Across in drosophila involved the recessive, x linked genes yellow (y), white (w), and cut (ct). a yellow-bodied, white-eyed female with normal wings was crossed to a male whose eyes and body were normal but whose wings were cut. the f1 females were wild type for all three traits while the males expressed the yellow body and white eye traits. the cross was carried to the f2 progeny and only male offspring were evaluated. on the basis of the data shown here, a genetic map was constructed. what are the genotypes of the f1 females and males? how did you decide?

x-linked genes are genes associated with the sexual X chromosomes. So they are only inherited from the mother/female side. Males express the phenotype defined by the allele received from the mother.

Available data:

                                                          →   allele y recessive →  yellow

                                                         →   allele g recessive →  white

                                                               →   allele ct recessive →  cut

Let us first analyze genotype and phenotypes.

For a better representation, I will stablish symbols representing the alelles

GENOTYPE                                PHENOTYPE        

Xᵃ⁺Xᵃ⁺  -   Xᵃ⁺Xᵃ⁻  -  Xᵃ⁺Y         Normal body color

Xᵃ⁻Xᵃ⁻  -   Xᵃ⁻Y                          Yellow body color

Xᵇ⁺Xᵇ⁺  -   Xᵇ⁺Xᵇ⁻  -  Xᵇ⁺Y         Normal eye color

Xᵇ⁻Xᵇ⁻  -  Xᵇ⁻Y                           White eye color

Xⁿ⁺Xⁿ⁺  -  Xⁿ⁺Xⁿ⁻  -  Xⁿ⁺Y          Normal wings

Xⁿ⁻Xⁿ⁻   -  Xⁿ⁻Y                          Cut wings                  

Now let us represent the cross

Cross) Male x female

There are two options of crosses according to the female genotype

Parentals) Xᵃ⁻ ᵇ⁻ ⁿ⁺ Xᵃ⁻ ᵇ⁻ ⁿ⁺    x     Xᵃ⁺ ᵇ⁺ ⁿ⁻ Y

                 Xᵃ⁻ ᵇ⁻ ⁿ⁺ Xᵃ⁻ ᵇ⁻ ⁿ⁻    x     Xᵃ⁺ ᵇ⁺ ⁿ⁻ Y

F1)

According to the statement of the problem,

⇒ the females in the F1 are wild type for all the traits.

Because F1 females express the wild type phenotype for wings shape, we can assume that they inherited the dominant allele from the mother.

So females must be heter0zyg0us all the traits ⇒ Xᵃ⁺ ᵇ⁺ ⁿ⁺ Xᵃ⁻ ᵇ⁻ ⁿ⁻

⇒ the males in the F1 have yellow body and white eyes.

Male inherited from the mother the recessive alleles for eye color and body color. It could inherit a dominant allele for wings shape, or a recessive one.

So the male genotype can be either   Xᵃ⁻ ᵇ⁻ ⁿ⁺ Y    or   Xᵃ⁻ ᵇ⁻ ⁿ⁻ Y

Considering that the statement only specified the recessive phenotype for body and eye color, we could assume that the male expresses the dominant phenotype for wings shape   ⇒   Xᵃ⁻ ᵇ⁻ ⁿ⁺ Y

F1 Genotypes

                                                         color and wild type for wings shape

Related link: link

the answer is definitely a