 Have you ever asked yourself how you grew to become the person you are today? How did you grow from a baby to the person you see in the mirror? Does this process have anything to do with how plants grow? And what about bacteria? Well, today we are going to discuss a process known as cell division, which is involved in answering all of these questions. Cell division has many functions, which may be different in different organisms. Its primary functions are involved in the reproduction of single-celled organisms, in the growth and development of cells, and in the renewal of tissues. And this whole process involves duplicating genetic material to produce daughter cells. Now there are different types of cell division, such as binary fission, mitosis, and meiosis. And all of these processes replicate the cell's genetic material before starting the process of division. So, first we are going to explore binary fission, which is the main method of asexual reproduction in prokaryotes. The process involves splitting one mother cell into two diploid daughter cells with identical genetic material. So here's what the process of binary fission looks like. Note that this is involving a prokaryote with circular DNA. Replication starts at the origin of replication, which splits into two, duplicating itself. And we can see this origin of replication in red at the top of the diagram on the right. Next, the origins of replication migrate to opposite poles of the cell, and the rest of the DNA is duplicated as this happens. The cell then pinches to make a cleavage phyro, and eventually this pinch results in the split of the cell into two identical daughter cells. Moving on to mitosis, this is a process that helps eukaryotes grow through asexual reproduction. Similarly, to binary fission is a process that starts with a mother cell dividing into two identical and new daughter cells. Now, we can view mitosis by splitting the cell's life cycle into six phases, which are the prophase, the metaphase, the anaphase, the telephase, and cytokinesis, or IPMAT-C for short. So here is what the six phases look like, and note that the largest phase is the interphase, which is split into a G1, an S, and a G2 phase. Mitosis then occurs, which includes the prophase, metaphase, anaphase, and telephase, followed by cytokinesis, which marks the end of mitosis. This is where the cell prepares for cell division, and it consists of the G1 phase, where the cell grows and copies organelles, the S phase, where the cell synthesizes a new copy of DNA in the nucleus, and the G2 phase, in which the reorganization of cell contents and further growth occurs. During prophase, the genetic material within the cell's nucleus becomes condensed into chromosomes so that they do not become entangled with one another. There is also the beginning of the formation of mitotic spindles, which are involved in the next phase. And finally, the nuclear envelope starts to break down. During metaphase, chromosomes begin aligning along the cell middle, known as the metaphase plate. Centrosomes, which are organelles that hold the spindle fibers, lie at the end of the cell. And the spindles then reach out of these centrosomes and attach to the chromosomes that are aligned along the middle. In the anaphase, sister chromatids are pulled apart, and note that chromatids are one half of a duplicated chromosome, and sister chromatids are the identical copies of a chromosome that are joined together by a common centromere. So the split sister chromatids, now their own chromosomes, now move to the poles of the cell, and the cell then begins to elongate. And we can see this in this diagram here. In the telophase, two new nuclei start to form, one for each of the daughter cells that will remain after mitosis. Chromosomes then decondense, and the cleavage fire begins to form, similar to in binary fission. Cytokinesis is simply the moment where the pinching of the cell finally results in the two daughter cells. So it is the final cleavage of the material that results in the two cells. For some extra information, this complete division is facilitated by the construction of actin filaments in animals, but by the growth of a cell plate in plants. So this is what this overall process looks like with the interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. And note that this process starts off with one cell and ends with two diploid cells, which are identical to the original one. We'll now move on to meiosis, which is similar to mitosis in some ways, but some of the differences are outlined below. Firstly, the cell cycle we previously discussed does not just occur once like in mitosis, but it actually occurs twice, with the exception of the interphase, which only happens once in both. These two cycles are known as meiosis one and meiosis two. Secondly, meiosis results in four haploid cells, meaning they contain one set of chromosomes. And lastly, these haploid daughter cells are different to the diploid mother cell, unlike mitosis, where the mother and the daughter cells are identical. So this is an overview of what this process looks like, and let's try to pick out some differences when comparing to the process of mitosis. We can see that the prophase, metaphase, anaphase, telophase, and cytokinesis occur twice, eventually resulting in four daughter cells. Another key difference to realize is in metaphase one, or M1, where homologous pairs of chromosomes align on either side of the equatorial plate in the cell, unlike mitosis, where individual chromosomes line along the equator. Now here, we have meiosis one summarized, and we now know most of these processes from learning about mitosis. But just note that there are some differences, such as the fact that crossing over occurs, the process by which chromosomal segments can be switched between two homologous chromosomes, resulting in the recombination and exchange of genetic material. And again, to repeat, in metaphase one, homologous pairs align on either side of the equator, rather than individually on the equator, like in mitosis. And here is the process of meiosis two. The main thing to note here is that the result of this process is four haploid daughter cells, as previously discussed. This table presented here nicely summarizes everything we learned today, and is a good representation of the differences between these three types of cell division.