Question

In the fruit fly Drosophila, the gene 'T' for tan body color is dominant to its allele 't' for ebony body color. At another gene locus on the same chromosome the gene 'B' for normal bristles is dominant to its allele 'b' for short bristles. Two flies are crossed that both have the same genotype: the alleles 'T' and 'B' are on one chromosome and the alleles 't' and 'b' are on the homologous chromosome. If we assume that no crossing over occurs between these two gene loci, what proportion of the offspring are expected to have normal bristles and tan body color?

Answer 1

When two fruit flies with the genotype Tb/tb are crossed and no crossing over occurs, all offspring will exhibit the dominant phenotypes of tan body color (T) and normal bristles (B), as alleles on the same chromosome are inherited together.

Step-by-step explanation:

In Drosophila, a fruit fly, the gene 'T' for tan body color is dominant over its allele 't' for ebony body color. Similarly, the gene 'B' for normal bristles is dominant over its allele 'b' for short bristles.

When two fruit flies with the same genotype (Tb and tb on a pair of homologous chromosomes) are crossed, and assuming no crossing over occurs between these two gene loci, all of the offspring will have normal bristles and tan body color.

This is because the alleles are linked on the same chromosome and will be inherited together, as described in Figure 13.3, demonstrating inheritance patterns of linked genes.