why does it show a full chromosome in the cell after the first split, and a single chromosome in the final daughter cells?
Meiosis 1 consists of the chromosomes replicating, lining up on the spindle and each homologous chromosomes going to seperate poles, to form 2 cells. These 2 cells each have 2 choromosomes.
Meiosis 2, is the same as mitosis. It involves the chromosomes lining up on the spindle and the chromatids separate, leading to 4 haploid cells.
Oh okay! I thought some uni's only allow a levels to be completed over 2 years?
That's right, but I did all my exams in January so it's technically over 2 years. The school made that mistake with the year above us, who got barred from several university courses because they did modular exams at the end of year 11.
That's right, but I did all my exams in January so it's technically over 2 years. The school made that mistake with the year above us, who got barred from several university courses because they did modular exams at the end of year 11.
I'm having a problem understanding meiosis, so I posted a question in the bio forum along the lines of:
If the starting cell has 46 chromosomes, the 2 daughter cells have 23, why do the daughter cells after meiosis 2 have 23 also?
You are all free to answer
This confused me for the longest time.
A somatic cell has 46 chromosomes (which is basically one chromatid). But just before meiosis the DNA replicates so you have two sister chromatids, during meisos 1 the homologous chromosomes are separated, so you have half the number. So the daughter cells have 23 chromosomes, but you have to remember that each chromosome has TWO chromatids. During meiosis 2, much like mitosis, the sister chromatids are pulled apart. So the final daughter cells contain 23 chromatids (but for an annoying reason, you are still expected to call them chromosomes - maybe because usually chromosomes are just the one chromatid?)
There isn't actually any DNA replication between the two divisions.
(Maybe you've already got this sorted, but it helped me to write it out )
A somatic cell has 46 chromosomes (which is basically one chromatid). But just before meiosis the DNA replicates so you have two sister chromatids, during meisos 1 the homologous chromosomes are separated, so you have half the number. So the daughter cells have 23 chromosomes, but you have to remember that each chromosome has TWO chromatids. During meiosis 2, much like mitosis, the sister chromatids are pulled apart. So the final daughter cells contain 23 chromatids (but for an annoying reason, you are still expected to call them chromosomes - maybe because usually chromosomes are just the one chromatid?)
There isn't actually any DNA replication between the two divisions.
(Maybe you've already got this sorted, but it helped me to write it out )
I'm fairly sure it is wrong to call them chromosomes though, because chromosomes are almost always labelled as having 2 chromatids :|. If the chromatids are pulled apart into 4 new cells during mitosis 2 they don't magically become chromosomes unless they are about to divide again surely (>.<)