Cell Cycle and Cell Division

Flashcards covering key terms and definitions on cell division, mitosis, interphase, and meiosis based on the General Zoology lecture.

Cell Division

The process by which new cells are produced from pre-existing cells for growth and to replace damaged or old cells.

DNA Replication

The copying of DNA prior to cell division, ensuring each new cell receives an identical copy of the DNA molecules.

Interphase

The phase of the cell cycle comprising the $G_1$, $S$, and $G_2$ stages during which the cell grows, copies its DNA, and prepares for division.

$G_1$ Stage

The primary growth stage of interphase following cell division, where cells mature by producing cytoplasm and organelles while carrying out normal metabolic activities.

$S$ Stage

The synthesis phase of interphase during which DNA is copied or replicated.

$G_2$ Stage

The secondary growth stage of interphase occurring after DNA replication, during which organelles, proteins, and structures needed for cell division (such as centrioles) are synthesized.

Mitosis

The division of the cell nucleus (karyokinesis) in eukaryotic cells, consisting of four stages: prophase, metaphase, anaphase, and telophase.

Karyokinesis

Another term for nuclear division during eukaryotic cell division.

Prophase

The first stage of mitosis, characterized by chromatin condensing into visible chromosomes, breakdown of the nuclear envelope and nucleolus, and formation of the mitotic spindle.

Kinetochores

Spindle fibers that attach to the centromere of each chromosome to guide chromosome movement during cell division.

Polar Fibers

Spindle fibers that extend across the cell from one pole to the opposite pole.

Asters

Short spindle fibers radiating outward from centrioles at the poles of animal cells.

Metaphase

The stage of mitosis where chromosomes attached to kinetochore fibers move to and line up along the equator (metaphase plate) of the cell.

Anaphase

The rapid stage of mitosis in which centromeres divide and sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers.

Telophase

The final stage of mitosis where sister chromatids reach opposite poles, nuclear envelopes re-form, nucleoli reappear, spindle disassembles, and chromosomes decondense back into chromatin.

Cytokinesis

The division of the cytoplasm that separates the parent cell into two identical daughter cells.

Cell Plate

The structure formed across the cell equator during cytokinesis in plant cells to divide the cytoplasm.

Cleavage Furrow

The shallow groove formed at the equator of an animal cell during cytokinesis that pinches the cell into two separate daughter cells.

Oncogenes

Special proteins that increase the likelihood of a normal cell developing into a cancerous tumor cell when cell division is uncontrolled.

Meiosis

A reduction-division cell process consisting of two nuclear divisions that reduces the chromosome number by half (from diploid $2n$ to haploid $1n$) to form four daughter gametes or spores.

Synapsis

The pairing up of homologous chromosomes during Prophase I of meiosis.

Bivalent

A unit formed by each synapsed pair of homologous chromosomes during Prophase I of meiosis.

Tetrad

A structure consisting of two pairs of sister chromatids (four chromatids total) formed when homologous chromosomes condense during Prophase I.

Chiasma

The point or region where non-sister chromatids of homologous chromosomes intertwine and stay in contact during crossing over.

Crossing Over

The exchange of genetic material between non-sister chromatids of homologous chromosomes during Prophase I of meiosis, creating genetic variation.

Terminalization

The late stage of Prophase I where the nucleolus and nuclear envelope break down and the centromeres of each tetrad attach to the newly formed spindle fibers.

Nondisjunction

An error during meiotic division where homologous chromosomes or sister chromatids fail to separate properly.

Spermatogenesis

The meiotic process of male gamete (sperm) production occurring in the testes.

Oogenesis

The meiotic process of female gamete (ova or egg cell) production occurring in the ovaries.

Spermiogenesis

The developmental phase where round haploid spermatids undergo morphological differentiation to become motile spermatozoa.

Polar Body

A small non-functional cell containing minimal cytoplasm pinched off during the meiotic divisions of oogenesis.