-%20The%20Human%20Genome

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Chapter 14

• - The Human Genome

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14-1 Human Heredity

• The children in this family have some traits that
  are similar to their mothers and some that are
  similar to their fathers.

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• Can you predict chin shape?
• Procedure
• Two parents with cleft chins, both heterozygous
  for cleft chin (Cc), have three children with
  cleft chins. The parents are sure that their
  fourth child will not have a cleft chin. Draw a
  Punnett square to see if this is possible.
• Determine the probability that the fourth child
  will have a cleft chin. _________

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Human Heredity

• Human Chromosomes
• Make us who we are.
• This is the genetic information (DNA) which is
  inside the human cell.

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• To look at these chromosomes, biologists,
  photograph cells in mitosis.
• Mitosis is when the cell nucleus divides and the
  chromosomes are easier to see.
• Biologists then take these photographs and group
  them together in pairs.
• This picture of chromosomes arranged in this way
  is called a karyotype

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Karyotype
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• The human body contains 46 chromosomes
• 23 (sperm)
• 23 (egg)
• Together this forms a diploid zygote
• 46 total chromosomes

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Sex Chromosomes and Autosomes

• Sex chromosomes
• Only 2 of the 46
• Determine if someone is male or female
• Female XX
• Male XY
• Autosomes
• Remaining 44 chromosomes

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Human Traits

• Human traits are inherited
• Gregor Mendel
• Pedigree chart
• A pedigree shows a relationship within a family
• A pedigree chart follows one specific trait in a
  family

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Cleopatras Pedigree Chart
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Russian Royal Family Pedigree Chart
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Polygenic

• Some traits are actually polygenic
• Controlled by two or more genes
• Shape of your eyes
• Shape of your ears
• Eye color

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Other Trait Influences

• Environment
• Nutrition
• Exercise
• Your parents might both be 6 feet tall, but if
  they dont feed you, you are unlikely to grow to
  be 6 feet tall.

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Human Genes

• Our complete set of genetic information is our
  genome
• 30,000 genes
• Blood Group Genes
• Knowing a persons blood group is critical
  because using a wrong blood type could be life
  threatening
• Rh
• ABO
• Are two genes that are part of your blood type

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Rh

• Rhesus Monkey
• 2 alleles that determine blood type
• Rh is dominant Rh- is recessive
• A person with 2 positive alleles is Rh
• A person with a positive and a negative allele is
  RH
• A person with 2 negative alleles is Rh-

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ABO

• There are 3 alleles that determine blood type
• IA, IB and i
• Two of these alleles are codominant and one is
  recessive.
• Blood type is dependant upon what the antigens
  are on the surface of the red blood cells
• Type A blood lAlA, or IAi
• Type B blood IBIB or IBi
• Type AB blood IAIB
• Type O blood ii

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• Based on what you know of blood types which one
  of Mr. Mrs. Lopezs four kids must have been
  adopted? _____________

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Recessive Alleles

• Studying genetic disorders have helped us
  understand how human genes work
• Many of these disorders are caused by recessive
  alleles

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Phenylketonuria (PKU)

• People with this disorder lack the enzyme needed
  to break down Phenylalanine
• Causes
• A build-up of phenylalanine in tissues
• Mental retardation
• Can be controlled by a special diet
• All babies in US are tested for this at birth

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Tay-Sachs Disease

• Nervous system breakdown
• Infant death

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Albinism

• Lack of pigment in skin, hair, and eyes

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Cystic Fibrosis Galactosemia

• Excess mucus in lungs, digestive tract, and liver
  
• Susceptibility to infections
• Death in early adulthood if not treated

• Inability to digest the sugar galactose.
• Causes mental retardation, eye and liver damage

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Cystic Fibrosis
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Dominant Alleles

• Not all genetic disorders are caused by recessive
  alleles
• If you have a dominant allele for a genetic
  disorder, it will be expressed even if you also
  have a normal recessive allele
• Achondroplasia
• Huntingtons disease
• Hypercholesterolemia

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Achondroplasia

• Dwarfism

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Huntingtons Disease

• Mental deterioration and uncontrollable movements

Hypercholesterolemia

• Excess cholesterol in blood
• Heart disease

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Gene Expression

• In certain diseases, a small change in the DNA of
  a single gene affects the structure of a protein,
  causing a serious genetic disorder
• Cystic fibrosis
• Sickle cell anemia

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Sickle Cell Anemia

• Abnormal hemoglobin produced because of a single
  amino acid change in the hemoglobin protein
• Causes the RBCs to deform which causes clogging
  in the capillaries

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Sickle Cell Anemia
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Sex-Linked Genes
14-2 Human Chromosomes

• Because the X and Y chromosomes determine sex,
  genes located here are said to be sex-linked
  genes
• More than 100 sex-linked genetic disorders have
  been mapped to the X chromosome
• Males have just one X chromosome. Thus, all
  X-linked alleles are expressed in males, even if
  they are recessive

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Sex-Linked Genes

• Genes that are found on the X or Y chromosome.
• More genes are found on the X chromosome than the
  Y

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Colorblindness

• Three genes associated with color vision are
  found on the X chromosome
• Males are more often colorblind because they only
  have one X chromosome

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Colorblindness Test
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Colorblindness

• All X-linked alleles are expressed in males even
  if they are recessive

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Examples of X-linked Recessive Disorders

• Hemophilia blood-clotting disorder
• Duchenne Muscular Dystrophy
• Ichtyosis scaly skin
• Norrie Disease abnormal growth of retina
• Rett Syndrome mental retardation

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Hemophilia
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Duchenne Muscular Dystrophy
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X-Chromosome Inactivation

• Females have 2 X chromosomes and males only one.
  What to do?
• In all female cells, one X chromosome is randomly
  shut off.
• This causes some interesting problems if one X
  chromosome has a mutated gene

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Chromosomal Disorders

• Get too many or too few copies of a chromosome
• Caused by non-disjunction during meiosis
• Exs. Downs Syndrome Trisomy 21
• Turners Syndrome X_
• Klinefelters Syndrome XXY

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Downs Syndrome
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Turner Syndrome
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Kleinfelter Syndrome
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14-3 Human Molecular Genetics

• Human DNA Analysis
• Genetic tests are now available for hundreds of
  disorders.
• This can allow prospective parents to determine
  if they are carrying recessive alleles for a
  disorder.

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DNA Fingerprinting

• DNA is analyzed of by separating it into
  fragments
• This reveals a series of DNA bands of various
  sizes
• A pattern of bands is produced that can be
  distinguished from any other individual in the
  world (except for an identical twin).
• DNA samples can be obtained from blood, sperm,
  and hair strands that have tissue at their base.

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DNA Fingerprinting
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The Human Genome Project

• The Human Genome Project was an attempt to
  sequence all human DNA
• In June 2000, scientists announced that the Human
  Genome was complete.
• There is open availability of nearly all its
  data.
• You can use the Internet to read the latest
  genome data.

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Gene Therapy

• Gene Therapy is the process of changing the gene
  that causes a genetic disorder
• In gene therapy, an absent or faulty gene is
  replaced by a normal, working gene
• This way, the body can make the correct protein
  or enzyme it needs, which eliminates the cause of
  the disorder

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Gene Therapy
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Ethical Issues

• What will happen to the human species of we could
  design our bodies? What would be the
  consequences?
• Society will have to develop a thoughtful and
  ethical consensus of what should and should not
  be done with the Human Genome.