Practicing Success
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CUET Preparation Today
At what stage, does the number of chromosomes become half? |
Diplotene Telophase I Prophase I Anaphase I |
Anaphase I |
The correct answer is Option (4) -Anaphase I The production of offspring by sexual reproduction includes the fusion of two gametes, each with a complete haploid set of chromosomes. Gametes are formed from specialised diploid cells. This specialised kind of cell division that reduces the chromosome number by half results in the production of haploid daughter cells. This kind of division is called meiosis. Meiosis ensures the production of haploid phase in the life cycle of sexually reproducing organisms whereas fertilisation restores the diploid phase. We come across meiosis during gametogenesis in plants and animals. The number of chromosomes becomes half during the first meiotic division, also known as meiosis I. Specifically, it occurs during a stage called "anaphase I." During anaphase I, the homologous pairs of chromosomes, which each consist of two sister chromatids, are separated and pulled to opposite poles of the cell by spindle fibers. This results in each daughter cell receiving one set of chromosomes, which is half the number of chromosomes present in the parent cell. After meiosis I, there is a brief interphase known as interkinesis, which is similar to the G1 phase of the cell cycle. The chromosomes do not replicate during interkinesis, so the number of chromosomes remains the same. The second meiotic division, or meiosis II, then separates the sister chromatids, resulting in the formation of four haploid daughter cells, each with a single set of chromosomes.
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