Nerve activates contraction

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MENDEL AND THE GENE IDEA
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Introduction
1. Mendel brought an experimental and
quantitative approach to genetics 2. By the law
of segregation, the two alleles for a character
are packaged into separate gametes 3. By the law
of independent assortment, each pair of alleles
segregates into gametes independently 4.
Mendelian inheritance reflects rules of
probability 5. Mendel discovered the particulate
behavior of genes
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Introduction

• The current theory for the mechanism for the
  transmission of genetic material was the
  blending hypothesis.
• This hypothesis proposes that the genetic
  material contributed by each parent mixes in a
  manner analogous to the way blue and yellow
  paints blend to make green.

• Mendel proposed an alternative model,
  particulate inheritance
• This proposes that parents pass on discrete
  heritable units - genes - that retain their
  separate identities in offspring.
• Genes can be sorted and passed on, generation
  after generation, in undiluted form.

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• Blending Hypothesis 1800s -suggested that
  traits of parents mix to form intermediate traits
  in offspring.
• Parents Offspring
• Red flower x White flower Pink flower
• Tall height x Short height Medium height
• Blue bird x Yellow bird Green birds
• Fair skin x dark skin Medium skin color
• If blending always occurred, eventually all
  extreme characteristics would disappear from the
  population.

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• Modern genetics began in an abbey garden, where a
  monk names Gregor Mendel documented mechanisms of
  inheritance.

Gregor Mendel Established genetics as a science
in 1860s. Considered the founder of modern
genetics.
1857
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mendel

• Mendel grew up on a small farm in what is today
  the Czech Republic.
• In 1843- entered monastery.
• He studied at the University of Vienna from 1851
  to 1853.
• The monks at this monastery had a long tradition
  of interest in the breeding of plants, including
  peas.
• Around 1857, Mendel began breeding garden peas to
  study inheritance.

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• Pea plants have several advantages for genetics.
• Pea plants are available in many varieties with
  distinct heritable features (characters) with
  different variants (traits).
• Short generation time, little space needed, cross
  or self fertilize

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Overview of Mendels experiments. -Mendel looked
at 7 traits-
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• Cross fertilization and self fertilization

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• He took a true breeding purple flower plant and
  crossed it with a true breeding white flower
  plant.
• He called these the parent generation (P
  generation)
• What do you think the offspring looked like?

Pollen
hybridize
X
ALL PURPLE
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Allowed to self-pollinate
F1
SAY WHAT???????
F2
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Mendel concluded

• Something is being passed from parent to
  offspring.
• He called these Factors
• Sometimes you can see it and sometimes you
  cant see it.
• If you can see it- it is dominant.(T)
• If its there and you cant see it- its
  recessive.(t)

Purple flower is a dominant trait and white
flower is a recessive trait.
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• Each Version of the factor, now known as gene, is
  called an Allele.

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Mendel developed a hypothesis to explain these
results that consisted of four related ideas.

• 1. Alternative versions of genes (different
  alleles) account for variations in inherited
  characters.
• Different alleles vary somewhat in the sequence
  of nucleotides at the specific locus of a gene

2. For each character, an organism
inherits two alleles, one from each
parent.

• 3. If two alleles differ, then
  one, the dominant allele, is
  fully expressed in the organisms
  appearance.
• The other, the recessive allele,
  has no noticeable effect on the
  organisms appearance.

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• 4. The two alleles for each character segregate
  (separate) during gamete production (meiosis).

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• Mendels quantitative analysis of F2 plants
  revealed the two fundamental principles of
  heredity the law of
  segregation the law of independent assortment.

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Law of segregation- the two alleles for a
character are packaged into separate gametes

• If the blending model were correct, the F1
  hybrids from a cross between purple-flowered and
  white-flowered pea plants would have pale purple
  flowers.
• Instead, the F1 hybrids all have purple flowers,
  just as purple as the purple-flowered parents.

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Law of segregation- the two alleles for a
character are packaged into separate gametes

• The white trait, absent in the F1, reappeared in
  the F2.
• Based on a large sample size, Mendel recorded in
  the F2 plants
• 705 purple-flowered
• 224 white-flowered
• 31 ratio (phenotype)

The reappearance of white-flowered plants in the
F2 generation indicated that the heritable factor
for the white trait was not diluted or blended
by coexisting with the purple-flower factor in F1
hybrids.
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Law of segregation-the two alleles for a
character are packaged into separate gametes
This segregation of alleles corresponds to the
distribution of homologous chromosomes to
different gametes in meiosis.
packaged into separate gametes
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USING THE Law of segregation..

