4. In Drosophila, the gene spineless maps to the third
chromosome, while brown and purple are both on the second
chromosome 6cM apart. Consider the alleles ss, b and p with
recessive phenotypes –spineless bristles (ss), brown body (b) and
purple eyes (p). What frequencies would you expect for the various
phenotypes amongst the offspring of the testcross (note that comma
separates alleles on the same chromosome, semicolon separates
different chromosomes): +, + / b, p ; +/ss x b, p / b, p ; ss/ss
(testcross)