Cell Division: Mitosis and Meiosis

Comprehensive vocabulary flashcards covering the stages of mitosis, meiosis, cell cycle checkpoints, and genetic terminology as presented in the lecture notes.

Somatic cells

Non-reproductive body cells in eukaryotic organisms that undergo mitosis.

Gametes

Sex cells (also known as germline cells) such as sperm and egg that are produced through meiosis.

Checkpoints

Regulatory stages that determine whether the cell cycle proceeds or is halted by checking for errors in replication, growth, or division.

G1 Checkpoint

The primary decision point at the G1/S transition where a cell chooses whether or not to divide based on cell size, nutrients, growth factors, and DNA damage.

G2 Checkpoint

A checkpoint at the G2/M transition that checks for DNA damage and DNA replication completeness before entering M phase.

Apoptosis

Programmed cell death which may occur if DNA damage is detected at the G2 checkpoint and is found to be irreparable.

M Checkpoint

Also called the Spindle Checkpoint, this occurs during the transition from metaphase to anaphase to ensure all sister chromatids are correctly attached to spindle microtubules.

Mitosis

The division of somatic cells where a single cell divides into two identical daughter cells with the same number of chromosomes as the parent cell.

Chromatin

The extended, uncondensed form of DNA molecules present when the cell is not dividing, allowing for replication and transcription.

Chromosomes

Condensed DNA molecules formed prior to division, where each chromosome consists of a single molecule of DNA.

Prophase (Mitosis)

The first sub-phase of mitosis characterized by three major events: chromosomes condense, spindle fibers form from centrioles, and chromosomes are captured by the spindle.

Metaphase (Mitosis)

The second sub-phase of mitosis where chromosomes align along the equator of the cell with one chromatid facing each pole.

Anaphase (Mitosis)

The third sub-phase of mitosis where sister chromatids separate as spindle fibers attached to kinetochores shorten and pull them towards the poles.

Telophase (Mitosis)

The final sub-phase where spindle fibers disintegrate, nuclear envelopes form around groups of chromosomes, and chromosomes revert to their extended state.

Cytokinesis (Animal vs. Plant)

In animal cells, it occurs through a cleavage furrow created by a ring of microtubules; in plant cells, it occurs through the formation of a cell plate.

Meiosis

A form of cell division that produces four unique haploid daughter cells from a single germ cell, occurring only in the gonads.

Haploid

A cell condition containing half the number of chromosomes ($n$) compared to the parent cell.

Fertilization

The fusion of a sperm ($n=23$) and egg ($n=23$) to form a zygote ($2n=46$).

Synapsis

The process in Prophase I where homologous chromosomes come together to form a tetrad.

Tetrad

A structure formed during Prophase I consisting of two homologous chromosomes or four chromatids (sister and nonsister).

Homologous Chromosomes

A pair of maternal and paternal chromosomes that are similar in shape and size and carry genes controlling the same inherited traits at the same loci.

Crossing Over

The process where segments of nonsister chromatids break and reattach to the other chromatid at sites called chiasmata, resulting in genetic variation.

Karyotype

A method of organizing the chromosomes of a cell based on number, size, and type.

Autosomes

In humans, these are chromosome sets $1$ through $22$ which code for most of the offspring's traits.

Sex Chromosomes

The $23\text{rd}$ set of chromosomes ($XX$ for female, $XY$ for male) that determine the sex of the offspring.

Independent Assortment

The random orientation of homologous pairs to the poles during Metaphase I, calculated by the formula $2^n$ combinations.

Anaphase I

The stage of meiosis where homologous chromosomes separate and move towards opposite poles while sister chromatids remain attached at their centromeres.

Meiosis II

The second round of meiotic division, which is similar to mitosis, where sister chromatids are separated to produce four haploid gametes.