CH 17: Cell Cycle, Control System and Meiosis

Flashcards on Cell Cycle and Meiosis

Mitotic Index

A ratio used to estimate the proportion of cells in a population undergoing mitosis. It serves as an indicator of cell proliferation.

Flow Cytometry

A laboratory technique employed to measure the characteristics of cells in a liquid stream as they pass through a beam of light. It's used to quantify DNA content and identify cells in different phases of the cell cycle.

S Phase

The period within the cell cycle where the replication of DNA occurs, resulting in two identical copies (sister chromatids) of each chromosome.

M Phase

The stage of the cell cycle encompassing mitosis and cytokinesis, during which the nucleus divides and chromosomes are segregated, ultimately leading to cell division.

G1 and G2 Phases

Intervals within the cell cycle positioned between S phase and M phase. These phases provide time for cell growth and monitoring of both intracellular and extracellular conditions to ensure the cell is ready to proceed to the next phase.

Cyclin-Dependent Kinases (Cdks)

A family of protein kinases that regulate the cell cycle. Their activity is dependent on the binding of cyclin subunits; these complexes phosphorylate target proteins that drive cell cycle progression.

S-Cdk

A specific cyclin-Cdk complex that promotes the initiation of DNA replication during the S phase of the cell cycle.

M-Cdk

A cyclin-Cdk complex that triggers entry into mitosis by phosphorylating proteins involved in chromosome condensation, nuclear envelope breakdown, and spindle formation.

Cdk Inhibitor Proteins (CKIs)

A class of proteins that can bind to cyclin-Cdk complexes, inhibiting their kinase activity. This provides a mechanism for controlling progression through the cell cycle in response to internal and external signals.

APC/C

An enzyme, specifically a ubiquitin ligase, that mediates the ubiquitylation and subsequent degradation of cell-cycle regulators, including securin and mitotic cyclins, ensuring proper progression through the cell cycle.

Cohesin

A multi-subunit protein complex that mediates sister chromatid cohesion from S phase through metaphase, ensuring proper chromosome segregation during cell division.

Topoisomerase II

An enzyme that resolves DNA tangles that arise during replication by cutting and resealing DNA strands, preventing DNA damage and ensuring proper chromosome segregation.

Mitosis

A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

Cytokinesis

The process of cell division that follows mitosis, where the cytoplasm of a single cell is divided into two separate daughter cells.

Contractile Ring

A dynamic structure, composed mainly of actin and myosin filaments, that forms during cytokinesis to constrict the middle of the cell, eventually pinching it into two daughter cells.

Meiosis

A special type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell. This process is essential for sexual reproduction.

Nondisjunction

The event where chromosomes fail to separate correctly during cell division, resulting in daughter cells with an abnormal number of chromosomes.