Chromosomes in meiosis.. HELP!! Please?

Question

so why do chromosomes in meiosis get divided in half?? WHats the purpose of that?

Answer 1

Meiosis is the production of sex cells, through cell division. It makes it so that two sex cells can come together to form a whole.

1/2 + 1/2 = 1

Answer 2

Because after the chromosome divides in half, it's ready to get fertilized.

In humans:

Here. You have a male. Males contain one-stranded chromosome gametes (sperms) in their sex organs.

Here. You have a female. Females contain one-stranded chromosome gametes (eggs) in their sex organs.

The male and the female mate. When the male gamete and the female gamete join together, they make a fertilized zygote. Or in other words, they just made a baby. The zygote has one chromosome from the male and one from the female.

Keep in mind that the chromosome is not the two-stranded "X". It is only one strand of the X.




Sometimes the chromosomes do not get divided in half. This may occur in males or in females. But the cell that did not get divided (the chromosome in it which did not get divided, in other words) still lives. If a person fertilizes the opposite sex's sperm/egg (the one that didn't orignially divide) it results in deformations because you have EXTRA chromosomes. Some examples of this are Down Syndrome. It's called polyploidy.

Answer 3

Meiosis and Mitosis is diverse. The mom and pa occasion purely works for Mitosis yields 2 cells and 23 chromosomes each and each...(it fairly is the chop up of the intercourse cellular or ovum) . Meiosis has 4 cells with 23 chromosomes each and each for a whole of ninety six!

Answer 4

Well, there are 2 types of "divisions" during meiosis:

1) There is one division that occurs in all cell divisions. In this case, each chromosome divides in half, so that one half of each chromosome goes to one of the daughter cells.
Why does this happen? Because before this cell division started, each DNA macromolecule had duplicated. Afterwards, each of them concentrated to form one chromosome, and so these chromosomes have duplicate information, and they look different (for instance, if the chromosome normally has 2 "arms", now it will have 4).
When each chromosome divides in half, it goes back to normal.
As I mentioned before, this happens every time that a cell divides (mitosis or meiosis), and in this way the transmission of the entire genetic information to the new cells is ensured: perfect copies are made, then each copy is distributed to a daughter cell .

2) The other type of division is quite different, and it's exclusive: it only happens during meiosis. In this special division, it is not half of each chromosome that goes to each daughter cell, but HALF OF THE CHROMOSOMES. But not at random: the chromosomes are present in a cell as homologous pairs, and it's one of each pair that goes to each daughter cell. This means that the resulting cells have only half of the normal chromosomes. And that's OK, because these cells are gametes or reproductive cells. Each gamete needs to combine and fuse with another gamete of the opposite sex to achieve the full complement of chromosomes. When the 2 gametes combine,a zygote forms, and from it a new individual will develop. Thus, the members of a pair of homologous chromosomes come originally from the 2 gamete that fused.


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Update: Sorry Gibbie, but normal human body cells have 46 chromosomes, that is, 23 pairs of homologous chromosomes of which 1 is the sexual pair (XX or XY). That is the diploid number, or '2n'.
The amount of chromosomes DOES NOT increase during DNA replication (a process that occurs before mitosis and meiosis); what gets duplicated is each DNA macromolecule, so that before the cell divides, each chromosome has twice the normal amount of DNA, hence twice as many 'arms' as it had before replication.

The only ones of our cells that have half as many chromosomes are the gametes. They have only 23 chromosomes (haploid number or 'n'), including 22 somatic chromosomes, each of them corresponding tot one of the homologous pairs that got separated, and 1 sexual chromosome (either X or Y).

Answer 5

They get divided in half so as to prevent chromosome doubling after each generation. If there is no meiosis..and each gamete has 46 chromosomes instead of 23..imagine one generation after the next...46+46=92..92+92=184...etc

Can't imagine what all of us would look like then. scary isn't it?

Answer 6

The half thing is confusing you. Chromosomes are wound up DNA. Humans have 22 chromosomes, plus 2 sex chromosomes, X and Y. After mitosis (G1 phase), there are 2n chromosomes, each containing one copy of DNA. 2n is diploid; we get one chromosome from mom and another from dad. During S phase, DNA divides, so the chromosomes now get two copies of DNA, each chromosome is now a pair of two chromatids, attached by a centromere. There is now 4n DNA content, but still 2n chromosomes. During M phase, chromosomes align along the metaphase plate, and each half of each chromosome (one chromatid) goes into a daughter cell. Thus the daughter cells have 2n chromosomes, and 2n DNA.

Once you get that, meiosis is a snap. During meiosis, DNA duplicates as normal, creating 2n chromosomes and 4n DNA content. Then, during teh first meiotic phase, both chromosomes attach to each other, creating a single complex containing 4n DNA, this is for genetic recombination and is critical for genetic diversity. Then, each chromosome is separated into a daughter cell (unlike in normal mitosis, the chromatids don't separate, and the daughter cells contain two copies of genetically identical chromosomes, ie just mom, whereas in mitosis the daughter cells contain one copy of each different chromosome, from dad and mom). After that, immediately there is another M phase, and here the chromosome containing 2 chromatids will separate, just like in mitosis. Each of these goes into a specialized daughter cell, either an oocyte or a sperm depending on sex of the adult.

See this picture, it's pretty simple.

Answer 7

Better for mix and match. You get half of you father's chromosomes and half of your mother's. All picked randomly during meiosis. Therefore you are not exactly like either parent. More variety.

Answer 8

without it there would be no life.