Cell Cycle, Mitosis, and Meiosis

Vocabulary flashcards covering the key terms, phases, mechanisms, and regulatory checkpoints of the cell cycle, mitosis, and meiosis from Chapters 12 and 13.

Mitosis

The process of splitting the cell nucleus.

Cytokinesis

The process of splitting the cell cytoplasm.

Genome

All of a cell's genetic information (DNA); in humans, this consists of 46 chromosomes (23 pairs).

Sister Chromatids

Replicated chromosomes that are joined together at a region known as the centromere.

Centromere

The specific region where replicated chromosomes (sister chromatids) are joined together.

Interphase

The portion of the cell cycle taking up 90% of cycle time, consisting of $G_1$, $S$, and $G_2$ phases.

$G_1$ Phase (Gap 1)

The stage of interphase where the cell grows and performs normal metabolic activity.

$S$ Phase (Synthesis)

The stage of interphase during which DNA is replicated and chromosomes are duplicated.

$G_2$ Phase (Gap 2)

The stage of interphase where the cell continues to grow and prepares for cell division.

M Phase (Mitotic Phase)

The phase of the cell cycle that includes mitosis and cytokinesis.

Prophase (Mitosis)

The phase of mitosis in which chromatin condenses into visible chromosomes, the mitotic spindle begins to form, and nucleoli disappear.

Prometaphase

The mitotic phase where the nuclear envelope fragments/dissolves and spindle microtubules attach to chromosome kinetochores.

Metaphase (Mitosis)

The phase of mitosis where chromosomes align single-file down the middle of the cell at the metaphase plate.

Anaphase (Mitosis)

The mitotic phase where sister chromatids separate into individual daughter chromosomes and migrate toward opposite poles via motor proteins and microtubule shortening.

Cleavage Furrow

The groove formed during animal cell cytokinesis produced by a contractile ring of microfilaments to pinch the cell into two.

Cell Plate

A structure formed in plant cells during cytokinesis by fusing vesicles that ultimately constructs a new cell wall.

$G_1$ Checkpoint

The 'restriction point' of the cell cycle; if a cell does not receive the go-ahead signal here, it enters the non-dividing resting state $G_0$.

$G_0$ Phase

A non-dividing resting state entered by cells that do not pass the $G_1$ checkpoint.

$M$ Checkpoint

A critical regulatory checkpoint that halts cell division if chromosomes are not properly attached to the spindle.

Cyclins and Cyclin-dependent Kinases (Cdks)

Molecular regulators that combine to form active complexes (such as MPF at the $G_2$ checkpoint) to drive the cell into mitosis.

Density-dependent Inhibition

A regulatory phenomenon exhibited by normal cells in which they cease dividing when crowded.

Anchorage Dependence

The requirement that normal cells must be attached to a substratum or surface in order to divide.

Necrosis

Unregulated, messy cell death resulting in inflammation.

Apoptosis

Programmed, clean cell death where a cell is digested from within by caspase enzymes, characterized by membrane blebbing and DNA fragmentation.

Heredity

The transmission of traits from one generation to the next.

Gene

A specific sequence of DNA.

Locus

The specific physical location of a gene along the length of a chromosome.

Karyotype

A visual display or arrangement of all the chromosomes within a cell.

Homologous Chromosomes

A pair of matching chromosomes (one inherited from each parent) that carry genes controlling the same inherited characters.

Autosomes

Non-sex chromosomes; humans possess 22 pairs of them.

Sex Chromosomes

The pair of chromosomes responsible for determining biological sex ($XX$ in human females and $XY$ in human males).

Diploid ($2n$)

Cells containing two full sets of chromosomes (e.g., human somatic cells having 46 chromosomes).

Haploid ($n$)

Cells containing a single set of chromosomes (e.g., human gametes having 23 chromosomes).

Synapsis

The pairing up of homologous chromosomes to form tetrads during Prophase I of meiosis.

Chiasmata

The X-shaped microscopic points where crossing over occurs between non-sister chromatids.

Crossing Over

The genetic exchange occurring in Prophase I that breaks and swaps segments of maternal and paternal chromatids to produce novel gene combinations.

Independent Assortment

The random orientation of homologous pairs at the metaphase plate during Metaphase I, providing a 50/50 orientation chance and $2^n$ potential combinations.

Nondisjunction

The failure of homologous chromosomes (in Anaphase I) or sister chromatids (in Anaphase II) to separate properly during cell division.

Aneuploidy

A condition resulting from nondisjunction characterized by an abnormal number of chromosomes in gametes (such as $n + 1$ or $n - 1$).

Down Syndrome

An aneuploid condition also known as Trisomy 21, resulting from having three copies of chromosome 21.