  of brain cells. Specific types of cells are
  needed to cure these conditions.

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Stem Cell Research

• Stem cells are cells that continuously divide to
  produce new cells that go on to become
  specialized cells. The bone marrow of adults and
  the umbilical cord of infants contain stem cells
  for each type of blood cell in the body. It is
  relatively easy to retrieve blood stem cells from
  either of these sources. Researchers report that
  they have injected blood stem cells into the
  heart and liver only to find that they became
  cardiac cells and liver cells respectively!

136
Stem Cell Research

• The skin, gastrointestinal lining, and the brain
  also have stem cells, but the technology to
  retrieve them has not been perfected. Also, it
  has not been possible to change adult stem cells
  into a fully developed specific type of cell
  outside the body. If the technique is perfected,
  it might be possible to change a brain stem cell
  and to the type of cell needed by a Parkinson
  patient.

137
Stem Cell Research

• Today, young, relatively infertile couples seek
  assistance in achieving pregnancy and having
  children. During in vitro fertilization, several
  eggs and sperm are placed in laboratory glass,
  where fertilization occurs and development
  begins. A physician places two or three embryos
  in the woman's uterus for further development,
  but may hold back some in case these fail to take
  hold. Embryos that are never used remain frozen
  indefinitely unless they are made available to
  researchers.

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Stem Cell Research

• Each cell of an embryo is called an embryonic
  stem cell because it can become any kind of
  specialized cell in the body.
• Researchers have already used non-human embryonic
  cells to create supplies of nonhuman specialized
  cells.
• Therefore, they think the same will hold true
  with human embryonic stem cells.
• If so, medicine would undergo an advancement of
  enormous proportions.

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Stem Cell Research

• Even so, there is a down side.
• What about the embryos that had been forced to
  give up the chance of becoming an adult in order
  to extend the health span of those already
  living? Would this be ethical?

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Stem Cell Research

• In Great Britain, researchers can work with
  embryos that are 14 days or younger because
  embryos usually implant in the uterus around day
  14. However, some people beleive that all human
  beings are equal, and ought not to be harmed or
  considered to be less than human on the basis of
  age or size or stage of development or condition
  of dependency. They believe that embryos should
  not be used as a means to an end, even good ends,
  such as a cure for diseases or to save another
  human life.

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Stem Cell Research

• President George W. Bush agreed and signed an
  executive order that forbids the use of federal
  funds for the purpose of creating new cell lines
  derived from embryos in United States. The order
  does not affect any embryonic stem cell lines
  previously established nor any work with adult
  stem cells. Nevertheless, some researchers have
  left the United States to work in countries where
  stem cell research is freely allowed without
  governmental restrictions.

142
Stem Cell Research

• Stem cell research is a bioethical dilemma. Some
  say that to think in dualistic terms is not
  helpful it isn't that an embryo is a human being
  or is not a human being, it's that a fully
  developed human being comes about gradually. For
  instance, what would you do if there was a fire
  in a fertility clinic and you were faced with the
  choice of saving a five-year-old girl or a tray
  of 10 embryos? Which would you choose? Some
  people also believe that stem cell research is
  ethical, but that humans should not be cloned.

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Stem Cell Research

• Should researchers have access to embryonic stem
  cells or only adult stem cells? What is your
  reasoning?
• Do you believe that while it is ethical to do
  research with embryonic stem cells to cure human
  illnesses, it is not ethical to clone humans?
  What is your reasoning?
• Some researchers are mixing nonhuman with human
  embryonic stem cells in order to study
  developmental differences. Is this ethical?

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•  You can get a complete gene map of your unborn
  child -- but should you?
• http//fxn.ws/OsO6tY

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Genetic Testing for Cancer Genes
146
Genetic Testing for Cancer Genes

• Several genetic tests are now available to detect
  certain cancer genes. If a woman tests positive
  for a particular type of defective gene, they
  have an increased risk for early onset breast and
  ovarian cancer. If an individual tests positive
  for a different type of gene, they are at greater
  risk for the development of colon cancer. Other
  genetic tests exist for rare cancers as well.

147
Genetic Testing for Cancer Genes

• Advocates for genetic testing say that it can
  alert those who test positive for these mutated
  genes to undergo more frequent mammograms or
  colonoscopies. Early detection of cancer clearly
  offers the best chance for successful treatment.
  Others feel that genetic testing is unnecessary
  because nothing can presently be done to prevent
  the disease. Perhaps it is enough for those who
  have a family history of cancer to schedule more
  frequent checkups beginning at a younger age.

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Genetic Testing for Cancer Genes

• People opposed to genetic testing worried that a
  woman with a defective gene for breast cancer
  might make the unnecessary decision to have a
  radical mastectomy. In a study of 177 patients
  who underwent gene testing for susceptibility to
  colon cancer, less than 20 received any
  counseling before the test. Moreover, physicians
  misinterpreted the test results in nearly one
  third of the cases.

