02a- Meiosis: Spermatogenesis & Oogenesis

Genome

All the genetic material of an organism.

Number of autosomes each parent donates

22 autosomes.

Number of sex chromosomes each parent donates

1 sex chromosome (X or Y).

Diploid (2n)

Genome with 2 complete sets of chromosomes (23 pairs).

Haploid (n)

Genome with one complete set of chromosomes (23 total).

Homologous chromosomes

Chromosome pairs that are the same size and contain the same genes (except X and Y).

Sister chromatids

Two identical halves of a duplicated chromosome joined at the centromere.

Somatic cells

Regular body cells, diploid.

Gametes

Reproductive cells (ova and sperm), haploid.

Process that produces gametes

Meiosis.

Centrioles

Organizing centers for spindle fibers during cell division.

Spindle fibers

Protein filaments that move chromosomes during division.

Centromere

Region linking sister chromatids and attaching spindle fibers.

Gene

DNA segment coding for proteins or functional RNA.

Purpose of mitosis

Make more somatic cells for growth.

Outcome of mitosis

One 2n cell divides into two 2n cells.

Phases of mitosis

Prophase, Metaphase, Anaphase, Telophase.

Purpose of meiosis

Make genetically unique gametes for sexual reproduction.

Outcome of meiosis

One 2n cell divides into four n cells.

Phases of meiosis I

Prophase I, Metaphase I, Anaphase I, Telophase I.

Phases of meiosis II

Prophase II, Metaphase II, Anaphase II, Telophase II.

What separates in meiosis I

Homologous chromosomes.

What separates in meiosis II

Sister chromatids.

Prophase I

Synapsis, tetrad formation, crossing over occurs.

Tetrad

Two homologous chromosomes paired together.

Crossing over

Exchange of genetic material between chromatids at chiasmata.

Metaphase I

Tetrads align at metaphase plate; random assortment occurs.

Anaphase I

Homologous chromosomes separate; sister chromatids stay attached.

Telophase I & Cytokinesis

Two haploid cells form.

Prophase II

Nuclear envelope breaks down, chromosomes condense, and spindle fibres form

Metaphase II

Chromosomes align at metaphase plate.

Anaphase II

Sister chromatids separate.

Telophase II & Cytokinesis

Four unique haploid gametes form.

Autosomes

Non-sex determining chromosomes

Allosomes

Sex determining chromosomes

Chiasma

Point where chromatids exchange genetic material during crossing over