What happens to DNA during mitosis?

Question

I missed the day my teacher went over the pre-write for a BCR so I got a little confused, especially since we don't have textbooks at home yet. Our notebooks are being collected tomorrow and the BCR being graded as well.

Anyways, I pretty much understand the process of mitosis, but I just got confused with this question. More to the question is what are the steps (I guess of what the DNA goes through) and what the chromosomes do in these steps.

Another question I got confused by, even though it's probably obvious, is why the chromosome number is important in mitosis.

Sorry for being so desperate, but I really just want to go to bed. Even if you don't give me the answer directly (which you really don't have to), a website to help me (besides Wikipedia) would be much appreciated. Thanks for your help in advance =)

Answer 1

Here are the basics of what happens to the DNA and chromosomes.

Just before mitosis begins (during interphase) the DNA is replicated or copied.

During mitosis:
1. Prophase: the DNA starts in the form of chromatin which is long and stringy. The DNA wraps up and coils into shorter, more compact forms. That makes the double-stranded chromosomes. In humans the 23 pairs (46) double-stranded chromosomes appear. Also during prophase the nucleoli and nuclear envelope disintegrate and the spindle forms.
2. Metaphase: the spindle fibers attach to the centromeres (the center button-looking thing that holds the two sister chromatids of the chromosomes together). The spindle fibers push and pull on the centromeres to move them to the equator of the spindle. The legs/arms of the chromosomes can stick out any which way.
3. Anaphase: the spindle fibers pull on the centromeres until the centromeres split apart. The spindle fibers pull the sister chromatids to opposite poles of the spindle.
4. Telophase: the chromosomes begin to unwind and turn back into chromatin. This makes them look kind of puffy at first, and then they start looking like a grainy blob. This forms two equal sets of chromatin. Also during telophase the spindle disintegrates and the nucleoli and nuclear envelope reappear. This is the end of mitosis, but the daughter cells still have to divide.
5. Cytokinesis ends the cell cycle. In animal cells the plasma membrane pinches in at the middle of the cell in a place called the cleavage furrow. It dents in further and further, just like if you pulled a belt tighter and tighter, until the two daughter cells are pinched apart. In plant cells a cell plate forms across the center of the cell and new plasma membranes and cell walls are laid down along the cell plate. Either way, there are two daughter cells that are identical to each other. The two daughter cells have exactly as many chromosome as the original parent cell had because the DNA was copied right before mitosis, and the DNA was divided up evenly during mitosis.

Good luck. It's a complicated subject to miss.

I always teach my students that they can follow what the DNA does if they remember "double, shorten, line up, split, lengthen, daughters divide". There's a little tune that goes along with it, but I can't hum it for you online! Match those words with the parts of the cell cycle, "interphase, prophase, metaphase, anaphase, telophase, cytokinesis".

Interphase - DNA doubles
Prophase - DNA shortens to make chromosomes
Metaphase - Chromosomes line up on equator of spindle
Anaphase - Chromosomes split and sister chromatids are pulled to opposite poles
Telophase - Chromosomes unwind and lengthen to make chromatin again
Cytokinesis - daughter cells divide

Sorry - I get a little carried away with bio.

Answer 2

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RE:
What happens to DNA during mitosis?
I missed the day my teacher went over the pre-write for a BCR so I got a little confused, especially since we don't have textbooks at home yet. Our notebooks are being collected tomorrow and the BCR being graded as well.

Anyways, I pretty much understand the process of mitosis, but I just...

Answer 3

in interphase the dna replicates the helix "unzips" and duplicate. in prophase the chromatin (dna) condenses into chromosomes each chromosome is a pair of chromatids linked by a centromere. in meta phase the chromosomes line up in center of the cell. in anaphase the chromatids separate and they move toward opposite ends of the cell. in telophase the chromatids start to unwind into chromotin and the nuclear membran reforms.

also the number of chromosomes in the two resulting cells are the same as the original parent cell(this is not true in meiosis, or sex cell division, resulting cells in that case have only half as many chromosomes)

alos mitosis is defined as the division of the nucleus, when the cell actually splits it is called cytokinesis

Answer 4

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Most of the other organelles are distributed throughout the cytoplasm, so when the cytoplasm divides, some of the mitochondria, some of the golgi apparatus, some of the endoplasmic reticulum, some of the lysosomes, etc. end up in each of the two new cells.