Question

Traits controlled by genes present on the X-chromosome are called.
a. Sex limited
b. Sex influenced
c. Autosomal
d. Sex-linked

Answer 1

Hint: Chromosomes are the structures that are found in the nucleus of the cells, they are nothing but genes, whereas trait is a genetically determined characteristic that is controlled by one or more genes.

Complete answer:
- Chromosomes in humans are classified as autosomes and sex chromosomes,
- The number of autosomes in each cell is 44, whereas two sex chromosomes are present.
- If the cell consists of the XX chromosome, the person is male, and if it consists of XY chromosomes, the person is female.
- So these sex chromosomes, have gene traits that tell about the gender.
- Along with this sex chromosomes also carry so many genetic traits. If anyone these genetic traits are carried by the sex chromosomes is called sex-linked.
- Man consists of one X chromosome, so if any trait of X linked chromosome is shown in the Phenotype by man, as they do not have another gene to mask this trait, even if the trait is dominant or recessive, they can be expressed in X-linked.
- If any trait on the X chromosome on females is mostly not expressed, as females consist of XX so the expression is masked, so for most of the X-linked traits females are carriers.
- As Y chromosomes are present in males only, those linked traits are expressed by only males.
- Sex limited traits are those, in which genes are present on both sexes, but their expression is limited to only one sex. Example milk in cattle. So it is the wrong answer.
- Sex influenced traits in which autosomes plays role in expressing the gene, and in one sex a single recessive gene can also express the trait, and it other sex if requires two genes of the same traits to carry the expression, for example, is bald in males.
- Autosomes are chromosomes that are not linked to the sex of an individual.
So from all the above explanations, Sex-linked is the correct answer.

Hence, the correct answer is option (D).

Note: A gene present on the sex chromosome is called a sex-linked trait because the expression of these gene traits depends on the sex of an individual. And there so many X linked and Y linked traits, wherein most of X linked traits females are carriers.