Recording-2025-03-09T07_34_55.645Z

Overview of the Cell Cycle

• The mitotic cell cycle is essential for cell growth, repair, and maintenance in eukaryotic organisms.

• Regulated to prevent uncontrolled cell division and DNA replication errors, which can lead to diseases such as cancer.

Phases of the Cell Cycle

• Divided into four main phases: G1, S, G2, and M.

  • Interphase: G1, S, and G2 phases where the cell prepares for division.

  • Mitotic Phase: Represents the division process (M phase).

Synchronous vs. Asynchronous Cell Populations

• Synchronous Population: All cells in the same phase of the cell cycle.

• Asynchronous Population: Cells are at various stages of the cell cycle.

Quiescent Phase (G0)

• Cells may enter a non-dividing stage known as G0, performing their normal functions without growing or dividing.

G1 Phase (Gap 1)

• Involves cell growth and preparation for DNA replication.

• Checks for DNA damage, nutrient availability, and cell size.

• Proteins prepare origins of replication and load helicases.

  • Cells have 46 homologous chromosomes (2n) and 2c DNA content

S Phase (Synthesis)

• DNA replication occurs.

• DNA helicases separate double-stranded DNA, allowing replication to occur.

• Each chromosome is duplicated, leading to 46 pairs of sister chromatids.

  • Chromosome Count: 46 (2n) with 4c DNA content post-replication.

G2 Phase (Gap 2)

• Prepares the cell for mitosis (M phase).

• Ensures S phase was completed correctly with no DNA damage.

  • Chromosome Count: 46 unique homologous chromosomes (2n), still in sister chromatid form.

M Phase (Mitosis)

• Metaphase: Sister chromatids align at the cell's equator; mitotic spindle ensures equal chromosome segregation.

• Telophase: Nuclear envelope reforms around segregated chromosomes, chromosomes condense.

• Cytokinesis: Division of cytoplasm creating two daughter cells, each with 46 unique homologous chromosomes (2n) and 2c DNA content.

Regulation of the Cell Cycle

• Involves cyclins and cyclin-dependent kinases (CDKs) that dictate cell cycle phases.

• Checkpoints ensure one phase is completed before the next begins, preventing issues such as incomplete DNA replication from proceeding.

Importance of the Cell Cycle

• Vital for growth, repair, and overall health.

• Understanding the phases and regulation of the cell cycle is crucial in preventing diseases like cancer.