Cross a homozygous dominant green plant with a heterozygous green plant. What are the genotypic and phenotypic ratios.

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Cross a homozygous dominant green plant with a
heterozygous green plant. What are the genotypic
and phenotypic ratios.

• Agenda for Monday April 11th
• 1. Complex patterns of inheritance
• Incomplete and Co-dominance

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Incomplete Dominance

• Complete dominance a heterozygous individuals
  phenotype will show the dominant trait
• When red snapdragons (RR) were crossed with white
  snapdragons (rr) offspring were pink (Rr)

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Incomplete Dominance

• one allele for a trait is not completely dominant
  over the other allele
• Combined phenotype (blended)

R allele for red flowers W allele for white
flowers red x white ---gt pink RR x WW ---gt 100
RW
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Co-dominance

• In COdominance, the "recessive" "dominant"
  traits appear together in the phenotype of hybrid
  (heterozygous) organisms

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Practice

• Set up genotypes for the phenotypes listed in
  each set. Remember that the "medium" trait is
  always heterozygous.
• a) Birds can be blue, white, or white with
  blue-tipped feathers.
• b) Flowers can be white, pink, or red.
• c) A Hoo can have curly hair, spiked hair, or a
  mix of both curly and spiked.
• D) A Sneech can be tall, medium, or short.

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• 1. Write the genotypes for the pictured
  phenotypes
• 2. Show the cross between a star-eyed and a
  circle eyed. What are the phenotypes of the
  offspring? What are the genotypes?

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• 3. Show the cross between a circle-star eyed, and
  a circle eyed.How many of the offspring are
  circle-eyed? How many of the offspring are
  circle-star eyed?
• Write the genotypic and phenotypic ratios.
• 4. Show the cross between two circle-star eyed.
  How many of the offspring are circle-eyed? How
  many of the offspring are circle-star eyed? How
  many are star eyed?

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Welcome

• In humans, straight hair (ss) and curly hair (cc)
  are co-dominant traits that result in hybrids
  that have wavy hair (sc). Cross a Straight hair
  female with a wavy haired male.
• What are the chances of having a curly haired
  child?
• What are the chances of having a straight hair
  child?
• What are the chances of having a wavy hair child?

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Agenda

• Quiz
• Sex Linked Traits

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Sex Determination

• Thomas Hunt Morgan studied fruit flies in the
  early 1900s

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Sex Determination

• Observed that one pair of chromosomes was
  different between males and females
• Large one named X chromosome
• Smaller one named Y chromosome
• XX female XY male

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XY
XX
X
Y
X
X
X
X
XX Female
XX Female
X
XY Male
XY Male
Y
50 Female 50 Male
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Sex Linkage

• Sex Linkage the presence of a gene on a sex
  chromosome (X or Y)

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Sex Linkage

• X-linked genes genes found on the X chromosome
• X chromosome carries more genes
• Y-linked genes genes found on the Y chromosome

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Fruit Fly Eye Color

• Fruit flies normally have red eyes
• A few males have white eyes
• Red is dominant
• white is recessive

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Welcome to Class

• What is sex linkage?

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Agenda

• Finish sex linked traits notes
• worksheet

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Morgans Fruit Fly Experiments

• Red-eyed female (XRXR) x White-eyed male (XrY)

XR
XR
XRXr
XRXr
RESULTS F1 generation all red-eyed
Xr
XRY
XRY
Y
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Morgans Fruit Fly Experiments

• Red-eyed female (XRXr) x Red-eyed male (XRY)

XR
Xr
RESULTS F2 generation 3 red-eyed and 1
white-eyed all white-eyed where maleswhy?
XRXR
XRXr
XR
XRY
XrY
Y
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Morgans Conclusions

• Gene for eye color is carried on the X chromosome
  eye color is an X-linked trait
• Y chromosome does not carry a gene for eye color
• Red-eyed XRXR, XRXr , XRY
• White-eyed XrXr, XrY

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• In humans colorblindness (b) is an example of a
  sex-linked recessive trait. A male with
  colorblindness marries a female who is not
  colorblind but carries the (b) allele.
• Using a Punnett square, determine the genotypic
  and phenotypic probabilities for their potential
  offspring.

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• In fruit flies red eye color (R) is dominant to
  white eyes (r). In a cross between two flies, 50
  of the male and 50 of the female offspring had
  red eyes. The other half of the males and females
  had white eyes.
• What are the phenotype, and all possible
  genotypes, of the offspring?

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Welcome to Class

• In fruit flies red eye color (R) is dominant to
  white eyes (r). Cross a heterozygous female with
  a white eye male. What are the phenotypic and
  genotypic ratios?

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Agenda

• Review Sex linked traits
• Multiple Alleles

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Epistasis

• Epistasis when one allele hides another
• Labrador Coat Color
• 2 alleles
• Dominant allele E determines pigment
• ee will have no pigment
• Dominant allele B determines how dark the pigment
• EEbb or Eebb chocolate brown
• eebb, eeBb, or eeBB will be yellow because e
  masks effects of dominant B allele

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Multiple Alleles

• Multiple alleles traits that are determined by
  more than 2 alleles
• We have only 2 alleles (1 from mom, 1 from dad)
• Blood groups (ABO)
• O is recessive (i allele)

ALLELE IA IB i CODES FOR Type "A" Blood Type "B" Blood Type "O" Blood
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GENOTYPES IAIA IAi RESULTING PHENOTYPES Type A Type A
IBIB IBi Type B Type B
IAIB Type AB
ii Type O
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• More alleles means more combinations
• there are 6 different genotypes 4 different
  phenotypes for blood type
• Note 2 genotypes for both "A" "B" blood ---
  either homozygous (IAIA or IBIB) or heterozygous
  with one recessive allele for "O" (IAi or IBi).
• Note too that the only genotype for "O" blood is
  homozygous recessive (ii).
• And lastly, what's the deal with "AB" blood? 
  What is this an example of?  The "A" trait the
  "B" trait appear together in the phenotype.

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Problems

• A woman with Type O blood and a man who is Type
  AB have are expecting a child.  What are the
  possible blood types of the kid?
• What are the possible blood types of a child
  who's parents are both heterozygous for "B" blood
  type?

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One More

• What are the chances of a woman with Type AB and
  a man with Type A having a child with Type O?