While mitosis results in diploid daughter cells, meiosis results in haploid cells. Choose one of the following statements that best explains why meiosis results in haploid daughter cells rather than diploid daughter cells.
Group of answer choices
Nondisjunction during meiosis results in an abnormal number of chromosomes in the daughter cells.
Crossing over during meiosis results in the recombination of genetic material.
The parent cell in meiosis is haploid, whereas the parent cell in mitosis is diploid.
DNA replication does not occur prior to the second cell division during meiosis
The correct answer and explanation is :
The correct answer is:
DNA replication does not occur prior to the second cell division during meiosis.
Explanation:
Meiosis is a specialized form of cell division that reduces the chromosome number by half, resulting in four haploid daughter cells, each containing half the number of chromosomes as the parent cell. This reduction in chromosome number is essential for sexual reproduction, ensuring that when gametes (sperm or egg cells) fuse during fertilization, the resulting zygote has a diploid number of chromosomes.
The key factor that explains why meiosis results in haploid cells is the absence of DNA replication before the second division. Here’s a breakdown of the process:
- Meiosis consists of two divisions: Meiosis I and Meiosis II.
- In Meiosis I, homologous chromosomes (chromosomes from each parent) are separated into different cells. The chromosome number is reduced by half during this division, but each chromosome still consists of two sister chromatids.
- In Meiosis II, the sister chromatids of each chromosome are separated, similar to the process in mitosis, but there is no DNA replication between Meiosis I and Meiosis II.
- No DNA replication before Meiosis II: Unlike mitosis (where DNA replication occurs before both cell divisions), meiosis does not involve DNA replication before the second division (Meiosis II). This is critical because if DNA replication were to occur again, it would double the chromosome number, resulting in diploid daughter cells instead of haploid ones. By not replicating DNA between the two divisions, meiosis ensures that the chromosome number is halved, leading to haploid cells at the end of the process.
Thus, the lack of DNA replication before the second division is what ensures that meiosis results in haploid, not diploid, cells. This reduction is essential for maintaining the stability of the organism’s chromosome number across generations when fertilization occurs.