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: -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-4: -Meiosis II begins with the 2 haploid cells where each chromosome is made up of two connected sister chromatids. DNA replication does NOT occur at the beginning of meiosis II. The sister chromatids are separated, producing 4 genetically different haploid cells.

Detailed explanation-5: -DNA replication takes place in S-phase of the Interphase before Meiosis I begins.