The inheritable characters that are determined by a gene located on the X-chromosome is

1. Analyze the question The question asks for the term used for inheritable characters whose genes are located on the X-chromosome (a sex chromosome).

2. Explain the concept Humans have 23 pairs of chromosomes. 22 pairs are autosomes, and 1 pair is the sex chromosomes (XX in females, XY in males). Genes carried on the sex chromosomes, especially the X-chromosome, control traits that are inherited along with sex. These traits are called sex-linked characters.

Examples:

• Colour blindness
• Haemophilia

These are usually recessive and appear more often in males. Males have only one X-chromosome, so a single recessive allele on it will show up. Females need two copies.

3. Work through the options

• A. Recessive: This describes how an allele behaves, not where it is located. Autosomal genes can also be recessive.
• B. Sex-linked: This describes traits whose genes are located on a sex chromosome (X). ✔
• C. Homozygous: This means having two identical alleles for a gene. It says nothing about location.
• D. Dominant: This describes allele expression, not chromosome location. Autosomal genes can be dominant too.

4. Answer The characters determined by genes on the X-chromosome are sex-linked, which is option B.

5. Exam tip Look at the clue words in the question. "Located on the X-chromosome" is about location, so the answer is sex-linked. Dominant, recessive and homozygous describe how alleles behave or pair up, not where the gene sits. Remember: X-linked = sex-linked = colour blindness and haemophilia.