Cell Division and Genetics Vocabulary

Vocabulary flashcards covering chromosome structure, meiosis, and chromosomal abnormalities based on the lecture notes.

Somatic Cell

All cells in a multicellular organism except sperm and eggs; they are diploid (e.g., liver cells, brain cells, skin cells).

Gametes

Eggs and sperm; they are haploid.

Autosomes

Chromosomes that do not determine an individual’s sex.

Sex Chromosomes

Chromosomes that determine an individual’s sex.

Homologous Chromosomes

A pair of chromosomes of the same length, banding pattern, centromere position, and containing the same types of genes, with one homolog inherited from the father and the other inherited from the mother.

Diploid

Having both copies of each chromosome; designated as $2n$ (for example, in dogs, $2n = 78$). Somatic cells are diploid, and it also refers to the number of chromosomes a specific species has.

Haploid

Having only one copy of each chromosome; designated as $n$. Gamete cells are haploid.

Sister Chromatids

Identical strands of a chromosome, created by DNA replication during S phase of the cell cycle, that are attached to each other at the centromere.

Centromere

In a duplicated chromosome, the region where sister chromatids are joined to each other and the site where the kinetochore forms.

Kinetochore

Proteins that attach to chromosomes at the centromere, linking each chromosome to the mitotic spindle.

Centrosomes

Microtubule-organizing structures that function in mitosis/meiosis to move chromosomes in the cell.

Metaphase Plate

The plane through the center of a cell where chromosomes are aligned during Metaphase of mitosis/meiosis.

Synapsis

Process occurring during Prophase I of Meiosis I, when replicated homologous chromosomes pair up and physically connect to each other to form tetrads.

Crossing Over

The exchange of genetic material between non-sister chromatids during Prophase I of meiosis.

Chiasma

The physical location where crossing over occurs. Each pair of homologous chromosomes has at least one chiasma, and most have several (called chiasmata).

Recombinant Chromosome

A chromosome that has undergone crossing over and now contains genetic information from both parents.

Law of Independent Assortment

States that tetrad (and their associated genes) assort independently along the metaphase plate during Meiosis I.

Nondisjunction

An error in Meiosis (which can also occur in Mitosis) in which homologous chromosomes are not separated during Meiosis I and/or sister chromatids are not separated during Meiosis II, resulting in gametes with an incorrect number of chromosomes.

Aneuploidy

An aberrant chromosome number in gametes; can have extra or missing chromosomes.

Monoploidy

A type of aneuploidy characterized by missing one chromosome of a homologous pair (e.g., Turner’s Syndrome, in which females have only one X chromosome).

Polyploidy

A type of aneuploidy characterized by having an extra chromosome within a homologous pair (e.g., Down Syndrome, which has three copies of chromosome 21).