Which of the following holds true about meiosis? I. It...

Which of the following holds true about meiosis? I. It ensures the production of haploid phase in the life cycle of sexually reproducing organism where fertilization restores the diploid phase. II. It involves the two sequential cycle of nuclear and cell division called meiosis I and II but only a single cycle of DNA replication. III. It involves the pairing of homologous chromosomes and recombination between them. IV. Four haploid cells are formed at the end of meiosis. (a) I, II, IV only (b) IV only (c) I and III only (d) All of these

Which of the following holds true about meiosis?
I. It ensures the production of haploid phase in the life cycle of sexually reproducing organism where fertilization restores the diploid phase.
II. It involves the two sequential cycle of nuclear and cell division called meiosis I and II but only a single cycle of DNA replication.
III. It involves the pairing of homologous chromosomes and recombination between them.
IV. Four haploid cells are formed at the end of meiosis.
(a) I, II, IV only
(b) IV only
(c) I and III only
(d) All of these

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Key Concepts

Meiosis

Meiosis is a specialized form of cell division that reduces the chromosome number by half, leading to the formation of haploid cells. This process is fundamental to sexual reproduction, ensuring genetic diversity and the correct restoration of diploid numbers when gametes fuse during fertilization.

Haploid and Diploid Stages

In the life cycle of sexually reproducing organisms, cells alternate between haploid and diploid phases. Meiosis produces haploid cells (gametes) from diploid precursor cells, while fertilization restores the diploid state, maintaining a consistent number of chromosomes across generations.

DNA Replication and Division Cycles in Meiosis

A key feature of meiosis is that DNA replication occurs only once, followed by two successive rounds of cell division. The first division (meiosis I) separates homologous chromosomes, while the second division (meiosis II) separates sister chromatids, resulting in four haploid cells.

Homologous Chromosome Pairing and Recombination

During prophase of meiosis I, homologous chromosomes pair up and undergo genetic recombination through crossing over. This interaction not only allows for the exchange of genetic material between chromosomes but also contributes significantly to genetic variation in the resulting gametes.

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