Meiosis is the cell division process for the production of gametes. Gametes are sex cells: sperm in males and eggs in females. 

Meiosis results in the production of four daughter cells with exactly half as many chromosomes as the parent cell. The daughter cells are haploid, as they have half as many chromosomes. 
The parent cell is diploid since it has double the number of chromosomes as the daughter cells. 

When an egg cell and a sperm cell, which are both haploid, combine during fertilisation, they make a zygote which is diploid. 
Haploid + Haploid = Diploid

Unlike mitosis, meiosis is a two-step division process:
Meiosis I and Meiosis II. 

Homologous chromosomes form homologous chromosome pairs with each coming from each parent. They are similar in length, gene position and centromere location. 

In the first step of the division process (Meiosis I), the homologous pairs are separated. 
In the second step (Meiosis II), the sister chromatids are separated. 

Stages of Meiosis I:

  • Prophase I
  • Metaphase I
  • Anaphase I
  • Telophase I

Stages of Meiosis II:

  • Prophase II
  • Metaphase II
  • Anaphase II
  • Telophase II

Meiosis I

Interphase
Interphase is the phase of the cell cycle in which the cell copies its DNA in preparation for the cell division. 

The cell organelles double in number, the DNA replicates and protein synthesis occurs. 
The chromosomes are not visible and the DNA appears as uncoiled chromatin.

Prophase I
During prophase I, chromosomes begin to condense. 
Homologous pairs also form. The two match up at corresponding positions according to their length. 

Crossing-over occurs in this stage of meiosis. This means that fragments of DNA from each chromosome are exchanged between each other in the homologous pair. Crossing-over leads to variation in individuals of the same species. 

Crossing over
Crossing-over of DNA fragments

After crossing over, the spindle begins to capture chromosomes. 
Unlike mitosis, each chromosome from the homologous pair attaches to the microtubule from the opposite pole. 

prophase 1
Prophase I

Metaphase I
Homologous pairs line up at the equator. 

The pairs’ assortment at the equator is random. Their lineup at the equator is completely not fixed. This, like crossing-over, leads to variation in individuals of the same species. This is known as random assortment.

metaphase I
Metaphase I

Anaphase I
The homologues are pulled towards opposite poles. The sister chromatids however, remain attached to each other. 

Telophase I
The chromosomes arrive at the opposite poles. 
The chromosomes decondense and the nuclear membrane reforms. 

telophase I
Telophase I

Cytokinesis
The cytoplasm of the parent cell divides, forming two haploid daughter cells.


Meiosis II

No copying of DNA occurs in meiosis II. The cells that enter meiosis II are the ones that completed meiosis I. They are haploid but their chromosomes still consist of two sister chromatids. 

The main purpose of meiosis II is to separate these two sister chromatids. 

Prophase II
During prophase II, chromosomes begin to condense. 
The spindle forms and the microtubules begin to attach to chromosomes. 

The two sister chromatids of each chromosome attach to opposite spindles. 

Metaphase II
The chromosomes line up individually along the equator. 

Anaphase II
The sister chromatids separate and are pulled towards the opposite poles. 

Telophase II
The chromosomes decondense and the nuclear membrane reforms. 

Cytokinesis
In meiosis I, two haploid daughter cells are formed. 
In meiosis II, the two haploid daughter cells, each, form two haploid daughter cells. 
Therefore, in total, (2 x 2) 4 haploid daughter cells are produced.