149
Genetic Testing for Cancer Genes

• It's possible, too, that people who test negative
  for a particular gene may believe that they are
  not at risk for cancer. This might encourage
  them not to have routine cancer screening.
• Regular testing and avoiding known causes of
  cancer such as smoking, a high fat diet, or too
  much sunlight, are important for everyone.

150
Genetic Testing for Cancer Genes

• Should everyone be aware that genetic testing for
  certain cancers is a possibility, or should such
  testing the confined to a research setting?
• If genetic testing for cancer were offered to
  you, would you take advantage of it? Why or why
  not?
• Are protective measures to avoid cancer more
  important than testing? Explain.

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Choosing Gender
152
Choosing Gender

• You may feel that it is ethically wrong to choose
  which particular embryo can continue to develop
  following in vitro fertilization.
• But what about choosing whether an X-bearing or
  Y-bearing sperm should fertilize the egg?
• As you know, the sex of a child depends upon
  whether an X-bearing sperm or a Y-bearing sperm
  enters the egg.

153
Choosing Gender

• A new technique has been developed that can
  separate each type of sperm. First, the sperm
  are dosed with a chemical. The X-chromosome has
  slightly more DNA than the Y-chromosome, so it
  takes up more dye. When a laser beam shines on
  the sperm, the ex-bearing sperm shine a little
  more brightly. A machine sorts the sperm into
  two groups on this basis. The results are not
  perfect. Following artificial insemination,
  there is about an 85 success rate for a girl in
  about a 65 rate for a boy.

154
Choosing Gender

• Some might believe that this is the simplest way
  to make sure they have a healthy child if the
  mother is a carrier of an X-linked genetic
  disorder such as hemophilia or muscular
  dystrophy. Previously, a pregnant woman with
  these concerns had to wait for the results of an
  amniocentesis test and then decide whether or not
  to abort the pregnancy if it was a boy. Is it
  better to increase the chances of a girl to begin
  with? Or, do you believe that gender selection
  is not acceptable for any reason?

155
Choosing Gender

• Even if it does not lead to a society with far
  more members of one sex than another, there could
  be a problem. Once you separate reproduction
  from the sex act, it might open the door to
  genetically designing children in the future. On
  the other hand, is it acceptable to bring a child
  into the world with a genetic disorder that may
  cause an early death or a lifelong disability?
  Would it be better to select sperm for girl, who
  at worst would be a carrier like her mother?

156
Choosing Gender

• Do you think it is acceptable to choose the
  gender of a baby? Even if it requires artificial
  insemination at a clinic? Why or why not?
• Do you see any difference between choosing gender
  or choosing embryos free of a genetic disease for
  reproduction purposes?
• If selecting sperm is less expensive than
  selecting embryos, should women who are carriers
  of X-linked genetic disorders he encouraged to
  use this method of producing children who are
  free of the disease?

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Designer Children
158
Designer Children

• Human beings have always attempted to influence
  the characteristics of their children. For
  example, couples have attempted to determine the
  sex of their children for centuries through a
  variety of methods. Amniocentesis has allowed us
  to test fetuses for chromosomal abnormalities and
  debilitating developmental defects before birth.
  Modern genetic testing technology enables parents
  to directly select children bearing desired
  traits, even at the very earliest stages of
  development.

159
Designer Children

• Recently, a couple selected an embryo because, as
  a newborn, the individual could save the life of
  his sister.
• The couple, Jack and Lisa Nash, had a daughter
  with Fanconi's anemia, a rare inherited disorder
  in which affected persons cannot properly repair
  DNA damage that results from certain toxins.
• The disease primarily afflicts the bone marrow,
  and therefore results in a reduction of all types
  of blood cells.

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Designer Children

• Anemia occurs, due to a deficiency of red blood
  cells.
• Patients are also at high risk of infection,
  because of low white blood cell numbers, and of
  leukemia, because white blood cells cannot
  properly repair any damage to their DNA.

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Designer Children

• Fanconi's anemia may be treated by a traditional
  bone marrow transplant, or by an adult stem cell
  transplant, preferably from a parent or a
  sibling, because the risk of rejection is lower.
  Adult stem cells are almost always the preferred
  treatment option, because stem cells are hardier
  and much less likely to be rejected in a bone
  marrow transplant. The umbilical cord of a
  newborn is a rich source of adult stem cells for
  all types of blood cells.

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Designer Children

• The selection of an embryo on the basis of genes
  is accomplished by extracting a sample of the
  DNA, determining its sequence, and comparing it
  with known sequences for diseases. In this case,
  doctors examined the DNA of embryos to see if
  they had the gene in question, that the newborn
  would be healthy, and also would be able to
  benefit his sister. The parents underwent in
  vitro fertilization, and the 15 resulting embryos
  were screened to see if they were both free of
  the inherited disease in a match for their
  daughter.

