Cell Cycle Quiz - Interphase Overview

Interphase

• Interphase is the longest phase of the cell cycle, encompassing the period between cell divisions.
• It's not a period of inactivity but rather a time of intense cellular activity where the cell prepares for cell division.
• Divided into three subphases: G1, S, and G2.

G1 Phase (Gap 1)

• Characterized by significant cellular growth.
• The cell synthesizes proteins and organelles.
• The cell increases in size and mass.
• Critical checkpoint for determining whether or not the cell will proceed to DNA replication (S phase).
• Cell checks if the environment is favorable and if the necessary resources are present for DNA replication.
• Unsuitable conditions or damaged DNA can cause the cell to enter a resting phase (G0).

S Phase (Synthesis)

• DNA replication occurs in the nucleus during this phase.
• Each chromosome duplicates, forming two identical sister chromatids.
• The resulting chromosomes are genetically identical to each other.
• Histones and other proteins necessary for DNA structure are simultaneously synthesized.

G2 Phase (Gap 2)

• The cell continues to grow and synthesize proteins.
• Important for duplicating organelles and finalizing preparation for mitosis.
• The cell checks for DNA replication errors and repairs any that are found.
• Cell also checks if the DNA replication has occurred entirely and accurately.
• The cell ensures all the necessary structures (ex. centrosomes) are duplicated for division.

Mitosis

• Mitosis is the process of nuclear division where two genetically identical daughter nuclei are created from a single parent nucleus.
• Four distinct phases: prophase, metaphase, anaphase, and telophase.

Prophase

• Chromosomes condense and become visible under a microscope.
• The nuclear envelope begins to break down.
• Spindle fibers start to form outside the nucleus.
• Duplicated centrosomes move to opposite poles of the cell and assemble spindle fibers.

Metaphase

• Chromosomes align at the metaphase plate in the center of the cell.
• Spindle fibers attach to the centromeres (the region that joins sister chromatids).

Anaphase

• Sister chromatids separate and are pulled to opposite poles of the cell by the shortening spindle fibers.
• The cell begins to elongate.

Telophase

• Chromosomes decondense and become less visible.
• New nuclear envelopes begin to form around each set of separated chromosomes.
• Spindle fibers disappear.
• Cytokinesis can occur during telophase or immediately after.

Cytokinesis

• Cytokinesis is the division of the cytoplasm that follows upon mitosis.
• Formation of the cleavage furrow in animal cells, and a cell plate in plant cells.
• Two genetically identical daughter cells are formed from the single parent cell.