Meiosis

The following video shows the stages of meiosis. Remember that meiosis is the process of producing haploid gametes.

The only thing missing from this video is crossing over where genetic material is swapped between homologous chromosomes.

This second video includes crossing over and shows the same process in a little different way. Remember that Meiosis and Mitosis are similar processes, but the end result is different because Meiosis has a second division and produces haploid gametes instead of diploid body cells.

Mitosis Meiosis
Goal Identical Cells Sex Cells
(egg & sperm)
Divisions Divides Once Divides Twice
Outcomes 2 Identical Cells 4 Sex Cells
Chromosomes All 46 chromosomes are present
(2N)
Only 23 chromosomes are present
(N)

Meiosis and Non-disjunction

The following clip looks at the stages of meiosis and does a good job explaining it.

The next clip identifies the differences between male and female gamete formation.

The following clip looks at the process of non-disjunction in meiosis II which can lead to the development of monosomies or trisomies.

The second clip looks at the process of a non-disjunction in meiosis I which can lead to the development of monosomies or trisomies.

Notice the number of chromosomes in each gamete. Notice the difference in what is occuring with the spindle. How does non-disjunction in meiosis I differ from non-disjunction in meiosis II?