AP BIOLOGY

Detailed explanation-1: -Before meiosis begins, during S phase of the cell cycle, the DNA of each chromosome is replicated so that it consists of two identical sister chromatids, which remain held together through sister chromatid cohesion. This S-phase can be referred to as “premeiotic S-phase” or “meiotic S-phase".

Detailed explanation-2: -Before meiosis begins, the DNA in each chromosome is replicated. The two identical copies that result from this DNA replication are referred to as ‘sister chromatids’, and are joined to each other by a region of the chromosome called the centromere (as shown in figure 1).

Detailed explanation-3: -DNA replication occurs in both mitosis and meiosis. In meiosis, the cell undergoes two divisions, i.e. meiosis I and II. Meiosis I is reduction division and meiosis II is similar to mitosis but DNA replicates only once during meiosis, i.e. before meiosis I in S phase.

Detailed explanation-4: -Before entering meiosis I, a cell must first go through interphase. This is the same interphase that occurs before mitosis. The cell grows, copies its chromosomes and prepares for division during the G 1start subscript, 1, end subscript phase, S phase, and G 2start subscript, 2, end subscript phase of interphase.

Detailed explanation-5: -Meiosis, divided into meiosis I and meiosis II, is a process in which a diploid cell divides itself into four haploid cells. Note that meiosis II immediately follows meiosis I; DNA replication does not occur after meiosis I.