Cell Division and Cell Cycle

Vocabulary flashcards covering fundamental terms related to cell division, the cell cycle, and their regulation, as presented in the lecture notes.

Cell Division

The process by which a parent cell reproduces to form new cells; key to reproduction, growth, development, and tissue renewal.

Cell Cycle

Ordered sequence of events in a cell’s life, consisting of Interphase (G₁, S, G₂) and the Mitotic (M) phase.

Binary Fission

Asexual cell division in prokaryotes that produces two genetically identical daughter cells through DNA replication, chromosome segregation, and cytokinesis.

Mitosis

Eukaryotic nuclear division producing two diploid daughter cells identical to the parent; stages: prophase, prometaphase, metaphase, anaphase, telophase.

Meiosis

Eukaryotic cell division in reproductive organs yielding four haploid gametes with half the parental chromosome number; involves Meiosis I and Meiosis II.

Prokaryotic Cell

Unicellular organism without a membrane-bound nucleus; reproduces asexually, commonly by binary fission.

Eukaryotic Cell

Cell with membrane-bound organelles and nucleus; divides by mitosis or meiosis.

Genome

The complete set of a cell’s DNA, containing its genetic information.

Chromosome

A DNA molecule tightly packaged with proteins; vehicle of heredity found in cell nuclei.

Chromatin

DNA-protein complex that forms chromosomes; allows long DNA strands to condense inside the nucleus.

Chromatid

One of two identical DNA copies of a duplicated chromosome, joined to its sister at a centromere.

Sister Chromatids

The pair of identical chromatids formed after DNA replication, later separated during cell division.

Diploid (2n)

Describes cells with two complete sets of chromosomes (e.g., human somatic cells: 46).

Haploid (n)

Describes cells with one set of chromosomes (e.g., human gametes: 23).

Somatic Cell

Any body cell excluding gametes; undergoes mitosis and is diploid in humans.

Gamete

Reproductive cell (sperm or egg) produced by meiosis; haploid in chromosome number.

Pilus

Surface appendage of prokaryotes that aids in attachment or DNA transfer.

Capsule

Sticky outer layer of some prokaryotes providing protection and adherence.

Cell Wall

Rigid structure outside the plasma membrane in bacteria, plants, fungi, providing shape and support.

Plasma Membrane

Phospholipid bilayer enclosing the cytoplasm, regulating substance passage.

Nucleoid

Region in prokaryotes where circular DNA is located; lacks a nuclear envelope.

Cytoplasm

Cell’s interior fluid containing organelles (in eukaryotes) or ribosomes (in prokaryotes).

Ribosome

Organelle composed of rRNA and proteins; site of protein synthesis.

Flagellum

Long whip-like structure enabling cellular motility in many bacteria and some eukaryotes.

Interphase

Longest phase of cell cycle encompassing G₁, S, and G₂; cell grows, duplicates DNA, prepares for division.

G₁ Phase

First ‘gap’ of interphase; intense growth, organelle formation, enzyme synthesis, first checkpoint.

S Phase

Interphase substage where DNA replication and microtubule protein production occur.

G₂ Phase

Second growth phase; cell enlarges, synthesizes proteins, passes critical G₂ checkpoint before mitosis.

G₀ Phase

Quiescent state where cells exit the cycle and perform normal functions without dividing (e.g., neurons).

Prophase

First mitotic stage; chromatin condenses, nucleoli disappear, mitotic spindle begins to form.

Prometaphase

Mitotic stage when nuclear envelope fragments, kinetochores form, spindle attaches to chromosomes.

Metaphase

Mitotic stage where chromosomes align at the metaphase plate; kinetochores connected to opposite poles.

Anaphase

Stage where cohesin is cleaved, sister chromatids separate and move toward opposite poles; cell elongates.

Telophase

Final mitotic stage; nuclear envelopes reform, chromosomes decondense, spindle disassembles.

Cytokinesis

Division of cytoplasm producing two separate cells; involves cleavage furrow in animals, cell plate in plants.

Cleavage Furrow

Indentation produced by contractile ring of microfilaments during animal-cell cytokinesis.

Cell Plate

Structure formed by vesicle fusion during plant cytokinesis that becomes the new cell wall.

Centrosome

Microtubule-organizing center containing centrioles in animal cells; duplicates before mitosis.

Aster

Star-shaped array of short microtubules radiating from centrosomes during mitosis.

Kinetochore

Protein complex at centromere where spindle microtubules attach during division.

Microtubules

Cytoskeletal filaments forming the mitotic spindle and contributing to cell shape and transport.

Kinase

Enzyme that transfers phosphate groups, regulating activity of target molecules; pivotal in cell-cycle control.

Cyclin

Regulatory protein whose concentration cycles; binds CDKs to activate cell-cycle progression.

Cyclin-Dependent Kinase (CDK)

Kinase activated by cyclin binding; drives transitions through cell-cycle phases.

Checkpoint

Control point in cell cycle (G₁, G₂, spindle/M) ensuring conditions are met before progression.

Maturation-Promoting Factor (MPF)

Cyclin B–CDK1 complex that triggers the cell’s passage from G₂ into mitosis.

Growth Factor

External signaling molecule that stimulates cell division.

Contact Inhibition

Phenomenon where cell division stops when cells touch their neighbors; lost in cancer cells.

Cadherins

Cell-adhesion proteins important for maintaining contact inhibition; mutations can promote uncontrolled growth.

Apoptosis

Programmed cell death eliminating damaged, unused, or dangerous cells.

Tumor

Disorganized mass of cells with uncontrolled division.

Benign Tumor

Localized, non-invasive tumor that may be removed surgically.

Malignant Tumor

Tumor with cells that invade tissues and can metastasize to distant sites.

Metastasis

Spread of cancer cells from original tumor to form secondary tumors in other body parts.