Lecture 17: Mitosis and the Cell Cycle

Vocabulary practice flashcards covering genome organization, ploidy, chromosome structure, the eukaryotic cell cycle, and the stages of mitosis and cytokinesis.

Genome

All the genetic information ($\text{DNA}$) of an organism or of an individual cell.

Chromosome

A cellular structure in eukaryotes consisting of a long molecule of double-stranded $\text{DNA}$ located in the nucleus.

Sister Chromatids

Two identical copies of a duplicated chromosome produced during $\text{DNA}$ replication, joined together at the centromere.

Centromere

The specialized region of a chromosome where two sister chromatids are joined and where microtubules attach to move chromosomes during cell division.

Ploidy

The number of complete sets or copies of the genome present in a cell.

Diploid ($2n$)

A cell or organism carrying two complete copies of the genome (e.g., in humans, $2n = 46$).

Haploid ($n$)

A cell containing a single set of unique chromosomes (e.g., in human gametes, $n = 23$).

Homologous Chromosomes

A pair of chromosomes (one maternal and one paternal) that possess the same genes at the same locations, though they may carry different alleles.

Alleles

Different variants or alternative versions of the same gene.

Zygote

A single diploid ($2n = 46$) cell resulting from the fusion of gametes (fertilization), which divides by mitosis to form a multicellular adult containing approximately $10^{14}$ cells.

Centrosome

A cellular structure that organizes microtubules and assists in moving chromosomes during division; it divides during interphase.

Interphase

The extended period of the cell cycle between divisions where the cell carries out metabolic activity, growth, and chromosome duplication; consists of $G_1$, S, and $G_2$ phases.

$G_1$ Phase

The first gap phase of interphase characterized by active metabolic activity and cell growth before $\text{DNA}$ synthesis begins.

S Phase

The synthesis phase of interphase characterized by metabolic activity, cellular growth, and $\text{DNA}$ replication (synthesis).

$G_2$ Phase

The second gap phase of interphase involving continued metabolic activity, cell growth, and final preparation for cell division.

Mitosis

The process of cell division in which one parent cell duplicates its $\text{DNA}$ and undergoes a single nuclear division to produce two daughter cells with the exact same chromosome number.

Meiosis

A specialized division process used for gamete production that reduces the chromosome number by half, yielding four haploid ($n$) cells from a diploid ($2n$) parent cell through two successive divisions.

Prophase

The first phase of mitosis during which chromatin condenses into visible chromosomes of joined sister chromatids, the nuclear envelope breaks down, and centrosomes migrate apart to form the mitotic spindle.

Metaphase

The mitotic phase during which duplicated chromosomes reach maximum condensation and align individually along the equatorial plane (metaphase plate).

Anaphase

The phase of mitosis in which centromeres divide and sister chromatids separate into daughter chromosomes that are pulled to opposite poles of the cell.

Telophase

The final stage of mitosis during which daughter chromosomes reach the poles, $\text{DNA}$ decondenses, and nuclear envelopes reform around each set of chromosomes.

Cytokinesis

The division of the cytoplasm following mitosis that yields two distinct daughter cells.

Cleavage Furrow

A shallow groove formed near the cell equator during animal cell cytokinesis by a contractile ring of microfilaments that pinches the cell into two daughter cells.

Cell Plate

A membrane-bounded, flattened sac that forms across the middle of a dividing plant cell by the fusion of vesicles, ultimately giving rise to a new cell wall between the daughter cells.