I need to know mitosis and meiosis.?

Question

I am studying midterms, few questions are bugging me! ahk!

sucha as
1.what type of cells undergo mitosis and meiosis? and how many cells undergo?
2.when do chromosomes condense?
3.when does the nuclear membrane disappear and reappear?
4.what's the result of mitosis and meiosis regarding the number of chromosomes?
5.what happens before intherphase? like sub-stage interphase.

I am keep studying with my txtbook. If i get some answers, i will post some. Thank you

I am adding one more. Why checkpoints are imporantant in cell division?
also how many cells result from one cell that undergoes meiosis? Thank you for answering .

Answer 1

1- Meiosis happens in stem cells that give rise to gametes (sex cells).
Mitosis happens in all other cells.
In women every month only one stem cell goes through meiosis forming 4 haploid cells. In men many cells go through meiosis everyday.
Every other cell in body goes through mitosis in a daily basis to replace old and dead cell.
2- Before cell replication starts.
3- At the end of the prophase (in case of meiosis, end of the prophase 1)
4- Mitosis: diploid cells; Meiosis: haploid cells
5- Every thing but cell division: the cell obtain nutrients and when it gets close to cell division, it will duplicate its DNA and other organelles.

Answer 2

1.Mitosis: 1 cell splitting into 2 cells. This is asexual reproduction. Most cells in our body use mitosis to reproduce.
Meiosis: are gametes (contaning 2 chromosome, each comes from each parent) and is sexual reproduction ( because from 2 parent individuals). Meiosis occur to sexual reproduction so cells like egg cells and sperm cells are the cells types undergo meiosis.

2. Chromosome condenses to heterochromotins during prophase (the 2nd of total 6 phases in cell division) so the division can take place, either in mitosis or meiosis.
Cyclin(produce during Interphase {1st phase} of mitosis or meiosis) and cyclin-dependent kinase (cdk- floating in cytoplasm) form Mitosis promoter factor (MPF). MPF triggers mitosis to occur, meaning with no MPF, no mitosis or no cell division. So when division take place, the chromosomes condense.

3. Nuclear envelope dissolves ( not disappear) during prometaphase after the asters reach the poles of the cell.
Nuclear envelope reforms during telaphase at each end of the cells ( this moment 1 haploid or 1 diploid divided already into 2 or 4 cells ).

4. My guess is each cells should have many many chromosomes, and the chromosome will just double (called DNA replication) so the current number of chromosomes will be just double and then divided into its daughter cells (cells after divisions)
5. My guess is cell still just functioning normally because it has not yet been triggered by MPF (explained above) to start to divide.

Answer 3

Mitosis is body cells dividing normally into exact copies, meiosis is like reproductive cells (eggs in a woman, sperm in a man) dividing to have half the DNA of a normal cell. Mitosis has 23 chromosome pairs (or 46 chromosomes), Meiosis has 23 chromosomes and no pairs. That's where I forget most of bio, hope that helps...
A good way to remember is miTOsis (said mi"TOE"sis), oh that's in my toe
and
meiOsis (said mei"OH"sis) oh that's in the Ovaries