Question

2. In fruit flies, red eye color (X) is dominant over white eye color (X) and the trait is sex-linked. Cross a

red-eyed male and a heterozygous red-eyed female.
Red eye
a. Parent Phenotypesred
b. Parent Genotypes E
Key: X
Ye
a. Parent Phenotypes
b. Parent Genotypes
X'= White ole
X
X XEXE
c. Genotype fractions of offspring
X
3. In humans, color blindness (X) is recessive to normal vision (XB) and is sex-linked. Show what the Punnett
square would look like for a cross between a color blind father and a mother that is a carrier (heterozygous) for
the condition.
Key: X"=
d.Phenotype fractions of offspring
X
c. Genotype fractions of offspring
d.Phenotype fractions of offspring

Answer 1

a. Parent Phenotypes: Red eye (male), Red-eye (female)

b. Parent Genotypes:
`X^E`Y (male),
`X^E`X (female)

c. Genotype fractions of offspring:

- 50%
`X^E`Y (red-eyed males)

- 50%
`X^E`X (red-eyed females)

d. Phenotype fractions of offspring:

- 50% Red-eyed males

- 50% Red-eyed females

In humans, color blindness (
`X^c`) is recessive to normal vision (
`X^B`) and is sex-linked.

Punnett square for a cross between a color-blind father (
`X^c`Y) and a carrier mother (
`X^BX^c`):

markdown

`X^c` Y

`X^B | X^BX^c X^BY`

`X^B | X^BX^c X^BY`

c. Genotype fractions of offspring:

- 50%
`X^BX^c` (carrier females)

- 50%
`X^BY` (normal vision males)

d. Phenotype fractions of offspring:

- 50% Carrier females

- 50% Normal vision males

The Punnett square illustrates the possible genotypes and phenotypes of the offspring based on the parents' genotypes. The genotype fractions show the proportion of each genotype among the offspring, while the phenotype fractions indicate the proportion of each phenotype.

For more such answers on Punnett square