A brief description

Introduction

Grrrrreetings. I am Purr-ofessor Mayo Seas.

You meow-st be curious about Meiosis.

Worry not, fur-iend. I shall guide you.

What is Meiosis?

Things will get verrry meow-xiting, and confusing, really fast.

To deeply understand meiosis, you must furst be familiar with mitosis. Luckily, my dear sister Mayto was kind enough to give a little lesson. Do check it out, fur-iend.

Meiosis is a cell division process in sexually reproducing organisms that reduces the chromosome number in gametes (egg and sperm). In humans, body cells are diploid, meaning they have two sets of 23 chromosomes from each parent. To keep this balance, egg and sperm must be haploid, each with one set of 23 chromosomes.

How does this happen? Meiosis ensures each gamete has 23 chromosomes, so when an egg and sperm unite, the fertilized egg has 46 chromosomes, and all cells in the resulting human will also have 46 chromosomes. Additionally, there is Meiosis 1 (PMAT1) and Meiosis 2 (PMAT2).

Important contrasts

As I have stated, prior knowledge about mitosis aids in knowing more about meiosis. They are very similar purr-ocesses. The most notable ones are:

- Mitosis and meiosis both have PMAT stages, with meiosis having 2 rounds of it and mitosis only having 1. This implies that mitosis only produces 2 cells and the latter producing 4.

- Mitosis occurs for growth and repair. Meiosis occur in reproductive cells (egg and sperm cell). This means that two diploid cells with identical genetic info is produced by mitosis, while meiosis produces four haploid cells with different genetic information.

You must be wondering my fur-iend, as to why meiosis produces different genetic info. This is because the information is taken from each parent, ensuring that each of their traits have a chance to carry over to their child. Mitosis cells with identical information because their function is for growth and repair.

- One of the most important ones to note: Prophase 1 of meiosis undergoes a process wherein chromosomes make contacts with each other (chiasmata), and 'crossing over' occurs. This is where chromosomes exchange sections of DNA. As mentioned, it generates genetic diversity while being crucial mechanically to hold homologous chromosomes together. In mitosis, this process does not exist.

- The first metaphase also differs. For mitosis, only a single chromsome (pair of chromatids) line up along the metaphase plate, getting cleaved into two sister chromatids. Sister chromatids are identical, so the orientation of the chromosome does not carry meaning. For meiosis, pairs of homologous chromosomes line up. They are oriented randomly with respect to the cell poles (law of independent assortment).

Purrrhew. I apologise for giving out so much information in one go, but you will realise soon, fur-iend, that this makes learning meiosis much easier fur you. I will be skipping PMAT1 of meiosis, as key differences of it with mitosis' purr-ocess has already been discussed.

Round 2 of the PMAT cycle in Meiosis

Prophase 2

[This is Pur-ofessor Mayo. I have turned myself into a diagram. This ability might be familiar to you, as my sister Mayto can do the same.]

When the first meiotic division (PMAT1) ends, two cells now exist, each with the same number of chromatids as the parent cell. PMAT2 starts with two cells.

In Prophase 2, the spindle fibers attach to contromeres in preparation for the second division.

Metaphase 2

The nuclear envelope reforms around the chromosomes and chromosomes line up individually at the cell's equator (known as the metaphase plate).

Anaphase 2

[This process seems familiar.. I hope you have realised. You're meow-come for making it clearer.]

The centromeres of the sister chromatids in each cell is cleaved, allowing the chromatids to segregate to opposite poles of the cell, at which point they are called chromosomes.

Telophase and Cytokinesis

Meow-ch like mitosis' telophase, a nuclear membrane reforms around the newly separated chromosomes. They begin to uncoil and become less condensed.

The cell plasma membrane pinches, leaving two daughter cells with separate plasma membranes. Four haploid cells (gametes) are produced, each with a single set of chromosomes.