Which chromosome pair determines the sex of a child?

• A. X and Y chromosomes
• B. Chromosome pair 21
• C. Chromosome pair 18
• D. Chromosome pair 13

Answer: (A)

Verified step by step guidance

1. Understand that humans have 23 pairs of chromosomes, with each pair consisting of one chromosome from each parent.
2. Recognize that the 23rd pair of chromosomes is known as the sex chromosomes, which determine the biological sex of an individual.
3. Identify that the sex chromosomes are labeled as X and Y. Typically, females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
4. Note that the other chromosome pairs, such as pair 21, pair 18, and pair 13, are autosomes and do not determine sex.
5. Conclude that the X and Y chromosomes are responsible for determining the sex of a child, with the presence of a Y chromosome typically resulting in a male child.