Chapter 13, Problem 17P

Summary Introduction

To analyze:

a) Considering random segregation of the chromosome, determine the genotype and proportion of the sperm produced by the trisomic male fruit fly with genotype $\text{++ey}$.

b) Determine the expected ratio of the eyeless to normal eyed flies produced by the union of the sperm with the egg having genotype eyey producing an eyeless phenotype.

Introduction:

The segregation of the chromosome during cell division is an important phenomenon. If the chromosome fails to segregate properly, it is called non-disjunction, and it could have resulted in the daughter cell with one extra chromosome ($\text{n+1}$) and the other with a missing chromosome ($\text{n-1}$) condition.

The cell with improper distribution of the chromosomes may reduce their survival rate as compared to the normal cell. In the germ cells, non-disjunction results in the formation of gametes with extra or missing chromosomes which leads to the production of aneuploidy gametes. Germ cells, egg or sperms, are haploid cells, containing a single pair of chromosome. The condition of the presence of extra chromosome ($\text{2n+1}$) in the zygote due to the union of aneuploid gamete with a normal haploid gamete is known as trisomy.