Cell Cycle, Mitosis, and Meiosis

Vocabulary practice flashcards covering cell cycle phases, checkpoints, mitosis, cytokinesis, regulation mechanisms, and meiosis based on the lecture notes.

Binary fission

A simpler form of asexual cell division in prokaryotes (such as E. coli) where a single bacterial chromosome replicates, the two copies move apart, and the cell divides into two identical daughter cells.

$G_0$ phase

A resting, non-dividing state entered by cells that do not receive a go-ahead signal at the $G_1$ checkpoint, characteristic of mature nerve and muscle cells.

Satellite stem cells

Specialized stem cells that divide to repair minor muscle damage since mature muscle cells do not divide.

Interphase

The longest, non-dividing stage of the cell cycle consisting of $G_1$, S, and $G_2$ phases, during which the cell grows, duplicates its DNA, and synthesizes division structures.

Gap 1 ($G_1$) phase

The first growth phase of interphase where the cell grows rapidly, performs routine metabolic functions, and replicates organelles.

Synthesis (S) phase

The phase of interphase where the cell's DNA is copied, resulting in chromosomes that each consist of two sister chromatids attached at a centromere.

Gap 2 ($G_2$) phase

The second growth phase of interphase characterized by additional cellular growth and the assembly of hollow microtubules needed for mitosis.

Sister chromatids

Two identical copies of a duplicated chromosome connected together at a specialized region called the centromere.

Mitosis

The division of the cell nucleus into two identical daughter nuclei, each retaining the exact same chromosome number as the original parent cell.

Prophase

The first stage of mitosis during which chromatin condenses into chromosomes, centrioles move to opposite ends, spindle fibers form, and the nuclear envelope breaks down.

Metaphase

The second stage of mitosis where duplicated chromosomes line up in the middle (equatorial plate) of the cell, attached to spindle fibers by their centromeres.

Anaphase

The third stage of mitosis where centromeres split and sister chromatids separate into individual chromosomes, moving toward opposite poles as the cell elongates.

Telophase

The final stage of mitosis during which separated chromosomes reach opposite poles, uncoil, and a new nuclear envelope reforms around each group of chromosomes.

Cytokinesis

The final stage of the cell cycle where the cytoplasm divides, splitting the parent cell into two daughter cells.

Cleavage furrow

A shallow groove formed by the pinching inward of the animal cell membrane during cytokinesis to divide the cytoplasm.

Cell plate

A structure formed along the center of a dividing plant cell by coalescing vesicles that develops into a new cell membrane and cell wall.

$G_1$ checkpoint

A regulatory checkpoint near the end of $G_1$ that determines whether a cell will divide or enter $G_0$ based on cell size, health, and environmental factors.

$G_2$ checkpoint

A checkpoint near the end of $G_2$ that uses repair enzymes to verify that DNA replication was completed successfully before allowing entry into mitosis.

M checkpoint

A checkpoint during metaphase that monitors chromosome alignment and attachment to spindle fibers before permitting sister chromatid separation in anaphase.

Cyclin-dependent kinases (CDKs)

Regulatory protein kinases that require association with cyclins to become activated and phosphorylate target proteins driving cell cycle progression.

Maturation promoting factor (MPF)

A cyclin-CDK complex whose activity peaks in metaphase, promoting mitosis by phosphorylating proteins and driving the cell past the $G_2$ checkpoint.

Retinoblastoma (Rb) protein

A transcription-factor inhibitor at the $G_1$ checkpoint that halts the cell cycle by binding the transcription factor E2F when CDK levels are low.

p53 protein

A transcription factor at the $G_1$ checkpoint that halts the cell cycle to allow DNA repair or triggers cell suicide if damage is severe; missing or mutated in approximately 50% of cancer sufferers.

Cancer

A disease characterized by the uncontrolled growth and proliferation of cells, often resulting from checkpoint failures or mutations.

Meiosis

A two-division form of cell division occurring in germ cells that reduces the chromosome number by half, yielding four unique haploid daughter cells.

Oogenesis

The process of meiosis in females that produces one viable ovum and three degenerating polar bodies.

Crossing-over

The exchange of genetic material between homologous chromosomes that occurs during prophase 1 of meiosis, contributing to genetic variation.

Zygote

A single diploid cell ($2n$) produced by the fusion of two haploid gametes during fertilization.