Unit 5 Overview: DNA and Cell Cycle

This set of flashcards covers key vocabulary and concepts related to DNA and the cell cycle, essential for understanding unit 5 in biology.

Cell Cycle

The ordered sequence of events, including Interphase (G1, S, G2 phases) and the M phase (mitosis and cytokinesis), through which a cell replicates its DNA and divides into two daughter cells.

Interphase

The longest phase of the cell cycle, during which the cell grows, copies its DNA, and prepares for cell division. It is divided into G1, S, and G2 phases.

G1 Phase

The 'first gap' or 'growth' phase of Interphase, where the cell grows, synthesizes proteins, and carries out its normal metabolic functions.

S Phase

The 'synthesis' phase of Interphase, where the cell replicates its entire DNA content in preparation for cell division, following the principle of semi-conservative replication.

G2 Phase

The 'second gap' or 'growth' phase of Interphase, where the cell continues to grow, synthesizes proteins and organelles, and prepares all necessary components for mitosis.

G0 Phase

A quiescent phase where cells exit the cell cycle and cease dividing. Cells in this phase can remain dormant or re-enter the G1 phase under specific conditions.

Mitosis

The process of nuclear division within the M phase of the cell cycle, resulting in two genetically identical nuclei. It consists of Prophase, Metaphase, Anaphase, and Telophase (PMAT).

Prophase

The first and longest phase of mitosis, where chromosomes condense and become visible, the nuclear envelope breaks down, and the spindle fibers begin to form.

Metaphase

The second phase of mitosis, characterized by the alignment of condensed chromosomes along the metaphase plate (equatorial plane) of the cell.

Anaphase

The third phase of mitosis, during which sister chromatids separate and are pulled apart towards opposite poles of the cell by the shortening spindle fibers.

Telophase

The final phase of mitosis, where the chromosomes arrive at the poles and begin to decondense, the nuclear envelope reforms around each set of chromosomes, and the spindle fibers disappear.

Cytokinesis

The final stage of the cell cycle, which usually overlaps with telophase, involving the division of the cytoplasm to form two separate daughter cells.

DNA

An organic molecule containing the genetic instructions that are replicated during the S phase of the cell cycle and passed on to daughter cells.

Semi-Conservative Replication

The mechanism by which DNA is duplicated during the S phase, resulting in two new DNA molecules, each containing one original (parental) strand and one newly synthesized (daughter) strand.

Sister Chromatids

Two identical copies of a chromosome joined together by a centromere, formed during the S phase and separated during anaphase of mitosis.

Spindle Fibers

Microtubule structures that form the mitotic spindle, responsible for separating sister chromatids during anaphase and moving them to opposite poles of the cell.

Regulatory Proteins

Proteins that function as internal and external checkpoints to ensure the correct progression of the cell cycle, preventing errors like uncontrolled cell division.

Cell Cycle Checkpoints

Specific points in the cell cycle (e.g., G1, G2, M) where regulatory proteins assess internal and external conditions to decide whether the cell should proceed to the next phase or pause/exit the cycle.

Cancer

A disease caused by uncontrolled cell division and an unregulated cell cycle, leading to the formation of malignant tumors.