From a piece of blank paper, cut out three sets of four cigar-shaped structures (a total of 12 structures). These will represent chromatids. Be sure each member of a set of four chromatids has the same length and girth. In set one, label two chromatids 'A' and two chromatids 'a.' Cut each of these chromatids about halfway across near their midpoint and slide the two 'A' chromatids together at the cuts, to form a single set of attached sister chromatids. Do the same for the 'a' chromatids. In the second set of four chromatids, label two 'B' and two 'b.' Cut and slide these together as you did for the first set, joining the 'B' chromatids together and the 'b' chromatids together. Repeat this process for the third set of chromatids, labeling them as 'D' and 'd.' You now have models for three pairs of homologous chromosomes, for a total of six chromosomes. Align the chromosomes of each daughter cell as they might appear in metaphase II of meiosis.

Question

Accepted Answer

Hello, everyone. Welcome back. Let's look at our next question. In meta phase two of meiosis two, the chromosomes align at the equator of the cell in preparation for their separation into the daughter cells, the sister chromatid of each chromosome are attached to each other at the centromere aligned in a single row along the equatorial plate. How is the alignment of chromosomes in meta phase two of meiosis different from the alignment of chromosomes in meta phase. One of meiosis. One choice a alignment of chromosomes in meta phase two is between cys chromatis of a single chromosome, not homologous pairs. Choice B the arrangement of chromosomes in meta phase two contributes to genetic variation. Choice c alignment of chromosomes in meta phase two is between homologous pairs of chromosomes. Then choice d alignment of chromosomes in meta faces two allows for crossing over to take place. So let's just think about the differences here. We've got meta phase one and meta phase two. And we recall that meta phase one. In that first process, we have homologous pairs lined up along the mid plate of the cell. So John True little uh chromosomes in their X shape each with two chromatis. We've got our homologous pairs in meta phase two. We've already separated our homologous pairs and we now have single chromosomes along the mid plate where our sister chromatid will be separated. So we can look here at choice. A which says the alignment of chromosomes in me phase two is between sister chromatid. That is correct, not homologous pairs. So that is correct. Also, we have homologous pairs and meta phase one, Cytra chromatis and meta phase two. So we already have a correct answer in choice. A and since we don't have any sort of all of the above or both this and that we can go ahead and say that that is our answer. But since this is an explanation to be thorough, let's go through our other answer. Choices in choice B it says the arrangement of chromosomes in meta phase two contributes to genetic variation. Well, what is it that contributes to genetic variation? And that would be recombination as a result of crossing over? Well, we don't have crossing over or at least not to any great extent of cys chromatid. That's not really something that takes place in a significant way. And it certainly wouldn't give us genetic variation as the sister chromatid are identical to each other. So where we have that genetic variation occurs when our homologous pair because one is maternal and one is paternal, they have different sets of alls crossover physically and recombine and that would occur in meta phase one. That's where crossing over can occur since we need to have the two different chromosomes with different alleys recombining. So that's why choice B is not correct. Choice C says alignment of the chromosomes in meta phase two is between homologous pairs, but that's not correct. That would be between the, just a single chromosome and its sister chromatid being separated. So choice C is not correct. And then choice D says the alignment of chromosomes in meta faces two allows for crossing over to take place. Well, that's in metaphyseal pairs for crossing over, as we said. So choice D is not correct. So we've definitely confirmed that when we're talking about how the alignment of chromosomes in meta phase two is different from the alignment of chromosomes in meta phase one. Our correct answer is choice a, the alignment of chromosomes in meta phase two is between cy chromatis of a single chromosome, not homologous pairs. See you in the next video.

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Key Concepts

Chromatids

Homologous Chromosomes

Metaphase II of Meiosis