The Genes for Light Eyes (Lt; Light)and Straw Bristles (Stw;

Essay

The genes for light eyes (lt; light)and straw bristles (stw; straw)are tightly linked on chromosome 2 in Drosophila melanogaster.The Malpighian tubes of lt larvae and adults are maternally affected in that Malpighian tubes of lt/lt organisms,whose mothers were lt⁺/ˡᵗ and have more yellow pigment than those from lt/lt mothers.There is no maternal effect associated with the straw locus.Give the phenotypes of the offspring from the following crosses.
$\begin{array}{lll}& \underline{\text { Female }} & \underline{\text { Male }} \\\text { Cross \#1: } & l t \text { stw/lt stw } & l t^{+} \text {stw } w^{+} / l t \text { stw } \\\text { Cross \#2: } & l t^{+} s t w / l t \text { stw } & l t \text { stw } w^{+} / l t s t w \\\text { Cross \#3: } &l t^{+} s t w w^{+} / l t \text { stw } & \text { lt stw/lt stw }\end{array}$