Question

which of the following statements about humans is true?
human life cycles alternate between fertilization and meiosis, with meiosis producing haploid zygotes.
at sexual maturity, ovaries and testes produce diploid gametes by meiosis.
the 23rd pair, the sex chromosomes, determines whether the person is female (xx) or male (xy).
an ovum and sperm unite during fertilization, forming a haploid (n), single - celled zygote.

Explanation:

• For the first option: Meiosis produces haploid gametes (sperm and egg), not zygotes. Zygotes are formed by fertilization (diploid).
• For the second option: Gametes (sperm and egg) produced by ovaries and testes are haploid, not diploid. Meiosis reduces chromosome number by half.
• For the third option: The 23rd pair of chromosomes (sex chromosomes) - XX in females and XY in males - determines biological sex.
• For the fourth option: Fertilization of an ovum (n) and sperm (n) forms a diploid (2n) zygote.

Answer:

The 23rd pair, the sex chromosomes, determines whether the person is female (XX) or male (XY).