Cell Division, Mitosis, and Meiosis Flashcards

Vocabulary flashcards covering cell division, the cell cycle, mitosis, meiosis, chromosomal abnormalities, and cancer regulation.

Cell Division

The process by which one parent cell produces new cells, which is essential for growth, repair of damaged tissues, replacement of worn-out cells, and reproduction.

Cell Cycle

The ordered sequence of events that prepares a cell for division and results in two daughter cells, divided into Interphase and Mitotic Phase (M Phase).

Interphase

The phase occupying about $90\%$ of the cell cycle during which the cell grows, performs normal functions, duplicates DNA, and prepares for division.

$G_1$ Phase (First Gap)

The subphase of interphase where the cell increases in size, organelles multiply, proteins are synthesized, energy is stored, and normal metabolism is performed.

S Phase (Synthesis)

The subphase of interphase where DNA is replicated, centrosomes duplicate, and every chromosome becomes two identical sister chromatids.

$G_2$ Phase (Second Gap)

The subphase of interphase where the cell continues growing, DNA is checked for errors, and proteins needed for mitosis (such as spindle proteins) are produced.

$G_0$ Phase

A resting stage outside the cell cycle entered by non-dividing cells, such as neurons and cardiac muscle cells.

Karyokinesis

The division of the cell nucleus during the mitotic phase.

Cytokinesis

The division of the cytoplasm that completes cell division to produce two genetically identical daughter cells.

$G_1$ Checkpoint

An internal quality-control checkpoint that checks if the cell is large enough, if nutrients are available, and if DNA is damaged before allowing entry into S phase.

$G_2$ Checkpoint

An internal quality-control checkpoint that verifies whether DNA has been completely copied and is undamaged before entering mitosis.

M Checkpoint (Spindle Checkpoint)

An internal checkpoint that verifies if all chromosomes are attached to spindle fibers correctly before anaphase begins.

Cyclins

Proteins whose concentration rises and falls during the cell cycle to regulate progression through each phase.

Cyclin-Dependent Kinases (CDKs)

Enzymes activated by cyclins that phosphorylate target proteins to push the cell into the next phase of the cell cycle.

Mitosis

Nuclear division that produces two genetically identical diploid ($2n$) daughter cells from body (somatic) cells.

Cleavage Furrow

A groove formed by a contractile ring of actin in animal cells during cytokinesis that pinches the cell into two daughter cells.

Cell Plate

A structure formed from Golgi vesicles in plant cells during cytokinesis that develops into a new cell wall between daughter cells.

Nondisjunction

The failure of sister chromatids to separate properly during mitosis or meiosis, resulting in one daughter cell with an extra chromosome ($n+1$) and one with a missing chromosome ($n-1$).

Down Syndrome (Trisomy 21)

A trisomy disorder where the 21st chromosome has three instead of two chromosomes, often characterized by a short neck with excess skin, flattened facial profile, small head, ears, and mouth, and upward slanting eyes.

Edward Syndrome (Trisomy 18)

A condition caused by an additional copy of chromosome 18, characterized by cleft palate, clenched fists, deformed feet, low-set ears, chest deformity, and severe developmental delays.

Patau Syndrome (Trisomy 13)

A genetic disorder caused by an additional copy of chromosome 13, manifesting as cleft lip or palate, extra fingers or toes (polydactyly), low-set ears, small head, and hernias.

Klinefelter Syndrome ($47, \text{XXY}$)

A condition resulting from two or more X chromosomes in males, primarily characterized by infertility and small, poorly functioning testicles.

Trisomy X Syndrome ($47, \text{XXX}$)

A condition characterized by the presence of an extra X chromosome in each cell of a female, where affected individuals are often taller than normal with mild or no symptoms.

Turner Syndrome ($45, \text{XO}$)

A condition affecting females where one X chromosome is missing or partially missing, physically characterized by a webbed neck, short stature, and swollen hands and feet.

Mosaicism

A genetic situation occurring when a mutation happens during mitosis in an early cell of a developing organism, causing only the cells derived from that mutated cell to carry the mutation.

Cancer

A disease in which cells lose normal control over the cell cycle, allowing them to divide uncontrollably, ignore checkpoints, and avoid cell death.

Mutation

A permanent change in DNA caused by radiation, UV light, cigarette smoke, certain chemicals, viruses, or random DNA replication errors.

Proto-oncogenes

Normal genes that promote cell growth and division and are necessary for normal development.

Oncogenes

Mutated forms of proto-oncogenes that continuously stimulate cell division.

p53 Protein

Known as the 'Guardian of the Genome,' a tumor suppressor protein that stops the cell cycle, activates DNA repair, or initiates apoptosis if repair fails.

p21 Protein

A protein that blocks cyclin-dependent kinases (CDKs), preventing the cell from entering S phase until DNA is repaired.

Tumor Suppressor Genes

Genes that slow or stop the cell cycle, repair DNA, trigger apoptosis, and prevent uncontrolled cell growth (e.g., p53, Rb, p21).

Apoptosis

The controlled, programmed destruction of damaged or unnecessary cells, during which the cell breaks into apoptotic bodies that are safely removed by immune cells.

Benign Tumor

A non-cancerous mass of abnormal cells that does not invade nearby tissues and usually remains localized.

Malignant Tumor

A cancerous mass of abnormal cells that invades nearby tissues and can spread through blood or lymph.

Metastasis

The spread of cancer cells from a primary malignant tumor to other parts of the body.

Meiosis

A two-step cell division process that produces four haploid gametes (sperm or egg cells) from a single diploid cell.

Crossing Over

The process during prophase I of meiosis in which homologous chromosomes trade parts, creating new combinations of alleles.

Synaptonemal Complex

A protein structure that holds homologous chromosomes together during crossing over in prophase I of meiosis.

Chiasmata

Cross-shaped structures visible under a microscope where homologous chromosomes remain linked together after the synaptonemal complex breaks down.