Meiosis - Key Vocabulary (Advanced Animal Science)

Vocabulary flashcards covering key terms and definitions from the meiosis lecture notes.

Meiosis

A type of cell division that reduces the chromosome number by half, producing four haploid gametes from one germ cell; occurs in gonads (testes/ovaries in animals; ovary and anther in plants).

Germ cell

A reproductive cell that divides by meiosis to form gametes; located in the gonads.

Gamete

A haploid reproductive cell (sperm or egg) produced by meiosis that fuses with another gamete during fertilization.

Haploid

A cell containing a single set of chromosomes (n); gametes are haploid.

Diploid

A cell containing two complete sets of chromosomes (2n); somatic/body cells are diploid.

Homologous chromosomes

Pairs of chromosomes similar in shape and size that carry the same genes at the same loci; one from each parent.

Locus

The specific location of a gene on a chromosome.

Karyotype

An image or map of an organism’s chromosomes used to study number, size, and structure, including sex chromosomes.

Paternal chromosome

The chromosome that comes from the father in a homologous pair.

Maternal chromosome

The chromosome that comes from the mother in a homologous pair.

Prophase I

The longest stage of meiosis I; chromosomes condense and synapsis occurs to form tetrads.

Synapsis

The pairing of homologous chromosomes during prophase I to form a tetrad.

Tetrad

A group of four chromatids formed when homologous chromosomes pair during prophase I.

Crossing over

Exchange of genetic material between nonsister chromatids in a tetrad, creating genetic variation.

Nonsister chromatids

Chromatids from homologous chromosomes that are not sister chromatids; participate in crossing over.

Chiasma

The site where crossing over occurs between nonsister chromatids.

Metaphase I

Paired homologous chromosomes align at the middle; independent assortment occurs, orienting toward opposite poles.

Independent assortment

Random orientation of homologous chromosome pairs during metaphase I, increasing genetic variation.

Anaphase I

Homologous chromosomes separate and move toward opposite poles; sister chromatids remain attached.

Telophase I

Two haploid sets of chromosomes at opposite poles; cytokinesis yields two haploid daughter cells (chromosomes still doubled).

Meiosis II

Second meiotic division; no interphase (no DNA replication); resembles mitosis with Prophase II, Metaphase II, Anaphase II, Telophase II.

Prophase II

First stage of meiosis II; chromosomes condense again.

Metaphase II

Chromosomes align at the equator with sister chromatids ready to separate.

Anaphase II

Sister chromatids separate and move to opposite poles.

Telophase II

Nuclei reform around separated chromatids; cytokinesis divides into four haploid gametes.

Spermatogenesis

Male gamete formation; typically four sperm cells develop from each germ cell.

Oogenesis

Female gamete formation; cytokinesis is uneven, producing one large ovum and three polar bodies.

Polar body

Small cells formed during oogenesis that usually degenerate, discarding extra chromosomes.

Zygote

Fertilized egg formed by the fusion of sperm and egg; diploid (2n).

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate during meiosis, producing gametes with abnormal chromosome numbers.

Nondisjunction in meiosis I

Homologous chromosomes fail to separate, yielding gametes with n+1 or n−1 chromosomes.

Nondisjunction in meiosis II

Sister chromatids fail to separate, yielding gametes with abnormal chromosome numbers (n+1 or n−1).

Human chromosome number (somatic vs gametes)

Humans have 2n = 46 in somatic cells and n = 23 in gametes.

Sperm cell

Male gamete; haploid cell that fertilizes the egg.

Egg cell (ovum)

Female gamete; large haploid cell formed during oogenesis.

Anther

Pollen-producing part of a flower where plant meiosis occurs to produce pollen.

Ovary

The organ (in plants and animals) that contains the ovules or ova; site of meiosis to produce eggs in animals or ovules in plants.