Number of chromosomes in mitosis and meiosis ? Watch

nisha.sri
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Hey,
How do you know how much chromosomes there are in each stage ?
So if there was 75 chromosomes how many would there be in each phase ?

Thank you x
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AortaStudyMore
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(Original post by nisha.sri)
Hey,
How do you know how much chromosomes there are in each stage ?
So if there was 75 chromosomes how many would there be in each phase ?

Thank you x
Well first of all you can't have an odd number of chromosomes (unless you have an aneuploidy), so I'll change the number to 74 to answer your question. In mitosis, the number of chromosomes is kept constant, so that each daughter cell has the same number of chromosomes. During interphase, the amount of DNA is doubled, so that you have 148 chromatids. The chromosomes all line up in the middle of the cell during metaphase and then the chromatids separate during anaphase. In meisosis, the process is a tiny bit more complicated. You have meiosis I and meiosis II. Meiosis I is when the whole chromosomes are separated into 2 daughter cells, so each daughter cell will have half the original amount (they become haploid), ie 37 in this example, and then meiosis II is basically the same as mitosis, where the chromatids are separated. So you end up with 4 daughter cells with 37 chromosomes each.
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nisha.sri
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(Original post by AortaStudyMore)
Well first of all you can't have an odd number of chromosomes (unless you have an aneuploidy), so I'll change the number to 74 to answer your question. In mitosis, the number of chromosomes is kept constant, so that each daughter cell has the same number of chromosomes. During interphase, the amount of DNA is doubled, so that you have 148 chromatids. The chromosomes all line up in the middle of the cell during metaphase and then the chromatids separate during anaphase. In meisosis, the process is a tiny bit more complicated. You have meiosis I and meiosis II. Meiosis I is when the whole chromosomes are separated into 2 daughter cells, so each daughter cell will have half the original amount (they become haploid), ie 37 in this example, and then meiosis II is basically the same as mitosis, where the chromatids are separated. So you end up with 4 daughter cells with 37 chromosomes each.
Oh yes I meant 74
But I thought that in prophase of mitosis there's 148 and this is the same for all the phases in mitosis except from after telophase ?!
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AortaStudyMore
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(Original post by nisha.sri)
Oh yes I meant 74
But I thought that in prophase of mitosis there's 148 and this is the same for all the phases in mitosis except from after telophase ?!
erm kind of, basically, each chromosome is copied, and each copy is attached to the other at the centromere, therefore producing the classical X shape that you often associate with a chromosome. These copies are genetically identical to the original and are called chromatids. Generally, you still consider the chromatid pair as one chromosome, it's not like you have 148 genetically different chromosomes. It'd be more accurate to say that there are 74 pairs of chromatids I reckon
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