Chapter 4 Questions 5. (0.5 points) Miniature wings in Drosophila melanogaster r

Question

Chapter 4 Questions 5. (0.5 points) Miniature wings in Drosophila melanogaster result from an X-linked a is recessive to long wings. Sepia eve color results from an autosomal allele that is recessive to red eyes. For the following cross, determine lele that the genotypes of the male and female parents. Phenotypes of Parents: Female Parents: Sepia Eyes, Long Wings Male Parents: Red Eyes, Long Wings Phenotypes of Offspring: Female Offspring: 1/2 Sepia Eyes, Long Wings 1/2 Red Eyes, Long Wings Male Offspring: 1/4 Sepia Eyes, Long Wings 1/4 Sepia Eyes, Miniature Wings 1/4 Red Eyes, Long Wings 1/4 Red Eyes, Long Wings

Explanation / Answer

--> DISCLAIMER :- There is a "mistake" in the question. In male offsprings, the last two lines are same/repeated. One of them should be "miniature wings" instead of long wings.

--> TERMS for ALLELES :-

--> To determine parents the genotypes of parents, we have to consider the inheritance of traits separately, as they are located on separate chromosomes; one on X-chromosome & the other on autosome.

a) X-linked allele : Wings length.

1)MALE OFFSPRINGS :- When you observe the phenotypes of male offsprings, there are both long wings and miniature wings. The fact is that male offsprings receive their only X-chromosome from their female parent. So, the female parent should have both alleles for wings length i.e., long as well as miniature wings, so that female parent can pass on them to her male offsprings.

=> Female parent genotype (up to now) is XL Xl.

2) FEMALE OFFSPRINGS :- When the female offsprings are observed for wings length, there are only long wings. The fact here is that the female offsprings receive one X-chromosome from each parent. Hence, the male parent should have allele for long wings on it's only X-chromosome.

Another explanation is that, the phenotype of male is long wings. The fact is that the male parent has only one X-chromosome which determines its phenotype. So, it has to be allele for long wings on male X-chromosome.

=> Male parent genotype (up to now) is XL Y.

b) Autosomal allele : Eyes colour.

1) FEMALE PARENT :- As the phenotype of female parent is sepia eyes (recessive) , the female parent genotype should be "ee".

2) MALE PARENT :- As there are both red eyes and sepia eyes in both male and female offsprings, the male parent should have autosomal alleles for both sepia and red eyes. Therefore, the male parent genotype should be "Ee".

FINAL ANSWER :

Female parent genotype = XL Xl e e.

Male parent genotype = XL Y E e.

==> My request : Please, mention feedback of my answer & doubts in my answer if any. Thank you :)

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