• A Punnett square predicts the results of a
  genetic cross between individuals of known
  genotype.
• Two heterozygotes -
• 31 ratio of dominant recessive phenotypes
• 131 genotypes

• PRACTICE
• DRAGON Genetics
• 1 2
• Genetics Practice 8,17

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• When crossing two pure breeding plants, Mendel
  found similar 3 to 1 ratios among F2 offspring
  when he conducted crosses for six other
  characters, each represented by two different
  varieties.

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• Predicting the genotype of an organism with the
  dominant phenotype
• The organism must have at least one dominant
  allele, but it could be homozygous dominant or
  heterozygous.

whats the genotype?????
A testcross, breeding a homozygous recessive
with dominant phenotype, but unknown geneotype,
can determine the identity of the unknown allele.
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The law of independent assortment- each pair of
alleles segregates into gametes independently

• Alleles that are not on the same chromosome
• Ex. The alleles for height segregate
  independently from the alleles of a gene for
  color.
• AS long as the genes are on separate chromosomes,
  the separation during meiosis is RANDOM.

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The law of independent assortment- each pair of
alleles segregates into gametes independently
-During meiosis, the chromosomes line up randomly
during metaphase II. -So, depending on how they
line, this determines the alleles in each gamete.
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The law of independent assortment- each pair of
alleles segregates into gametes independently

• Mendels experiments that followed the
  inheritance of flower color or other characters
  focused on only a single character via monohybrid
  crosses.
• He conducted other experiments in which he
  followed the inheritance of two different
  characters, a dihybrid cross.

animation
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• If no independent assortment
• The F2 offspring (in dihybrid)
  would only produce two phenotypes
  in a 31 ratio, just like a monohybrid cross.
• This was not consistentwith Mendels results.

animation
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• Mendel crossed true-breeding plants that had
  yellow, round seeds (YYRR) with true-breeding
  plants that has green, wrinkled seeds (yyrr).
• When sperm with four classes of alleles and ova
  with four classes of alleles combined, there
  would be 16 equally probable waysin which the
  alleles can combine in the F2 generation.

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• These combinations produce four distinct
  phenotypes in a 9331 ratio.
• This was consistent with Mendels results.

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Black-BBrown-bLong hair-SShort-s

• Cross two purebred guinea pigs. Brown-long
  hair x Black-short hair
• Give phenotype and genotype ratios.

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Mendelian inheritance reflects rules of
probability

• Mendels laws reflect the laws of probability.
• The probability scale ranged from zero (an event
  with no chance of occurring) to one (an event
  that is certain to occur).
• The probability of tossing heads with a normal
  coin is ½.
• The probability of rolling a 3 with a six-sided
  die is 1/6, and the probability of rolling any
  other number is 1 - 1/6 5/6.

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• When tossing a coin, the outcome of one toss has
  no impact on the outcome of the next toss.
• Each toss is an independent event, just like the
  distribution of alleles into gametes.
• Like a coin toss, each ovumfrom a heterozygous
  parent has a ½ chance of carrying the dominant
  allele and a ½chance of carrying the recessive
  allele.
• The same odds apply to the sperm.

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• Rule of multiplication to determine the chance
  that two or more independent events will occur
  together in some specific combination.
• Compute the probability of each independent
  event.
• Multiply the individual probabilities.
• The probability that two coins tossed at the same
  time will land heads up is
• ½ x ½ ¼.
• Similarly, the probability that two heterozygous
  pea plants (Pp) will produce a white-flowered
  offspring (pp) depends on an ovum with a white
  allele mating with a sperm with a white allele.
• ½ x ½ ¼.

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• Rule of multiplication also applies to dihybrid
  crosses.
• For a heterozygous parent (YyRr) the probability
  of producing a YR gamete is ½ x ½ ¼.
• We can use this to predict the probability of a
  particular F2 genotype without constructing a
  16-part Punnett square.

• The probability that an F2 plant will have a YYRR
  genotype from heterozygous parents is
• 1/16 (¼ chance for a YR ovum and ¼ chance for a
  YR sperm).

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• Examples
• An organism had three independently assorting
  traits AaBbCc. What fraction of its gamete will
  contain ABC?
• 1/8
• What about an organism with AABcCc? What fraction
  of its gamete will contain ABC?
• 1/4

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Rule of addition When more than one arrangement
of the events producing the specified outcome is
possible, the individual probabilities are added.

