Comparing Mitosis and Meiosis – Cell Division

00:00 So, now that we have established mitosis from meiosis, I'd like you to recall which division is the reduction division. Where does the cell become haploid? The key here to remember, I can't emphasize it enough, is haploid happens at meiosis I, right. So keep that in mind.

00:27 Let's compare mitosis to meiosis very quickly. We know that meiosis has two phases and mitosis has only one phase. We know that meiosis looks very much like mitosis in meiosis II because we're separating sister chromatids. Meiosis I doesn't look anything like mitosis because we're separating homologous chromosomes. I mean it looks something like it because we're separating, I mean we have all the same spindle fibers and all the apparatus is the same, but meiosis I is very different because of the homologous chromosome pairing. Now, also we end up with identical cells at the end of mitosis. And at the end of meiosis we end up with four genetically distinct gametes or sperm and eggs. So we can go all the way through meiosis I, and it's not until meiosis II that things start looking the same. Many questions you will run into here concern the chromosome number. How many of what are in prophase. How many of what are aligning on the metaphase plate. So, diagram these processes, compare and contrast, think about the number of chromosomes and how many molecules of DNA end up in meiosis I and how many molecules of DNA end up in each cell at the end of meiosis II.

01:57 And compare and contrast those to what's happening during mitosis. Who pairs on the metaphase plate is the critical question. If you understand that, you're really set up for success. So in this lecture, we recalled the language of chromosomes. And I hope you can see how important it is to really have a great understanding of those, of that language. And in addition to that, we started to distinguish features of meiosis. One of those was the genetic recombination. We have pairing of homologs and synapses. So we have crossing over, exchange of genetic information. We also have arrangement of chromosomes on the metaphase plate. It's random. So, we mix things up during meiosis.

02:44 We also should be able to summarize how genetic variation occurs during meiosis.

02:50 So those were the mechanisms to acquire that. And also relate meiosis to gamete formation.

02:57 So how does meiosis reflect in the female reproductive system versus the male reproductive system.

03:02 And finally, really good idea to be able to line these three events up and compare and distinguish between mitosis versus meiosis I and then meiosis II. So hopefully this lecture clarified for you some of the details of what's going on during meiosis and why meiosis is important for sexual reproduction.

03:28 Thanks so much. I look forward to seing you in a future lecture.