Question

What are the differences between meiosis I and meiosis II?

Answer 1

1. In meiosis I, homologous chromosomes separate, while in meiosis II, sister chromatids separate.
2. Meiosis II produces 4 haploid daughter cells, whereas Meiosis I produces 2 diploid daughter cells.
3. Genetic recombination (crossing over) only occurs in meiosis I

Explanation:

Meiosis is a way sex cells (gametes) divide. Since sex cells determine the genetic code of offspring, meiosis attempts to create unique combinations of chromosomes in gametes.

Meiosis I is the first stage of this cell division, where pairs of chromosomes are split up. We can see how the process occurs in the following diagram:

Looking at the diagram, you might notice there are a lot of differences between meiosis I and meiosis II, including:

1. In meiosis I, homologous chromosomes separate, while in meiosis II, sister chromatids separate.
2. Meiosis II produces 4 haploid daughter cells, whereas meiosis I produces 2 diploid daughter cells.
3. Genetic recombination (crossing over) only occurs in meiosis I.

If you didn't understand any of those difference or didn't notice them, it's okay, because I'm going to explain it below in detail:

Diploid Cells have two sets of chromosomes, while Haploid Cells have only one set of chromosomes. Here's how the chromatids and chromosomes split in meiosis, in terms of n.

The cell has 2 pairs of chromosomes after DNA replication, and 1 pair of chromatids is distributed to each cell during meiosis I. In meiosis II the daughter cells now have 1 chromatid each.

In meiosis II , there are 4 daughter cells produced, whereas in meiosis I , there are 2 daughter cells produced. However, notice in the above image the chromosomes in each daughter cell. For meiosis II, the daughter cells have only one set of chromosomes.

However, the cells in meiosis I have two sets of chromosomes. The first stage of meiosis II splits the pair of homologous chromosomes apart, so that 2 pairs of chromosomes are left, while the second stage splits each pair of sister chromatids to have half the number of chromosomes a normal cell would have, and is therefore haploid.

Also, genetic recombination only occurs in meiosis I. Genetic recombination occurs when two chromosomes exchange certain sections of their DNA to produce genetically unique genetic combinations.

However, since the gene combinations produced in meiosis I are already genetically unique, the chromosomes in meiosis II do not undergo genetic recombination a second time.

There are other differences, like differences in the equatorial plane and convergent arms, but these three are the most important ones.

Answer 2

meiosis I is for homologous recombination and separate chromosome in 2 cells resulting in only 1 chromosome of each type
meiosis II forms haploid gametes by separating sister chromatids

Explanation:

Look at the following figure to understand what is the difference

Following are the differences in Meiosis I and Meiosis II in brief:

1. After DNA replication each chromosome have four sister chromatids(4n). Once entering in meiosis I, chromosome of same type (homologous chromosome) will pair, for example, chr1 of father will match with chr1 of mother (shown in red and blue)
2. After meiosis I, the two cells formed will have only 1 chromosome of a type, that is either fathers' or mothers' (2 cells with 2n). A point to note is that here the sister chromatids are not separated just the homologous chromosomes separate.
3. once the cells enter Meiosis II sister chromatids are divided, and thus, in the end, you get haploid cells (4 cells with n).