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Sagot :
Answer:
There are 16 chromosomes in each daughter cell after mitosis.
Explanation:
When we say 2n = x (x being any number divisible by 2), we mean that we have x chromosomes in total for every somatic (body) cell in that organism of a certain species. Now, what does n mean, you might ask. The n number is the maternal or paternal set of chromosomes from either the mother or father. For instance, let's take a human somatic cell with a diploid number of 46. This is the total number of chromosomes in the cell. Now, as it turns out, like any other species, half of them come from the father, and half of them from the mother. For humans, the number is represented as 2n = 46. The total is 46, and if you use algebra to solve for n, you will find that the n number is 46/2, or 23 chromosomes. Aha, the origin of the company name, 23 and me. See, 23 of these chromosomes came from your mother's egg, and 23 came from your father's sperm. They combined together when you were fertilized, giving you a total of 46 chromosomes, and two sets of them (maternal set n = 23; paternal set n = 23).
Now, sometimes books like to use hypothetical organisms, or real organisms with smaller chromosome numbers than humans so it's easier to imagine and also draw. For the case of 2n = 16, this means that there are 16 total chromosomes in the somatic cell (mitosis implies somatic cell, as this is the process for how somatic cells divide), with 2 sets of maternal and paternal chromosomes. In this case, each set has 16/2, or 8 chromosomes each. Eight come from the mother and eight come from the father to make a total of 16 in each somatic cell.
Now, before I go, let's address some common misconceptions. Firstly, when we say 2n = 16, for example, this means that every single somatic cell in the organism has 16 chromosomes total. It does not mean that the entire organism has 16 chromosomes in total, but each cell that makes them up does. So yeah, with millions of trillions of cells, there are a gigantic amount of chromosomes, but we are only interested in the single cells primarily, as the cell is the basis of function and understanding of disease states for every level of organization above that (tissues, organs, etc.).
Also, let's talk about chromosome numbers and organization. It really depends on your class and level of understanding, because this stuff can get really confusing. If any of this confuses you, then pay attention to the part that I wrote before. Now, before a cell starts to divide, the DNA double helix is never just hanging around as a loose string - because it would get very tangled! It's always wrapped around proteins called histones. So really, when the cell is not dividing, the DNA looks something like, at it's most "disorganized" level, beads on a string (called *chromatin*). Each string is 1 DNA molecule by the way. Now, before the cell divides, it has to prepare to do so by duplicating its DNA. This is done in the "S phase" of the cell cycle. The DNA is copied, but it is done so as a long, thin, chromatin fiber. Technically, to enter interphase of the cell cycle, the DNA chromatin (after it duplicates in the S phase) must condense further into what we call an "active" chromosome. So, there *are* chromosomes in interphase, but they're uncondensed chromosomes, and not the X ones that we are used to. Now, as the cell enters metaphase, this is when we start to see the famous X "metaphase chromosomes" that we can see with a light microscope, unlike the interphase uncondensed "active" chromosomes that are not visible. Then, as we get to anaphase, the famous X chromosomes are split into two *chromatids* ( X to > and <). Since these chromatids split from the replicated chromosomes (X), they are *also* called chromosomes. So we have 2 unreplicated chromosomes that came from the 1 duplicated chromosome (X), and they go to each of the daughter cells equally (1 chromatid to each daughter cell). Remember, in humans, the total chromosome number is 46, so this means that there are 46 replicated X's, and they split into 92 single, unreplicated chromosomes (chromatids), and half of the 92 go to one cell, and half go to the other, giving both cells 46 unreplicated chromosomes (chromatids). Just some food for thought. After this split process in telophase, the chromosomes become less condensed, likely back to being "active chromosomes" like in interphase, and then eventually back to the beads on the string (or something a little more condensed).
I'm a little confused on the meaning of undifferentiated chromosomes, but I assume it means unreplicated. Good luck!
Note: picture comes from Campbell Biology In Focus 2nd Edition.
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