About this video
The video works through an AP Biology free-response question comparing mitosis and meiosis. It identifies shared features, including DNA replication before division, chromosome condensation, alignment at the center of the cell and cytokinesis. It then contrasts them: meiosis has two divisions and produces four haploid daughter cells, while mitosis has one division and produces two diploid daughter cells, with crossing over and independent assortment occurring only in meiosis.
You'll be able to
- name at least two events that are common to mitosis and meiosis.
- explain why meiosis produces four haploid cells while mitosis produces two diploid cells.
- explain how crossing over and independent assortment contribute to genetic variation.
Key words
- Mitosis
- A single division that produces two genetically identical diploid daughter cells.
- Meiosis
- Two successive divisions after one round of DNA replication that produce four genetically distinct haploid cells.
- Haploid
- Having one set of chromosomes, as in gametes.
- Crossing over
- The exchange of segments between homologous chromosomes that occurs during meiosis.
- Homologous chromosomes
- A pair of chromosomes, one from each parent, that carry the same genes in the same order.
Transcript
- [Voiceover] Both mitosis and meiosis are forms of cell division that produce daughter cells containing genetic information from the parent cell. Part a. Describe two events that are common to both mitosis and meiosis that ensure the resulting daughter cells inherit the appropriate number of chromosomes.
All right. So, really we just wanna, well, what are two commonalities between the two? Well, I can think of a bunch of them. You could start off saying, well, DNA replicates before going into either of them. So DNA replicates before either, before either. You could say, well, the chromatin condenses into chromosomes in both of them.
Chromatin, chromatin condenses, condenses into, into chromosomes. You could talk about chromosomes form, getting aligned near the center of the cell, attaching to, to, to fibers. You could talk about, we could talk about cytokinesis. Splitting the cells. So, cytokinesis, kinesis involved, involved in creation of separate cells.
Creation of separate, separate cells. In general the, your meiosis one has a lot of analogs with mitosis in general. You could keep looking, keep digging deeper and listing more and more. They just want me to describe two events. I've already described three. Well, I'll leave it at that for now.
In general, before you take the AP test, mitosis and meiosis are good things to know in detail, because you might see questions like this on the free answer section, or they're likely to show up in the multiple choice section as well. But I think this is sufficient for part a.
We've described at least two events that are common to both mitosis and meiosis. If you have extra time, you might try to list more. And then part b. The genetic composition of daughter cells produced by mitosis differs from that of the daughter cells produced by meiosis.
Describe two features of the cell division process that lead to these differences. Well, maybe the most obvious one, the biggest difference between them, is mitosis, mitosis involves one division, involves one division. Meiosis involves two. Meiosis involves, involves, not inolves, involves, involves two.
This leads to two daughter cells from mitosis, and four daughter, daughter cells from meiosis. Meiosis. That's a pretty big difference between the two. Another big difference, and this is related to this. Because, because meiosis has an extra division, has extra division, but DNA replicates once, like in, once, like in mitosis, the daughter cells from meiosis have half the number of chromosomes.
They have a haploid number of chromosomes. The daughter cells in meiosis have a haploid number of chromosomes, number of chromosomes. Chromosomes. So, and we could say, mitosis daughters have diploid, daughters have diploid number. And these are probably the two strongest differences.
But you could talk about other things. You could talk about crossing over occurring in meiosis but not in mitosis. You could talk about the separation and independent sortment of homologous chromosomes that you have. Homologous, each member of a homologous pair that you have in meiosis that you don't have in mitosis.
So there's a bunch of things you could talk about. And you could go into arbitrary detail. It's nice that they only have to list two in each of these, in each of these parts of question four.
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