So now that we've introduced the first half of meiosis, which is meiosis 1 in our last lesson video, In this video, we're going to introduce the second half of meiosis, which is meiosis 2. And so recall from our last lesson video of meiosis 1 that meiosis 1 starts with a diploid cell, and it ends with 2 haploid daughter cells. But these haploid daughter cells still have replicated chromosomes, which means that cell division is not yet over with. And so these 2 haploid daughter cells that result from meiosis 1 are going to transition into the second half of meiosis, meiosis 2. And so in meiosis 2, each of the haploid daughter cells produced in meiosis 1 is going to divide, and that's going to end up forming a total of 4 genetically diverse haploid gametes. Now later in our course, we'll talk about how this genetic diversity arises during meiosis, but for now, we're gonna focus on the events of meiosis 2. And in terms of the events that occur in each phase of meiosis 2, it actually turns out that meiosis 2 is almost exactly the same as mitosis. And really the only difference is that mitosis starts with a diploid cell, whereas meiosis 2 starts with haploid cells from meiosis 1. But outside of that, meiosis 2 and mitosis are practically the same. And so very, very similarly to mitosis, chromosomes are going to align in just one single file row during metaphase 2. And that's exactly what happens during metaphase of my mitosis. The chromosomes align in 1 single file row. And recall from our last lesson video that this was not the case for meiosis 1, metaphase 1. Because during meiosis 1, metaphase 1, chromosomes did not align in 1 row, The chromosomes aligned in 2 rows, and that makes a big difference. And if we take a look at our image down below of meiosis 2 right here, what you'll notice is that it also has very very similar phases to mitosis in terms of having a prophase, metaphase, anaphase, and telophase, but what you'll notice is that each of these phases is followed up by the number 2. So we have prophase 2, metaphase 2, anaphase 2, and telophase 2 to indicate that these are the phases that belong to meiosis 2. And again, really meiosis 2 is almost exactly the same as my ptosis. And so what you'll notice is the events here are going to be exactly the same. And really, even though we're not showing you a prometaphase, between prophase and metaphase, the events of prometaphase are still occurring, they're just occurring, they're being batched here with prophase. And so that's something important to keep in mind. And really, meiosis 2 is mitosis just occurring immediately after meiosis 1. That's a way to think of it. And so notice that during metaphase 2 of meiosis 2, the chromosomes are aligning in just one single file row instead of aligning in 2 rows like what we saw during meiosis 1. And, also, very very similarly to mitosis, during meiosis 2, sister chromatids are actually going to separate and be divided during anaphase 2 of meiosis 2, just like sister chromatids are separated during anaphase of mitosis. And so if we take a look at our image down below at anaphase 2, notice that these replicated chromosomes are being divided, and so the sister chromatids are being separated and divided from each other. And so notice that, this sister chromatid here is going in this direction whereas this one here is going in the opposite direction and this sister chromatid here is being pulled into this direction and this one here is being pulled into this direction over here. And so, notice that, anaphase 2 here is occurring in each of the haploid daughter cells that results from meiosis 1. So prophase 2 occurs in each of these cells. Metaphase 2 occurs in each of these cells, and so on. And so, again, the phases of meiosis 2 are practically the same as the phases of mitosis. And really the only difference is that prophase, my meiosis 2 is starting with haploid cells instead of starting with diploid cells. And, of course, because each of these cells is going to undergo a cell division, there's going to be a total of 4 cells that are going to result, and these 4 cells are all haploid. And so you start with haploid cells in meiosis 2, and you end with haploid cells as well. And so, that's why it's called equational division at times since the ploidy number remains equal. And so this here really concludes our brief introduction to meiosis 2, the second half of meiosis and how really it's going to result to, in forming 4 genetically diverse haploid gametes. And so these 4 cells here, you could imagine, would either be sperm or egg, depending on if it's male or female. And so again, this here concludes our introduction to meiosis 2, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
2
Problem
Problem
Which statement describes a major difference between meiosis II and mitosis in a diploid animal?
a) Homologous chromosomes align on the metaphase plate in meiosis II.
b) Sister chromatids separate in mitosis, and homologous chromosomes separate in meiosis II.
c) Meiosis II occurs in a haploid cell, while mitosis occurs in diploid cells.
d) Meiosis II is known as 'reductional division' while mitosis is known as 'equatorial division'.
A
Homologous chromosomes align on the metaphase plate in meiosis II.
B
Sister chromatids separate in mitosis, and homologous chromosomes separate in meiosis II.
C
Meiosis II occurs in a haploid cell, while mitosis occurs in diploid cells.
D
Meiosis II is known as 'reductional division' while mitosis is known as 'equatorial division'.
3
Problem
Problem
During which of the following stages of meiosis do homologous chromosomes pair up and align along the metaphase plate of the cell?