Bio U2: Eukaryotic Cell Cycle

Cell Cycle: Interphase (G1, S, G2) Mitotic phase (P, M, A, T, C)

Interphase

During interphase, the cell prepares itself for division by growing, replicating its DNA, and synthesizing necessary proteins. It is further divided into: G1, S, G2

Ip: G1 (gap 1)

This phase follows cell division and represents the period of growth and preparation for DNA replication. During G1, the cell synthesizes proteins, RNA, and other molecules necessary for cell growth and function. The duration of G1 can vary greatly among different cell types and environmental conditions.

Ip: S (synthesis)

The S phase is characterized by DNA synthesis, where the cell's genetic material is replicated. Each chromosome is duplicated, resulting in the formation of sister chromatids, which are held together at the centromere. Replication occurs in a semi-conservative manner, ensuring that each daughter cell receives an identical copy of the genetic material.

Ip: G2 (gap 2)

Following DNA replication, cells enter the G2 phase, which is marked by further growth and preparation for cell division. The cell continues to synthesize proteins, RNA, and organelles to support the upcoming division.

Mitotic phase

The M phase is the last phase of the cell cycle and consists of two main processes: mitosis and cytokinesis. Mitosis is divided into several sub-phases: prophase, metaphase, anaphase, telophase, and cytokinesis (physical division of the cytoplasm)

Mp: Prophase

Chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and spindle fibers begin to form.

Mp: Metaphase

Chromosomes align along the metaphase plate at the center of the cell.

Mp: Anaphase

Sister chromatids separate and move towards opposite poles of the cell, pulled by the spindle fibers.

Mp: telophase

Chromosomes decondense, nuclear envelopes reassemble around each set of chromosomes, and the mitotic spindle breaks down.

Cytokinesis

follows mitosis and involves the physical division of the cytoplasm to produce two daughter cells. In animal cells, cytokinesis involves the formation of a cleavage furrow. In plant cells, a cell plate forms to divide the cytoplasm.

cell cycle diagram

what is the purpose of the cell cycle?

Replaces damaged, worn-out, or dead cells in tissues like skin, blood, and the intestinal lining.

Serves as the primary method of reproduction for single-celled organisms.

Ensures that each new daughter cell receives an exact, undamaged copy of the organism's DNA.

mitosis vs. meiosis

mitosis:

occurs in all organisms (except viruses), makes all bodily (somatic) cells, 1 cell division, makes 2 diploid daughter cells that are genetically identical to each other/parent, creates human cell with 46 chromosomes

meiosis:

occurs in plants/animals/fungi, creates sex cells (gametes), 2 sequential cell divisions, makes 4 haploid daughter cells that are genetically different, creates human cells with 23 chromosomes

both:

occurs in plant/animal cells, starts with diploid parent cell, produces new cells, cells undergo dna replication, same basic steps

haploid vs. diploid

haploid: cell that contains a single set of unpaired chromosomes (n). gametes.

diploid: cell that contains two complete sets of chromosomes (2n). somatic cells.