• determine the probability of an offspring having
  two recessive phenotypes for at least two of
  three traits resulting from a trihybrid cross
  between pea plants that are PpYyRr and Ppyyrr.
• There are five possible genotypes that fulfill
  this condition ppyyRr, ppYyrr, Ppyyrr, PPyyrr,
  and ppyyrr.
• Determine probability of each and then add
  together.

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• For ppYyrr 1/4 1/2 1/2 1/16.
• For Ppyyrr 1/2 1/2 1/2 1/8 or 2/16.
• For PPyyrr 1/4 1/2 1/2 1/16.
• For ppyyrr 1/4 1/2 1/2 1/16.
• Therefore, the chance that a given offspring will
  have at least two recessive traits is 1/16 2/16
  1/16 1/16 6/16.

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• Website

REVIEW
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THE CHROMOSOMAL BASIS OF INHERITANCE
1.Morgan traced a gene to a specific
chromosome 2. Linked genes tend to be inherited
together because they are located on the same
chromosome 3. Independent assortment of
chromosomes and crossing over produce genetic
recombinants 4. Geneticists use recombination
data to map a chromosomes genetic loci
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Introduction

• It was not until 1900 that biology finally caught
  up with Gregor Mendel.
• Mendels hereditary factors are the genes located
  on chromosomes.

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Mendelian inheritance has its physical basis in
the behavior of chromosomes during sexual life
cycles

• Around 1900, cytologists and geneticists began to
  see parallels between the behavior of chromosomes
  and the behavior of Mendels factors.

Around 1902, Walter Sutton, Theodor Boveri, and
others noted these parallels and a chromosome
theory of inheritance began to take form.
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• CHROMOSOMAL THEORY OF INHERITANCE
• Chromosomes are carriers of traits and each
  chromosome could carry the genes for MANY traits.
• Alternate forms or ALLELES of a gene are located
  on matched pairs of chromosomes.
• When chromosome pairs separate in meiosis, each
  chromosome carries its set of alleles to a
  gamete.
• Genes of the same chromosome move together
  Genes on different chromosomes assort
  independently.

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Morgan traced a gene to a specific chromosome

• He was the first to associate
  a specific
  gene with a specific
  chromosome.
• Worked with Drosophila
  melanogaster
• Prolific breeders have a
  generation time of two
  weeks.
• 3 pairs of autosomes and a pair of
  sex chromosomes

• Produces about 100 offspring per egg lay good
  statistics!
• Easy/inexpensive to raise
• Chromosomes are VERY large and easy to see and
  locate
• Sexes are easily distinguished
• --female is larger
• --shapes of abdomen identify sexes at a glance

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• Morgan spent a year looking for variant
  individuals among the flies he was breeding.
• He discovered a single male fly with white eyes
  instead of the usual red.
• The normal phenotype is the wild type.
• Alternative traits mutant phenotypes.

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Morgans Experiments Findings

• When Morgan crossed his white-eyed male with a
  red-eyed female, all the F1 offspring had red
  eyes,
• The red allele appeared dominant to the white
  allele.
• Crosses between the F1 offspring produced the
  classic 31 phenotypic ratio in the F2 offspring.
• Surprisingly, the white-eyed trait appeared only
  in males.
• All the females and half the males had red eyes.
• Morgan concluded that a flys eye color was
  linked to its sex.

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• Morgan deduced that the gene with the white-eyed
  mutation is on the X chromosome, a sex-linked
  gene.

• Females (XX) may have two red-eyed alleles and
  have red eyes or may be heterozygous and have red
  eyes.
• Males (XY) have only a single allele and will be
  red eyed if they have a red-eyed allele or
  white-eyed if they have a white-eyed allele.

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Sex-linked
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Sex-linked Genes
Sex Chromosomes
1.Sex-linked genes have unique patterns of
inheritance 2.The chromosomal basis of sex varies
with the organism
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Sex-linked Genes

• In addition to their role in determining sex, the
  sex chromosomes, especially the X chromosome,
  have genes for many characters unrelated to sex.
• Males are hemizygous for the X chromosome (XY)

Karyotype
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Sex-linked Genes

• If a sex-linked trait is due to a recessive
  allele, a female will have this phenotype only if
  homozygous.
• Heterozygous females will be carriers.
• Because males have only one X chromosome
  (hemizygous), any male receiving the recessive
  allele from his mother will express the trait.
• The chance of a female inheriting a double dose
  of the mutant allele is much less than the chance
  of a male inheriting a single dose.
• Therefore, males are far more likely to inherit
  sex-linked recessive disorders than are females.

