Question

A recessive mutant allele, black, causes a very dark body in Drosophila when homozygous. The normal wild-type color is gray. A black female is crossed to a heterozygous gray male. What are the parental genotypes? What F1 phenotypic and genotypic ratios are produced from this cross?
really want to understand this and I am just so lost. lecture is not helping

Answer 1

You arbitrarily assign symbols to the alleles:
B= dominant allele
b= recessive allele

So we have:
BB= dominant phenotype, grey
Bb=dominant phenotype, grey
bb=recessive phenotype, black

Now we have a heterozygous male (Bb) mated with a recessive female (bb),

Bb x bb, we set up a punnett square:



do you know how to fill them in?

Answer 2

Bb-Bb
bb-bb