PROBLEM 3 4. Show the Punnett square for the cross of a homozygous red eyed female and a white eyed male. Eye color in flies is sex linked

Drosophila flies exhibit the XX and XY type of sex-determination. 

In this type of sex determination, the females have two X chromsomes and males have one X and one Y chromsomes in their genotype. 

As the males have only one X chromosome (as the males do not have another homologous X chromosome), whatever the allele on X chromosome, irrespective of its condition (it may be either dominant or recessive), it can be expressed. 

In the case of females, the expression is depends. The presence of at least one dominant allele at the locus gives the dominant phenotype. The recessive phenotype will be expressed if both X chromosomes have recessive alleles at the same locus.