Chapter 11 – Cell Cycle, Mitosis & Meiosis

Replication

The process of copying DNA before a cell divides.

Segregation

The separation of DNA copies into two new cells.

Cytokinesis

The division of the cytoplasm into two daughter cells after nuclear division.

Binary fission

A form of asexual reproduction in prokaryotes where the cell divides into two identical cells.

DNA

Deoxyribonucleic acid, the molecule that stores genetic information.

Chromosomes

Structures made of DNA and proteins that contain genetic information.

Sister chromatids

Identical copies of a chromosome connected by a centromere.

Mitosis

A type of nuclear division that results in two genetically identical daughter cells.

Meiosis

A type of nuclear division that results in four non-identical gametes.

Cell cycle

The ordered sequence of events in the life of a cell, including growth and division.

G1

First gap phase; cell grows and prepares for DNA replication.

S

Synthesis phase; DNA is replicated.

G2

Second gap phase; cell prepares for mitosis.

Interphase

Portion of the cell cycle that includes G1, S, and G2 phases.

M phase

Mitotic phase; includes mitosis and cytokinesis.

Prokaryotic DNA Replication

Starts at the origin (ori) and proceeds bidirectionally toward the termination site (ter).

Steps of Binary Fission

1) DNA replication 2) DNA segregation 3) Cytokinesis, resulting in two identical daughter cells.

Eukaryotic Cell Cycle

Consists of interphase (G1, S, G2) and mitotic phase (M), controlling growth and division.

Restriction Point (G1 → S)

A checkpoint that commits a cell to DNA replication and division.

RB Protein Role

Inhibits cell cycle progression until phosphorylated by active cyclin-CDK complexes.

p21 Function

Inhibits cyclin-CDK activity in response to DNA damage, allowing time for repair.

Reproductive Signals in Cells

Prokaryotes use environmental cues; eukaryotes rely on growth factors and internal signals.

Cell Cycle Checkpoints

G1 checks for size/DNA damage, G2 checks DNA replication, M ensures proper chromosome attachment.

Purpose of Mitosis

To produce two genetically identical diploid daughter cells for growth and repair.

Cytokinesis in Prokaryotes

Occurs after DNA replication and segregation, involves plasma membrane pinching.

Purpose of Meiosis

To produce four genetically diverse haploid gametes for sexual reproduction.

Mitosis Daughter Cells

Genetically identical to the parent cell (barring mutations).

Meiosis Daughter Cells

Genetically distinct due to crossing over and independent assortment.

Eukaryotic DNA Replication

Occurs during S phase of interphase, producing sister chromatids.

Protein kinase

An enzyme that modifies other proteins by adding phosphate groups.

Restriction point (R)

A control point in G1 that determines whether a cell proceeds to S phase.

CDKs

Cyclin-dependent kinases, enzymes that control progression through the cell cycle.

Cyclin

Proteins that regulate the timing of the cell cycle in eukaryotic cells.

Retinoblastoma protein (RB)

A protein that inhibits the cell cycle by preventing progression past the restriction point.

p21

A cell cycle inhibitor that binds to and inhibits CDKs.

Protease

An enzyme that breaks down proteins by hydrolyzing peptide bonds.

Apoptosis

Programmed cell death, a regulated process of cellular self-destruction.

Replication cell cycle checkpoints

Control mechanisms that ensure proper division and repair during the cell cycle.

Growth factors

External signaling molecules that stimulate cell growth and division.

Platelet-derived growth factor

A growth factor that stimulates division in blood vessel cells and fibroblasts.

Erythropoietin

A growth factor that stimulates production of red blood cells.

Interleukins

Growth factors that regulate white blood cell formation and immune responses.

Centromere

The region of a chromosome where the two sister chromatids attach.

Nucleosomes

Bead-like units of DNA wrapped around histone proteins, forming chromatin.

Cohesin

Protein complexes that hold sister chromatids together after DNA replication.

Condensins

Proteins that help condense chromosomes during mitosis and meiosis.