Question

You now know thatinheritance of eye color in fruit flies is sex-linked: The gene encoding eye color is located on the X chromosome, and there is no corresponding gene on the Ychromosome.
How would the inheritance pattern differ if the gene for eye color were instead located on an autosome (a non-sex chromosome)? Recall that for autosomes, bothchromosomes of a homologous pair carry the same genes in the same locations.
Suppose that a geneticist crossed a large number of white-eyed females with red-eyed males.
Consider two separate cases:
Case 1: Eye color exhibits sex-linked inheritance.
Case 2: Eye color exhibits autosomal (non-sex-linked) inheritance. (Note: In this case, assume that the red-eyed males are homozygous.)
For each case, predict how many of the male and female offspring would have red eyes and white eyes.
Drag the correct numbers on the left to complete the sentences on the right. Numbers can be used once, more than once, or not at all.

1. If there were 100 female offspring, _______would have red eyes and ______ would have white eyes.

2. If there were 100 male offspring, _______would have red eyes and ______would have white eyes.

3. If there were100 female offspring, ______would have red eyes and _____ would have white eyes.

4. If there were 100 male offspring, _____ would have red eyes and _____ would have white eyes.

Label- 0, 25, 50, 75, 100

Answer 1

We know the phenotype of the females, but we actually do not know the genotype. Note that I have given two sets of answers. Try the first setfirst. Don't mix the answers though.

Assuming they want us to assume heterozygous for the females:

1. If there were 100 female offspring, ___50____would have red eyes and __50____ would have white eyes.

2. If there were 100 male offspring, ___50____would have red eyes and __50____would have white eyes.

3. If there were100 female offspring, __50____would have red eyes and __50___ would have white eyes.

4. If there were 100 male offspring, _50____ would have red eyes and __50___ would have white eyes.

Starting over and assuming they want us to assume homozygous for the females:

1. If there were 100 female offspring, ___0____would have red eyes and __100____ would have white eyes.

2. If there were 100 male offspring, ___0____would have red eyes and __100____would have white eyes.

3. If there were100 female offspring, __0____would have red eyes and __100___ would have white eyes.

4. If there were 100 male offspring, _0____ would have red eyes and __100___ would have white eyes.

Answer 2

Case 1
1)100,0
2)0,100

Case 2
White is recessive
A a
A AA Aa
a Aa aa
3)0,100 (since female white eyed only recessive homozygous present)
4)75,25 (Normal case)
My answers are based on this explanation
Morgan performed the reciprocalcross i.e.
mating of white-eyed female with red-eyed male,
He found different results. Although, the F1 progeny were 50% female and 50% male as before but all the female flies were red-eyed and all the males werewhite-eyed. In F2 50% female and 50% male and 50% red eyed and 50% white eyed as well.
Here again the male received the X chromosome carrying the wild type allele from their mother.