Mitosis and meiosis which comes first

The mitotic cell cycle is initiated by the presence of certain growth factors or other signals that indicate that the production of new cells is needed.

Somatic cells of the body replicate by mitosis. Examples of somatic cells include fat cells , blood cells , skin cells, or any body cell that is not a sex cell. Mitosis is necessary to replace dead cells, damaged cells, or cells that have short life spans. Meiosis is the process by which gametes sex cells are generated in organisms that reproduce sexually. Gametes are produced in male and female gonads and contain one-half the number of chromosomes as the original cell.

New gene combinations are introduced in a population through the genetic recombination that occurs during meiosis. Thus, unlike the two genetically identical cells produced in mitosis, the meiotic cell cycle produces four cells that are genetically different. Cell Division. Daughter Cell Number. Genetic Composition. Length of Prophase. Tetrad Formation. Chromosome Alignment in Metaphase.

Chromosome Separation. While the processes of mitosis and meiosis contain a number of differences, they are also similar in many ways. Both processes have a growth period called interphase , in which a cell replicates its genetic material and organelles in preparation for division. Both mitosis and meiosis involve phases: Prophase , Metaphase , Anaphase and Telophase. Although in meiosis, a cell goes through these cell cycle phases twice.

Both processes also involve the lining up of individual duplicated chromosomes, known as sister chromatids, along the metaphase plate. This happens in metaphase of mitosis and metaphase II of meiosis. In addition, both mitosis and meiosis involve the separation of sister chromatids and the formation of daughter chromosomes. This event occurs in anaphase of mitosis and anaphase II of meiosis.

Organisms that reproduce sexually have two copies of each chromosome, one from their father and one from their mother. A special form of cell division needed to produce sex cells - for example, sperm and eggs with only one copy of each chromosome. Fusion of the sex cells creates a new individual with two copies of each chromosome.

After each of these things go through mitosis, they can then go through the entire cell cycle again. Let me write this a little bit neater. Mitosis, that s was a little bit hard to read. Now what happens in meiosis? What happens in meiosis? I'll do that over here. In meiosis, something slightly different happens and it happens in two phases. You will start with a cell that has a diploid number of chromosomes. So you will start with a cell that has a diploid number of chromosomes.

And in it's interphase, it also replicates its DNA. And then it goes through something called Meiosis One. And in Meiosis One, what you end up with is two cells that now have haploid number of chromosomes. So you end up with two cells, You now have two cells that each have a haploid number of chromosomes. So you have n and you have n. So if we're talking about human beings, you have 46 chromosomes here, and now you have 23 chromosomes in this nucleus.

And now you have 23 in this nucleus. But you're still not done. Then each of these will go through a phase, which I'll talk about in a second, which is very similar to mitosis, which will duplicate this entire cell into two. So actually, let me do it like this. So now, this one, you're going to have four cells that each have the haploid number that each have the haploid number of chromosomes.

And they don't all necessarily have the same genetic informatioin anymore. Because as we go through this first phase, right over here of meiosis, and this first phase here you go from diploid to haploid, right over here, this is called Meiosis One.

Meiosis One, you're essentially splitting the homologous pairs and so this one might get some of the ones that you originally got from your father, and some that you originally got from your mother, some that you originally got from your father, some that you originally got from your mother, they split randomly, but each homogolous pair gets split up.