A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below. Assume A and B are dominant alleles.If this individual were crossed to an individual of genotype Aa Bb, what is the probability of a female offspring with the two dominant traits given by alleles A and B?

Question

A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below.  Assume A and B are dominant alleles.If this individual were crossed to an individual of genotype Aa Bb, what is the probability of a female offspring with the two dominant traits given by alleles A and B?

Quizplus · Accepted Answer

Since the individual with the ZZ-ZW sex determination system is diploid, it carries two copies of each autosome and one sex chromosome from each parent. Let's label the individual with the ZZ-ZW sex chromosomes as ZW and the individual with genotype Aa Bb as AB.

The possible gametes produced by the ZW individual are Z and W. The possible gametes produced by the AB individual are AB, Ab, aB, and ab.

To determine the probability of a female offspring with the two dominant traits given by alleles A and B, we need to consider the different possible combinations of gametes that can lead to this outcome:

- ZW x AB: 
There are four possible zygotes that can result from this cross: ZA, ZB, WA, and WB. Only the ZBWB zygote will result in a female offspring with two dominant traits.
The probability of producing the ZBWB zygote is 1/4 x 1/4 = 1/16.
However, we need to multiply this probability by two, since there are two possible orders in which the Z and W chromosomes can be inherited (ZW from the mother and AB from the father, or AB from the father and ZW from the mother). Therefore, the overall probability of producing a female offspring with the two dominant traits given by alleles A and B is 2 x 1/16 = 1/8.
- ZW x Ab: 
This cross will not produce a female offspring with two dominant traits, since the Ab gamete does not carry the dominant B allele.
- ZW x aB: 
This cross will not produce a female offspring with two dominant traits, since the aB gamete does not carry the dominant A allele.
- ZW x ab: 
This cross will not produce a female offspring with two dominant traits, since the ab gamete does not carry the dominant A or B alleles.

Therefore, the probability of a female offspring with the two dominant traits given by alleles A and B is 1/8 (Option D).

A Eukaryotic Diploid Cell from an Organism with the ZZ-ZW