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Sex-linked Genes

• Hemophilia Colorblindness are all on
  the X-chromosome
• Several serious human disorders are sex-linked.
• Duchenne muscular dystrophy affects one in 3,500
  males born in the United States.
• Affected individuals rarely live past their early
  20s.

• due to the absence of an X-linked gene for a key
  muscle protein, called dystrophin.
• a progressive weakening of the muscles and a loss
  of coordination.

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Sex-linked Genes-Barr body

• Although female mammals inherit two X
  chromosomes, only one X chromosome is active.
• Therefore, males and females have the same
  effective dose (one copy ) of genes on the X
  chromosome.
• During female development, one X chromosome per
  cell condenses into a compact object, a Barr
  body.
• This inactivates most of its genes.
• Barr body occurs randomly and independently
• If a female is heterozygous for a sex-linked
  trait, approximately half her cells will express
  one allele and the other half will express the
  other allele.
• The condensed Barr body chromosome is reactivated
  in ovarian cells that produce ova.
• In humans, this mosaic pattern is evident in
  women who are heterozygous for a X-linked
  mutation that prevents the development of sweat
  glands.
• Hypohidrotic ectodermal dysplasia
• A heterozygous woman will have patches of normal
  skin and skin patches lacking sweat glands.

Animation
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• Cool example the orange and black pattern on
  tortoiseshell cats is due to patches of cells
  expressing an orange allele while others have a
  nonorange allele.

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• In human and other mammals, there are two
  varieties of sex chromosomes, X and Y.
• XX female. XY male.

• This X-Y system of mammals is not the only
  chromosomal mechanism of determining sex.
• Other options include
• X-0 system (Grasshoppers, roaches, and other
  insects)
• Z-W system (Birds, insects like butterflies,
  frogs and some species of fish)
• the haploid-diploid system.

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• In humans, the anatomical signs of sex first
  appear when the embryo is about two months old.

• In individuals with the SRY gene (sex-determining
  region of the Y chromosome), the generic
  embryonic gonads are modified into testes.
• In individuals lacking the SRY gene, the generic
  embryonic gonads develop into ovaries.

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Multiple Alleles
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Multiple Alleles - genes that exist in more two
allelic forms
Multiple Alleles
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• Practice Problems

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Linked Genes
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Linked genes tend to be inherited together
because they are located on the same chromosome

• Chromosome have 100s or
  1000s of genes.
• Genes located on the same chromosome
  are called linked genes
• tend to be inherited together
  because the chromosome is
  passed along as a unit.
• Results of crosses with linked genes deviate from
  those expected according to independent
  assortment.

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• Morgan observed this linkage (and its deviations)
  when he followed the inheritance of characters
  for body color and wing size.
• The wild-type body color is gray (b) and the
  mutant black (b).
• The wild-type wing size is normal (vg) and the
  mutant has vestigial wings (vg).
• Morgan crossed F1 heterozygous females (bbvgvg)
  with homozygous recessive males (bbvgvg).
• (according to Mendelian genetics, what genotypes
  should he get in the F2 generation?)

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• According to independent assortment, this should
  produce 4 phenotypes in a 1111 ratio.
• THAT NOT WHAT HE OBSERVED
• He observed a large number of wild-type
  (gray-normal) and double-mutant (black-vestigial)
  just like the parents.
• Fewer recombinations than expected!!!!!

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Morgans conclusions

• He reasoned that body color and wing shape are
  usually inherited together because their genes
  are on the same chromosome (Linked).
• The other two phenotypes (gray-vestigial and
  black-normal) were fewer than expected from
  independent assortment (and totally unexpected
  from dependent assortment).
• These new phenotypic variations must be the
  result of crossing over.

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• The results of Morgans testcross for body color
  and wing shape did not conform to either
  independent assortment or complete linkage.
• Under independent assortment the testcross should
  produce a 1111 phenotypic ratio.
• If completely linked, we should expect to see a
  1100 ratio with only parental phenotypes among
  offspring.
• Most of the offspring had parental phenotypes,
  suggesting linkage between the genes.
• However, 17 of the flies were recombinants,
  suggesting incomplete linkage.

