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no. of chromatids,dyads and tetrads

Genetics as it applies to evolution, molecular biology, and medical aspects.

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no. of chromatids,dyads and tetrads

Postby yee » Tue Jan 03, 2006 4:30 am

anyone pls help me to know how many chromatids are there in a simple

chromosome(one or two)

i think i'm missing the main concept in genetics

i m lost in tetrads and dyads too
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Postby Enzyme » Tue Jan 03, 2006 10:05 am

Mmmm... I think I don't know exactly the question you want to ask. Sure that I misunderstood, tell me.

In a simple chromosome there are two chromatids (also there are chromosomes with one chromatid. For example, before starting the mitosis, in G1 chromosomes have one chromatid).

But there are species which can have more chromatids, as Drosophila melanogaster, Chironomus tentans, etc which has politenic chromosomes (they round a thousand of chromatids).

About dyads and tetrads, dyads are the result of the first meiotic division in cells which has cell wall and tetrads are the result of the second meiotic division in those cells too. For example: in germinal cells of plants.

Did I answered your question?
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Postby aaroncjj_2020 » Mon Jan 16, 2006 2:21 am

in an easier way, in normal chromosome, there are one chromatid. when it undergo mitosis, during interphase, it'll duplicate the genetic material, and now the chromosome has two chromatids. during anaphase the two chromatids(sister chromatid) will separate and produce two chromosomes, each with one chromatid. hope this can help u.
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thanks

Postby yee » Tue Jan 17, 2006 3:18 pm

thanks for the explanation

however, i want to make sure whether my understanding really true

so,please let me ask u one question

that is ...does a simple chromosome have one chromatid and one centromere only?

P.s i tried to attach a file using paint but it is not an allowed extension

Looking forward to ur reply... :)
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Postby MrMistery » Tue Jan 17, 2006 7:27 pm

If you want to attach pictures be sure to save them in a *.JPG format, as we do not allow *.bmp, because of file size.
About centromere, that is only prezent during cell division, when homologos chromosomes attach
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
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Postby aaroncjj_2020 » Wed Jan 18, 2006 2:13 am

err....i hv a different point of view. every chromosome hv a centromere and a chromotid.
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thanks mr mistery

Postby yee » Thu Jan 19, 2006 4:02 pm

here is the attach file

pls choose the right one by telling 1st ,2nd or 3rd pic
Attachments
chromatids.JPG
it is the file i want to attach
(thanx mr mistery)
(22.15 KiB) Downloaded 136 times
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Postby aaroncjj_2020 » Fri Jan 20, 2006 8:54 am

left top pic
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Postby Enzyme » Sat Jan 21, 2006 3:17 pm

In your diagram: The correct pic is the one which is in the left top (the first one). The second pic misunderstands chromatid with chromosomic arm. And the third is wrong too.

Here I'm sending you another diagram. I hope it will be useful for you...
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chromatids.JPG
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