Cell Division: Meiosis (Nursing)

00:01 So speaking of babies, when it comes to reproductive cell division, we're going to do things a little differently.

00:08 And the reason why is because we actually want a different result than that of mitosis.

00:14 So in reproductive cell division, our reproductive cells or the sperm cells in male or the oocytes cells in females are going to undergo a division so they end up with half the number of chromosomes than what they started with.

00:30 So what do I mean by that? Remember in all of your cells, you have two sets of 23 chromosomes for a total of 46 chromosomes.

00:41 So let's think about it in terms of shoes.

00:44 So you have a right shoe and a left shoe, but they are a pair of shoes.

00:50 That's how your chromosomes are.

00:52 You have one chromosome from your mom and one chromosome from your dad and together, they make a set of chromosomes.

01:00 So remember in S phase, we duplicated all of our chromosomes so now, they are held together in an x-like form and we we refer to them as sister chromatids.

01:12 In the first part of meiosis or meiosis I, what I'm going to do is separate the two homologous chromosomes (the shoes) into daughter cells after they have been modified by recombining parts of each other by crossover exchanges in Prophase I.

01:29 They're still duplicated or in the 'sister chromatid form' but they are now in separate cells.

01:37 This is referred to as going from diploid to haploid.

01:45 Now in meiosis II, my haploid cells still contain the sister chromatids or the Xs where the two duplicated chromosomes are now in the same cell, and I need to separate those two duplicated chromosome into individual chromosomes in each cell.

02:03 So at the end of meiosis II, you started with two cells and you end up with four separate cells each with half the number of chromosomes that you started with.

02:16 And now for reproduction to occur, we allow one cell to fuse with another and now we have two sets again.