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Jimmy asked in 科學及數學生物學 · 1 decade ago

chromosomes

My bio textbook said 1 chromosome consist of 2 chromatids, and human have 46 chromosomes. So is it means that there are 92 chromatids in a human cell??

Also, during mitosis, daughter cell have same number of chromosomes of parent cell.So do parent cell's Chromosomes meed to double and then divided by 2???? Thank you!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

2 Answers

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  • 1 decade ago
    Favorite Answer

    1) During the time right before mitosis starts (prophase), chromatin is coiled up to form pairs of chromosome. Also, DNA duplicated at the same time. Therefore, there are 92 chromatids in a human cell during the prophase.

    (P.S. in usual time/interphase/the time not doing mitosis, there is only chromatin but not chromosome; therefore, there will not have 92 chromatids in human cell during this period.)

    2) The chromosome of the parent cells need not to be double!!! As in (1) said, the DNA duplicated. However, the chromosomes do not duplicate. When DNA duplicated, the number of chromatids is 2 in a chromosome. The two chromatids separates during the mitosis and become the chromosome with 1 chromatids in the daughter cell, then it uncoiled and form chromatins again.

    2009-11-20 20:57:55 補充:

    To gicyclo98:

    During the mitosis, only the DNA would be duplicated/double, but the chromosome would not be duplicated/double

    Source(s): myself, myself
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  • HKOOO
    Lv 4
    1 decade ago

    (1)

    圖片參考:http://www.clt.astate.edu/mhuss/chromosome.jpg

    For a unduplicated cell, a chromosome is like the left figure above which have one chromatid only. For duplicated chromosome in metaphase of mitosis, a chromosome has two identical chromatids like the right figure above.

    So, there are only 46 chromatids in a human cell, but 92 chromatids in a human cell where chromosome is duplicated.

    (2)Yes. During mitosis, chromosomes meed to double and then

    divided by 2 during anaphase. in The appearance of duplicated chromosome is just like the above picture. After the separation, two chromatids will be separated and become the unduplicated like(left figure above).

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