Why is DNA replication necessary before meiosis begins?

Sourav PanNovember 8, 2024

Answered

DNA replication is a critical process that occurs before meiosis begins, primarily for the following reasons:

Purpose of DNA Replication in Meiosis

1. Preparation for Chromosome Segregation: Before meiosis can occur, a diploid cell must replicate its DNA to ensure that each chromosome consists of two identical sister chromatids. This replication occurs during the S phase of the cell cycle, resulting in chromosomes that are ready for the complex process of segregation during meiosis I. Each homologous chromosome pairs with its duplicate, forming structures known as bivalents, which are essential for proper segregation and genetic recombination.
2. Facilitating Genetic Recombination: The replicated chromosomes undergo homologous recombination during prophase I of meiosis. This process involves the exchange of genetic material between homologous chromosomes, increasing genetic diversity in the resulting gametes. Without prior DNA replication, there would be insufficient genetic material for this crucial exchange to occur.
3. Ensuring Correct Chromosome Number: Meiosis reduces the chromosome number by half to produce haploid gametes (sperm and eggs). The initial replication ensures that when the chromosomes are segregated during meiosis I and II, each gamete receives one complete set of chromosomes. If DNA replication did not occur beforehand, gametes could end up with an incomplete set of genetic information, leading to aneuploidy (abnormal chromosome numbers) which can cause miscarriages and developmental disorders.

Summary of Meiosis Process

• Meiosis I: Involves pairing of homologous chromosomes and their subsequent segregation into two daughter cells.
• Meiosis II: Follows without any further DNA replication and involves the separation of sister chromatids into four haploid cells.