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• Morgan proposed that some mechanism occasionally
  exchanged segments between homologous
  chromosomes.
• This switched alleles between homologous
  chromosomes.
• The actual mechanism, crossing over during
  prophase I, results in the production of more
  types of gametes than one would predict by
  Mendelian rules alone.

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• Crossing over accounts for the recombinant
  phenotypes in Morgans testcross.

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Geneticists can use recombination data to map a
chromosomes genetic loci

• One of Morgans students, Alfred Sturtevant, used
  crossing over of linked genes to develop a method
  for constructing a genetic map.
• This map is an ordered list of the genetic loci
  along a particular chromosome.

Alfred Sturtevant
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• Sturtevant hypothesized that the frequency of
  recombinant offspring reflected the distances
  between genes on a chromosome.
• The farther apart two genes are, the higher the
  probability that a crossover will occur between
  them and therefore a higher recombination
  frequency.
• The greater the distance between two
  genes,
  the more points between them
  where crossing
  over can occur.
• Sturtevant used recombination frequencies from
  fruit fly crosses to map the relative position of
  genes along chromosomes, a linkage map.

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• Sturtevant used the testcross design to map the
  relative position of three fruit fly genes, body
  color (b), wing size (vg), and eye color (cn).
• The recombination frequency between cn and b is
  9.
• The recombination frequency between cn and vg is
  9.5.
• The recombination frequency between b and vg is
  17.
• The only possible arrangement of these three
  genes places the eye color gene between the
  other two.
• Expressed the distance
  between genes, the
  
  recombination frequency,
  as map units.
• One map unit (sometimes called a centimorgan) is
  equivalent to a 1 recombination frequency.

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A couple of points..

• Some genes on a chromosome are so far apart that
  a crossover between them is virtually certain.
• In this case, the frequency of recombination
  reaches is its maximum value of 50 and the genes
  act as if found on separate chromosomes and are
  inherited independently.
• In fact, several genes studies by Mendel are
  located on the same chromosome.
• For example, seed color and flower color are far
  enough apart that linkage is not observed.
• Plant height and pod shape should show linkage,
  but Mendel never reported results of this cross.

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A couple of points..

• Genes located far apart on a chromosome are
  mapped by adding the recombination frequencies
  between the distant genes and intervening genes.
• Sturtevant and his colleagues were able to map
  the linear positions of genes in Drosophila
  into four groups, one for each chromosome.

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Your turn to do some MAPPING

• Anaylsis
• If the two genes showed independent assortment,
  we would hypothesize a 1111 ratio of
  phenotypes from the testcross done.
• Instead, most resemble the phenotypes of the two
  original parents (the normal round eyes and no
  tooth, and the double mutant vertical eyes and
  tooth). We must conclude that the genes do not
  assort independently.
• How many map units between these 2 linked genes?

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Solution
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Another practice problem

• Determine the sequence of genes along a
  chromosome based on the following recombination
  frequencies
• A-B, 8 map units
• A-C, 28 map units
• A-D, 25 map units
• B-C , 20 map units
• B-D, 33 map units.

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Steps for solving
Solution

• Choose the greatest map distance (in this case
  33) and place the genes involved at opposite ends
  of a line representing a portion of the
  chromosome in question
• Now choose a gene combination with either B or D
  in it. For example A-D 25 map units
• Since A-B is only 8 map units, A must be
  in the middle
• Now choose on that has A in it
• You already have A-D and A-B, so all that is left
  is A-C, but where does it gowhich side?
• Since the distance from A to B is about 8 and the
  distance from C to B is less than the distance
  from A to B the C-gene must be to the left of the
  B-gene.

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Practice

• A phenotypic wild-type fruit fly (heterozygous
  for gray body color and red eyes) was mated with
  a double mutant black fruit fly with purple eyes.
  
• The offspring were as follows wild-type, 721
  black-purple, 751 gray-purple, 49 black-red,
  45.
• (a) What is the recombination frequency between
  these genes for body color and eye color?
• (b) Are these genes on the same chromosome? If
  so, how far apart are they?

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Solution

• Genotypes
• b gray body
• b black body
• pr red eyes
• pr purple eyes

Total flies 1566 (a) The percent recombination
is therefore 6
6
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1. Alterations of chromosome number or structure
cause some genetic disorders
Nondisjunction
Aneuploidy
Polyploidy
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Nondisjunction

• Nondisjunction occurs when problems with the
  meiotic spindle cause errors in daughter cells.
• This may occur if tetrad chromosomes do not
  separate properly during meiosis I.
• Alternatively, sister chromatids may fail to
  separate during meiosis II.

