Question

Sex limited and sex-linked genes are located on.
A. Autosomes
B. X-chromosome
C. Y-chromosome
D. Both A and B

Answer 1

Hint: Sex-limited genes are expressed only one sex and it is turned off in other sex. Sex-linked genes are those traits which are influenced by genes on the sex chromosomes mainly X-chromosome.

Complete answer:
Sex-limited genes: These are those genes which are present in both the sexes but it is expressed only in one sex i.e., gene is present in one sex while it is present in another sex, for example, barred colouring in chickens which is only seen in roosters. These genes causes two sexes to show different phenotypes as it is expressed in only one sex. Also, sex-limited genes is restricted to autosomal traits.

Sex-linked genes: These genes are related to X-linked inheritance. Sex linked genes are located on sex chromosomes and it refers to traits which are influenced by genes on the X chromosomes. Sex-linked genes mostly affect males because they have a single copy of X chromosomes that carries the mutation while females with the second X gene counteract, for example, colour blindness and sickle cell anaemia.

If we look at options,
> Option A is Autosomes. Autosomes are non-sex chromosomes and sex limited genes are located on autosomes as these genes are restricted to autosomal traits. Thus, this option can be considered as it can be the right option but we need to look for sex-linked genes too and they are located on X-chromosomes.

> Option B is X-chromosomes. This option is also the correct one as sex-linked genes are located on sex chromosomes and mainly X-chromosome. Thus, we can consider this option too for sex-linked genes not for sex-limited genes.

> Option C is Y-chromosomes. Both sex-limited genes and sex-linked genes are not located on Y-chromosomes and hence this option is incorrect.

> Option D is Both A and B. This is the correct option since sex-limited genes are located on autosomes and sex-linked genes are located on X-chromosomes which makes this option the correct one.

Hence, the correct answer is option (D).

Note: Sex-limited genes are restricted to autosomes and sex-linked are located on sex chromosomes i.e., mainly on X chromosomes and due to which D option is correct and both of these are not located on X-chromosomes. Sex-linked genes mostly affect males due to the presence of one X-chromosome.