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Designer Children

• Two embryos met these requirements, but only one
  implanted in the uterus and it developed into a
  healthy baby boy. Adult stem cells were
  harvested from the umbilical cord of the newborn
  and were successfully used to treat his sister's
  anemia. The physician who performed the genetic
  screening stated that he has received numerous
  inquiries about performing the procedure for
  other couples with diseased children

164
Designer Children

• This case, and other related cases, has raised a
  number of ethical issues surrounding prenatal
  selection of children based on genetic traits.
• While the AMA insists that selection based on
  traits not related to the disease is unethical,
  the AMA made an exception for this case, because
  the child was selected for medical reasons.

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Designer Children

• Still, some people believe that it is dangerous
  to bear children for the purpose of curing
  others, and that it should be compared with a new
  form of biological slavery.
• Others think that, soon, children will be
  selected for less altruistic reasons, such as for
  their height, physical prowess, or intellectual
  abilities.

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Designer Children

• In general, do you think it is ethical to have
  children to cure medically related conditions,
  regardless of how fertilization occurs? If not,
  do you agree with the AMA that this case is an
  acceptable exception?
• Because the brother was created as a treatment
  for his sister's disease, do you believe that
  there is a moral obligation to provide him with
  compensation?

167
Designer Children

• Would embryonic stem cells, derived from an
  aborted fetus and cultured in the laboratory, be
  an acceptable substitute?
• Would you willingly donate sperm or eggs for in
  vitro fertilization to produce a healthy child
  for a couple who could not have one because of
  the risk of an inherited disease, such as
  Fanconi's anemia?

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Designer Children
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Designer Children
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Designer Children
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Designer Children
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Designer Children
173
Reproductive and Therapeutic Cloning
174
Reproductive and Therapeutic Cloning

• Reproductive cloning and therapeutic cloning are
  done for different purposes. In reproductive
  cloning, the desired end is an individual that is
  genetically identical to the original individual.
  At one time, it was thought that the cloning of
  adult animals would be impossible because
  investigators found it difficult to have the
  nucleus of an adult cell start over, even when it
  was placed in an egg without a nucleus.

175
Reproductive and Therapeutic Cloning

• In March 1997, Scottish investigators announced
  they had cloned a sheep called Dolly.
• How was their procedure different from all the
  others that had been attempted?
• Unlike other attempts, the donor cells were
  starved which caused them to stop dividing and go
  into a resting stage, and this made the nuclei
  receptive to cytoplasmic signals for initiation
  of development.

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Reproductive and Therapeutic Cloning

• By now, and it is common practice to clone all
  sorts of farm animals that have desirable traits
  and even to clone the rare animals that might
  otherwise become extinct.

177
Reproductive and Therapeutic Cloning

• In the United States, no federal funds can be
  used on experiments to clone human beings.
  Cloning is wasteful-- even in the case of Dolly,
  out of 29 clones, only one was successful. Also,
  there is concern that cloned animals may not be
  healthy. Dolly was euthanized in 2003 because
  she was suffering from lung cancer and crippling
  arthritis. She had lived only half the normal
  lifespan for her species of sheep.

178
Reproductive and Therapeutic Cloning

• In therapeutic cloning, the desired end is not an
  individual rather, it is mature cells of various
  cell types.
• The purpose of therapeutic cloning is to learn
  more about how specialization of cells occurs and
  to provide cells and tissues that could be used
  to treat human illnesses such as diabetes, spinal
  cord injuries, and Parkinson disease.

179
Reproductive and Therapeutic Cloning

• There are two possible ways to carry out
  therapeutic cloning. The first way is to use the
  exact same procedure as reproductive cloning,
  except embryonic cells are separated and each one
  is subjected to treatment that causes it to
  develop into a particular type of cell such as
  red blood cells, muscle cells, or nerve cells.
  Some have ethical concerns about this type of
  therapeutic cloning, which is still very
  experimental, because if the embryo were allowed
  to continue development, it would become an
  individual.

180
Reproductive and Therapeutic Cloning

• The second way to carry out therapeutic cloning
  is to use adult stem cells.
• Stem cells are found in many organs of the adults
  body for example, the skin has stem cells that
  constantly divide and produce new skin cells.
• The bone marrow has stem cells that produce new
  blood cells as does the umbilical cord of
  newborns.

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Reproductive and Therapeutic Cloning

• It has already been possible to use stem cells
  from the brain to regenerate nerve tissue for the
  treatment of Parkinson's disease.
• However, the goal is to develop techniques that
  would allow scientists to turn any adult stem
  cell into any type of specialized cell.
• Many investigators are engaged in this endeavor.
  In order to do this, scientists need to know how
  to control gene expression.

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