Cell Division Question?

Question

How many chromatids are present in metaphase II in a cell undergoing meiosis from an organism in which the diploid number is 24?
a, 12
b, 24
c. 36
d. 48
e. 96



(answer is B but i don't get y) (i kinda can figure it out but then when i do it means that the diploid number is specifically talking about the # of chromosomes b4 duplication)

Answer 1

Here's the reason why it's 24.

Be sure you understand what the difference is between meiosis I and meiosis II.

If the cell starts with 24 chromosomes, then in prophase before meiosis I, all 24 chromosomes have their DNA copied, so the chromosomes each have two sister chromatids and will look like butterflies or clothespins - the usual way we picture chromosomes. So the 24 chromosomes have 48 chromatids.

The point of meiosis I is to get the homologous chromosomes away from each other and into separate cells. So the homologous pairs synapse, line up on the spindle's equator, and pull apart from their homologous twins during anaphase I. What do they look like? They're still double-stranded with two sister chromatids apiece. How many go into each cell at the end of meiosis I? Only 12 of the chromosomes go into each cell because they said goodbye to their homologous twins in this meiosis I. So these 12 chromosomes have two chromatids apiece for a total of 24 chromatids in each cell.

The whole point of meiosis II is to pull the sister chromatids apart at the centromeres so each new cell will get one sister chromatid from each chromosome - this just takes the double-stranded chromosomes and pulls apart the strands for the new cells. What did meiosis II start with? Cells with 12 double-stranded chromosomes (24 chromatids). During metaphase II they have lined up on the equator of the spindle, but they haven't pulled apart yet. So how many chromatids are there? 24.

As a note ... even though there are 24 chromatids, this cell is already haploid because there's only one of each kind of chromosome, even if these 12 chromosomes are double-stranded.

AFTER meiosis II is finished, each new cell will have 12 chromatids, or 12 chromosomes.

Answer 2

umm okay lets see if i remember my AP bio stuff...meiosis produces haploid cells right? so at the end of meiosis II we'll end up with 12 chromatids per cell, half of the diploid number. in metaphase II, when the chromosomes line up in the middle of the cell, this cell should have 24 chromatids still so that when the final split occurs, both daughter cells will only have 12 chromatids. these are the haploid cells. thats why there has to be 24 chromatids at metaphase II, before the cell splits.

Answer 3

12,

Answer 4

im not good at this kinda stuff, but are there 12 chromosomes because there are 2 chromotids in each?

Answer 5

12@ its half

Answer 6

a, 24
b48
c72
d96
e192