Consequence- some gametes receive two of the same
type of chromosome and another gamete receives no
copy.
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Aneuploidy

• Aneuploidy Abnormal chromosome .
• Trisomic cells have 3 copies of a particular
  chromosome type
• Down syndrome, Klinefelters
• Monosomic cells have only 1 copy of a particular
  chromosome type.
• Turner syndrome

condition in which a female does not have the
usual pair of two X chromosomes

• Can occur during failures of the mitotic spindle.

Aneuploidy occurs during cell division when the
chromosomes don't separate properly
(nondisjunction) between the two cells.
Chromosome abnormalities occur in 1 of 160 live
births, the most common being extra chromosomes
21 (Down syndrome), 18 (Edwards syndrome) and 13
(Patau syndrome).
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Aneuploidy-trisomy

• Down syndrome, is due to three copies of
  chromosome 21.
• Caused by nondisjunction
• It affects one in 700 children born in the United
  States.
• Although chromosome 21 is the smallest human
  chromosome, it severely alters an individuals
  phenotype in specific ways.

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Down Syndrome
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Klinefelter Syndrome
Aneuploidy-trisomy

• Affects only males.
• Caused by nondisjunction.
• Males who have Klinefelter
  syndrome have an extra X
  chromosome (XXY), giving them a total
  of 47 instead
  of the normal 46 chromosomes

• Develop as males with subtle characteristics that
  become apparent during puberty. They are often
  tall and usually don't develop secondary sex
  characteristics, such as facial hair or underarm
  and pubic hair. The extra X chromosome primarily
  affects the testes, which produce sperm and the
  male hormone testosterone.
• At puberty, men with this syndrome often develop
  more breast tissue than normal, have a less
  muscular body, and grow very little facial or
  body hair. Most are sterile because they cannot
  produce sperm. Learning disabilities are also a
  common problem for them.
• Hormone replacement Teenagers are typically
  given testosterone injections to replace the
  hormone that would normally be produced by the
  testes.

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Polyploidy

• More than two complete sets of chromosomes.
• This may occur when a normal gamete fertilizes
  another gamete in which there has been
  nondisjunction of all its chromosomes.
• The resulting zygote would be triploid ( n).

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• Polyploidy is relatively common among plants and
  much less common among animals.
• Both fishes and amphibians have polyploid
  species.
• Recently, researchers in Chile have identified
  a new rodent species that may be the product
  of polyploidy.

Triploid crops banana, apple, grass carp, ginger
Tetraploid crops durum or macaroni wheat,
maize, cotton, potato, cabbage, leek, tobacco,
peanut, Pelargonium Hexaploid crops
chrysanthemum, bread wheat, triticale, oat
Octaploid crops strawberry, dahlia, pansies,
sugar cane
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Charts that show relationships within a family
Pedigree
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• How many boys? __________________
• How many Girls? __________________
• How many generations? _______________
• How many with the disorder? ____________
• How many marriages are shown? ____________

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12
3
4
6
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1. How many generations?
2. How many carriers?
3. How many affected males?
4. How many affected females?
5. Autosomal or sex-linked?

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Autosomal-Dominant
What can you tell by the pedigree? Dominant or
recessive? Autosomal or sex-linked?
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SEX-LINKED
What can you tell by the pedigree? Dominant or
recessive? Autosomal or sex-linked?
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SEX-LINKED
What can you tell by the pedigree? Dominant or
recessive? Autosomal or sex-linked?
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Autosomal -Dominant
Dominant or recessive? Autosomal or sex-linked?
NO carriers when Dominant.
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Autosomal -Recessive
Carriers when recessive.
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Practice

• 1) How many unique gametes could be produced
  through independent assortment by an individual
  with the genotype AaBbCCDdEE? AaBbCcDDEe?
• 2) Genes A, B, and C are located on the same
  chromosome. Testcrosses show that the
  recombination frequency between A and B is 28
  and between A and C is 12. Can you determine
  the linear order of these genes?
• 3) Study guide p.116 Genetics Problmes 1,2,3
• 6) Study Guide p117, Questions 7
• 7) Study Guide p118 question 16, 17,18
• 8) Book page 292 8
• 9) Book page 292 9

97
Video Clips to Watch
Cassiopeia Poject Genetics Disorders http//www.p
bs.org/wgbh/nova/genome/program_adv.html

• http//highered.mcgraw-hill.com/sites/0072437316/s
  tudent_view0/chapter16/animations.html