Answer :
To explain how the total number of chromosomes changes during meiosis and how it compares in the zygote, gametes, and original parent cell, we need to understand the process of meiosis.
1. Meiosis is a type of cell division that produces gametes (sperm and egg cells) in sexually reproducing organisms.
2. In meiosis, a parent cell with a diploid number of chromosomes (2n) undergoes two rounds of division, resulting in four daughter cells, each with half the number of chromosomes as the parent cell (n).
3. During meiosis I, homologous chromosomes pair up and exchange genetic material in a process called crossing over. This leads to genetic variation.
4. In meiosis II, the sister chromatids of each chromosome are separated, resulting in four haploid daughter cells, each with a unique combination of chromosomes.
Now, let's compare the total number of chromosomes in different stages:
- Original parent cell: It has a diploid number of chromosomes (2n). For example, in humans, a diploid cell has 46 chromosomes.
- Gametes: After meiosis, gametes have a haploid number of chromosomes (n). In humans, sperm and egg cells have 23 chromosomes each.
- Zygote: When a sperm fertilizes an egg during sexual reproduction, the zygote formed has a diploid number of chromosomes (2n). So, in humans, the zygote will have 46 chromosomes, the same as the original parent cell.
In summary, during meiosis, the total number of chromosomes is reduced by half, leading to the formation of haploid gametes. When fertilization occurs, the zygote is formed with a diploid number of chromosomes, the same as the original parent cell.
