9. In the human life cycle, only sperm and eggs have which number of chromosomes?
Answer: D
Sperm and eggs have haploid chromosomes.
In the human life cycle, sperm and eggs contain haploid chromosomes, which means they have one set of chromosomes (23 in humans), half the number found in diploid cells.
A) Diploid
Diploid cells contain two sets of chromosomes, one from each parent, totaling 46 chromosomes in humans. This option is incorrect because sperm and eggs do not have diploid numbers; they are formed through meiosis, which reduces the chromosome number to haploid.
B) Polyploid
Polyploid cells have more than two sets of chromosomes. This option is not applicable to human sperm and eggs, as they do not possess multiple sets of chromosomes but rather a single set, making this choice incorrect.
C) Monoploid
Monoploid refers to cells with only one complete set of chromosomes, which is similar in definition to haploid. However, the term is less commonly used in the context of human gametes. While it could be argued that monoploid is technically correct, haploid is the more accurate and widely accepted term for describing the chromosome number in sperm and eggs.
D) Haploid
Haploid is the correct term for sperm and eggs, which contain a single set of chromosomes (23 chromosomes in humans). This is essential for sexual reproduction, as it allows for the restoration of the diploid number when sperm and egg fuse during fertilization.
Conclusion
The correct answer is haploid, as it accurately describes the chromosome composition of human sperm and eggs. All other options fail to correctly represent the number of chromosomes present in these gametes, which are crucial for maintaining genetic diversity and stability in the human life cycle.