Question

Balancers for chromosome 2 and 3 can be maintained together in the same stock, if the stock also carries dominant, visible alleles on the homologous non-balancer chromosomes. One such stock has a 2nd chromosome balancer (SM6, Cy) with the homolog carrying the dominant mutant allele of L (lobe eye), as well as a 3rd chromosome balancer (TM3, Sb) with a homolog carrying a dominant mutant allele of Ser (serrated wings)

(a) Using appropriate nomenclature, write out the genotype of BOTH a male and female from the double balancer stock.

(b) The male and female balancer stocks from (a) were crossed to generate an F1. Write out the genotype(s) and list the phenotype(s) of all viable F1 offspring.

Answer 1

Answer:

a. According to the scientific nomenclature standardized for Drosophila melanogaster, there are some rules which should be considered for naming the chromosomes and for writing the genotypes of drosophila. These rules are:

1. Firstly, to start writing a genotype, the initials of the balancer chromosome should be written. This should be followed by the number of chromosome representing the balancer chromosome.

2. For writing the multiple balancer chromosome in a row, the initials must be separated by a comma.

So, the genotypes of male and female genotype would be as follows:

b. The genotypes and the phenotypes of F1 generation are as follows: