Question

5. The eye color gene in fruitflies is located on the X chromosome. The dominant wild-type X^+ allele produces red eyes, while the recessive XW allele produces white eyes. In addition, sex is determined in fruitflies by the ratio of the number of X chromosomes to number of sets of autosomes.

Imagine that a pure-breeding white-eyed female with the genotype X^W X^W Y AA mates with a pure-breeding red-eyed male who has the genotype X^+ Y AA. Imagine that nondisjunction occurs between the females’ X chromosomes during 12% of her meioses. Imagine also that they produce 100 offspring.

What number (not percentages—give me actual numbers out of 100 total offspring) of F1 generation offspring do you expect to have the different possible genotypes and phenotypes this mating pair can produce in their F1 offspring? When you give the phenotypes, give me sex and eye color. If two different genotypes produce the same sex/eye color phenotypes, list the two genotype/phenotype combinations separately. Also, remember that a fruitfly can’t live without an X chromosome. If an individual does not have an X, it dies very early--without its sex being determined (call the phenotype “lethal, no sex”).

Please give an explanation. This is all of the same question, there is no more info given.

Answer 1

Here in the quistion it is said that non disjunction occurs between female chromosome, thats why the given female drosophila have the genotype of ,(normally female genotype is (for white eyed))

So here we want to perform a cross between (Female) and (male), where + (allele) dominant over w(allele).

So the gametes produced by females contains or and the gametes produced by male have or .

So the progenies formed are , , , and (If no nondisjunction happened in F1).

here red eyed female,

is white eyed male,

is red eyed male,

sex not specified.

so out of 4 offspring red eyed female : white eyed male : red eyed male : sex not specified=1:1:1:1

so in 100 progeny it should be in 25:25:25:25.

[ if nondisjunction happened in X chromosome in female parent, then the gametes formed from the female are

and and the possibel proegenies are , ,and