Mitosis and Meiosis

There are two types of cell divisions, mitosis and meiosis.

Mitosis is a process in which two exactly the same cells are reproduced from one.

Meiosis involves two cell divisions that give rise to four gametes (sex cells), each possessing half the number of chromosomes in the original cell.

Mitosis and meiosis are similar in some stages.

Interphase: Interphase (G1 and G2)

Chromosomes are not easily visible because they are uncoiled.

Prophase:

The chromosomes begin to coil.

The spindle apparatus begins to form as centrosomes move apart.

Prometaphase:

The nuclear membrane disintegrates.

Kinetochores form on the chromosomes.

Kinetochore microtubules attach to the chromosomes.

Metaphase:

The chromosomes become aligned on a plane.

Anaphase:

The chromatids separate (The number of chromosomes doubles).

Telophase:

The nuclear membrane reappears.

The chromosomes uncoil.

The spindle apparatus breaks down.

The cell divides into two.

Meiosis

Prophase I

Homologous chromosomes become paired.

Crossing-over occurs between homologous chromosomes.

Metaphase I

Homologous pairs become aligned in the center of the cell.

Anaphase I

Homologous chromosomes separate.

Telophase I

This stage is absent in some species

The second cycle in Meiosis includes the same stages for the first cycle except that they take place in cells with half the chromosomes.