What are allosomes?

In Barr body (sex-chromatin) of a normal female:

Distinguish between: Sex determination in humans and Sex determination in Drosophila.

$A$ fruit fly is heterozygous for a sex-linked gene. It is crossed with a normal female fruit fly. The specific chromosome for the male enters the egg in the ratio of ............. (in $: 1$)

Organism with male heterogamety $- P$
Organism with female heterogamety $- Q$
$I -$ Human,$II -$ Bird,$III -$ Drosophila,$IV -$ Grasshopper
Select the correct option for $P$ and $Q$.
$\quad P \quad\quad Q$

$A$ recessive gene present on the non-homologous part of only one $X$ chromosome of humans will . . . . . . .