A true breeding vestigial-winged female was crossed with a true breeding...

A true breeding vestigial-winged female (vg vg, ri+ri+) was crossed with a true breeding male fly with incomplete wing veination (vg+vg+,ri ri). All the F1 progeny were wild type. The F1 flies were allowed to interbreed and the table overleaf shows the phenotypes of the F2 generation

Phenotype Number
Wild type
552
Vestigial wing
284
Incomplete wing vein
173

Explain why there are only three visible phenotypes rather than four. What is this phenomenon called?

Cross 7

Starting from the parental cross shown below, write out the genotypes, phenotypes and sex of the F1 progeny and fill in the Punnett square to show the genotypes, phenotypes and sex of the F2 progeny. Note that X = the X chromosome and Y = the Y chromosome.

Parental        vg vg, Xw+Xw+                         x            vg+vg+, XwY
                      Vestigial-winged female                         White eyed male

F1 Genotypes =
F1 Phenotypes =
F1 Sex =

F2 Genotypes, phenotypes and sexes displayed in a Punnett square






 

What is unusual about the phenotypic ratios shown in this F2 and what is the cause of this effect? Do the alleles of the white gene segregate independently of the vestigial gene?