Final answer:
The S phase of the cell cycle is critical for DNA replication, producing sister chromatids that later separate during mitosis, ensuring each daughter cell has a complete set of chromosomes. The G2 phase prepares the cell for mitosis, while cohesin proteins maintain the integrity of the chromatids until separation.
Step-by-step explanation:
Phases of the Cell Cycle and Chromosome Duplication
During the cell cycle, interphase precedes mitosis and consists of the G1, S, and G2 phases. The S phase (synthesis phase) is crucial for DNA replication, where each chromosome duplicates to form two sister chromatids attached at a central point called the centromere. The resulting chromatids then make up a duplicated chromosome. The G2 phase follows DNA replication, in which cells prepare for mitosis. This phase is shorter and involves synthesizing proteins needed for chromosome condensation and mitotic spindle formation.
The structure of chromosomes changes during the cell cycle; prior to DNA replication, each chromosome has one chromatid. Post replication, each consists of two sister chromatids. The human cell, with 46 chromosomes, will have 92 chromatids, as DNA content doubles. Cohesin proteins are vital as they hold the chromatids together at the centromere until they are ready to separate during mitosis, ensuring each daughter cell receives one copy of each chromosome.
In mitosis, which includes the phases of prophase, metaphase, anaphase, and telophase, the sister chromatids are pulled apart into individual chromosomes and evenly distributed to the resulting daughter cells. This process is essential for cell proliferation and tissue growth. Meiosis, on the other hand, involves a similar but more complex process tailored to producing genetically varied germ cells essential for sexual reproduction.