Task

In Drosophila, grey body (B) is dominant over black (b) and normal wings (V) over vestigial (v); both genes are on one autosome. A grey normal-winged female heterozygous for both genes (dominant alleles from her father, recessive from her mother) was crossed with a black vestigial male. The offspring were 415 grey normal, 405 black vestigial, 92 grey vestigial and 88 black normal flies. 1) State Morgan’s law of linked inheritance and the concept of linkage groups. 2) Explain crossing over, its place in meiosis and its relation to the distance between genes. 3) Write the cross (in chromosome form), show crossover and non-crossover gametes and describe how the distance is determined. 4) Calculate the number and share (%) of recombinant offspring. 5) Determine the distance between the genes (in map units, morganids). 6) Calculate the female’s gamete types and their percentages. 7) If the same female is crossed with a grey normal-winged male of genotype BV/bv, what share (%) of the offspring will be black vestigial (male Drosophila have no crossing over)? For each part, write out the law or method used (cross scheme, formulas, reasoning) and all calculations step by step.