The Eukaryotic Cell Cycle, Mitosis, and Meiosis

Flashcards covering the themes of the eukaryotic cell cycle, the specific phases of mitosis, the regulatory checkpoints, and the processes unique to meiosis produced from the BIO 2000 Lecture 17 notes.

Eukaryotic Cell Cycle

A highly regulated series of events involving repeated rounds of cell growth and division.

Cytogenetics

The field of genetics involving the microscopic examination of chromosomes and cell division.

Karyotype

An image that reveals the number, size, and form of chromosomes in an actively dividing cell.

Autosomes

The $22$ pairs of chromosomes in humans that are not sex chromosomes.

Sex chromosomes

The single pair of chromosomes in humans ($XX$ or $XY$) that determine an individual's sex.

Diploid ($2n$)

Reference to a cell or organism containing two sets of chromosomes; human cells have $23$ pairs.

Haploid ($1n$)

Reference to a cell containing one member of each chromosome pair; human gametes have $23$ total chromosomes.

Homologs

Members of a pair of chromosomes in diploid species that are nearly identical in size and genetic composition.

Interphase

The phase of the cell cycle including $G_1$, $S$, and $G_2$ during which chromosomes are decondensed and found in the nucleus.

$G_1$ phase

The first gap phase where cell growth occurs and molecular changes may promote progression through the cell cycle.

Restriction point ($G_1$ checkpoint)

A point in the $G_1$ phase where the cell becomes committed to entering the $S$ phase and replicating DNA.

$S$ phase

The phase in which chromosomes replicate to form sister chromatids.

Sister chromatids

Two identical copies of a chromosome that stay joined to each other after replication.

$G_2$ phase

The second gap phase where the cell synthesizes proteins needed for mitosis and cytokinesis.

Mitosis

The division of one cell nucleus into two, involving the separation of sister chromatids.

Cytokinesis

The process that follows mitosis to divide the cytoplasm into two daughter cells.

Cyclins

Proteins whose levels vary throughout the cell cycle and are responsible for advancing the cell through its phases.

Cyclin-dependent kinases (cdks)

Kinases that control the cell cycle and must bind to a cyclin to be active.

$G_2$ Checkpoint

A regulatory point that checks for DNA damage, ensures all DNA is replicated, and monitors protein levels for the $M$ phase.

Metaphase Checkpoint

A regulatory point that determines if all chromosomes are attached to the spindle apparatus.

Centromere

The region where sister chromatids are tightly associated and serves as the attachment site for the kinetochore.

Kinetochore

A protein structure at the centromere used for sorting chromosomes.

Mitotic spindle apparatus

A structure composed of microtubules responsible for organizing and sorting the chromosomes during mitosis.

Centrosomes

Microtubule organizing centers ($MTOCs$) that define the poles and duplicate at the beginning of the $M$ phase.

Astral microtubules

Microtubules that position the mitotic spindle within the cell.

Polar microtubules

Microtubules that function to separate the two poles of the cell.

Kinetochore microtubules

Microtubules attached to the kinetochores bound to the centromeres of the sister chromatids.

Prophase

The stage of mitosis where chromosomes condense, the nuclear membrane dissociates into vesicles, and the nucleolus is no longer visible.

Prometaphase

The stage of mitosis where the nuclear envelope completely fragments and the mitotic spindle is fully formed.

Metaphase

The stage of mitosis where pairs of sister chromatids are aligned in a single row along the metaphase plate.

Anaphase

The stage of mitosis where sister chromatid connections break and individual chromosomes move toward opposite poles as kinetochore microtubules shorten.

Telophase

The stage of mitosis where chromosomes reach their respective poles, decondense, and nuclear membranes re-form.

Cleavage furrow

A structure in animal cells that constricts like a drawstring to separate the cells during cytokinesis.

Cell plate

A structure in plant cells that forms a cell wall between the two daughter cells during cytokinesis.

Meiosis

The process by which haploid cells are produced from a cell that was originally diploid, involving two rounds of division.

Bivalent (Tetrad)

A structure formed during synapsis consisting of homologous pairs of sister chromatids lying side by side.

Synapsis

The process of homologous pairs of sister chromatids associating with each other.

Synaptonemal complex

A protein structure that connects homologous chromosomes during synapsis, though its function is uncertain.

Crossing over

The physical exchange between chromosome pieces of a bivalent that may increase genetic variation.

Chiasma

The site where the arms of the chromosomes remain adhered following crossing over.