In which of the following organisms is male heterogamety absent?

On which of the following can a single recessive trait express its effect?

Given below are two statements.
Statement $I$ - $X$ Chromosome has a large amount of euchromatin and a small amount of heterochromatin.
Statement $II$ - The homologous region of the $X$ Chromosome contains a smaller number of genes than the $Y$ Chromosome.
In the light of the above statements,select the correct option given below:

Assertion : In humans,the gamete contributed by the male determines whether the child produced will be male or female.
Reason : Sex in humans is a polygenic trait depending upon a cumulative effect of some genes on $X-$ chromosome and some on $Y-$ chromosome.

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

The character of organisms is said to be sex-linked when its gene is carried on: