phases and processes of meiosis

biology at SPSV 2024-2025 school year

Interphase

G1, S, G2

Prophase 1

Each replicated chromosome pairs up with its corresponding homologous chromosome. Crossing-over results increase genetic variation.

Metaphase 1

Spindle forms and attaches to each tetrad. Paired homologous chromosomes line up across the center of the cell.

Anaphase 1

Homologous pairs of chromosomes separate. Each pair of spindle fibers pulls one homologous chromosome towards a centriole.

Telophase 1

The separated chromosomes are at opposite ends of the cell. The cell begins to pinch in the middle and the nuclear membrane begins to form again around each cluster of chromosomes.

Cytokinesis (after Telophase 1)

The cell separates into two haploid daughter cells.

Prophase 2

Nuclear membrane dissolves and chromosomes become visible again.

Metaphase 2

Chromosomes line up in the middle and the spindle fibers connect to the centrosomes.

Anaphase 2

Sister chromatids split apart and go to opposite ends of the cell.

Telophase 2

The two cells begin to pinch and the nuclear envelope begins to reform around the chromosome clusters.

Cytokinesis (after Telophase 2)

Separates the two cells into four haploid cells.

Products of meiosis 1

Two haploid cells.

Products of meiosis 2

Four haploid cells.

Meiosis

Process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell. Early step in sexual reproduction. One diploid cell becomes four haploid cells.

Meiosis 1

Genetic material switches and two haploid daughter cells are formed.

Meiosis 2

Four haploid daughter cells are formed.

Mitosis

Form of asexual reproduction. Each daughter cell receives one complete set of chromosomes. Not big genetic diversity.

Crossing over

Tetrad switches legs of chromosomes at the chiasmata.

When does crossing over happen?

Happens in Prophase 1. NOT PROPHASE 2.

Benefits of crossing over

Increases genetic variety.

Genetic variation

When haploid sex cells combine, the number of combinations is many, allowing for lots of genetic variation.

Independent assortment

Independent assortment is how genes independently separate from one another when reproductive cells develop.

Haploid

Term used to refer to a cell that contains only a single set of genes (N).

Diploid

Term used to refer to a cell that contains two sets of homologous chromosomes. (2N)

Fertilization

The process by which male and female gametes (sex cells) are fused together.

Homologous chromosomes

Set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization.