2. (10 points) A father has dimples, the mother does not have dimples, and one o

ID: 277020 • Letter: 2

Question

2. (10 points) A father has dimples, the mother does not have dimples, and one of their three children have dimples but the other two do not. Dimples (D) are dominant over no dimples (d). Give the probable genotypes of all five persons concerned.

3. (10 pts)

Explain the process you would use to tell if an F2 seed that appeared to have the dominant phenotype was homozygous dominant or heterozygous.

4.(10 points) Both the husband and wife have normal vision. The wife gives birth to a color-blind daughter. What can you deduce about the girl’s parentage? Explain why.

Explanation / Answer

1. If dimple is dominant (D) over non dimple (d), which means DD or Dd both will be dominant form and dd will be recessive.

the genotype of father should be Dd and mother dd, as if father has the genotype DD, all the childrens will be Dd or having dimple. But as one of them has dimple and other two do not , father can not be DD.

Dd X dd

thus the children who has dimple has the genotype = Dd

other two children who do not have the dimple will have the genotype= dd

2. the process is called testcross. In testcross the recessive individual is crossed with homozygous or heterozygous individual and based on the phenotype we can conclude whether the dominant individual is homozygous or heterozygous.

for eg a purple flower can be PP or Pp whereas a white flower has the recessive genotype pp

thus if a puprle flower is PP , then when crossed with pp, all flowers will be purple in phenotype.

PP X pp

on the other hand if the purple dominant flower is heterozygous Pp , then when crossed with recessive white flower pp, then 50% of the offspring flower will be purple (Pp) and 50% of the flower will be white (pp)

Pp X pp

3. colour blindness is X linked recessive allele. If a man has normal vision, then he will ba XY . On the other hand if the daughter is colour blind then she will have both X chromosome with colour blind gene . The genotype of daughter will be XaXa. But as the mother has normal vision, she can be carrier having one normal X chromosome and other X chromosome will have Xa.

depending on the genotype status of their parent the cross will be

XY X XaXa

in this scenario, the daughters will always have normal vision and will be carrier for colour blindness. Thus if the female gave birth to a colour blind daughter, the father will be someone else, who is colourblind.

XaX

normal vision

Xa X

normal vision

XaY

affected male

XaY

affected male

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2. (10 points) A father has dimples, the mother does not have dimples, and one o

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