Chromosomes vs Chromatids

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Offline LukyTom

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Chromosomes vs Chromatids
« on: 11/08/2009 13:23:00 »
It is my understanding that in the human cell, there is 23 pairs of chromosomes, or rather 46 single chromosomes. The pairing are homologus and only occurs during mitosis and meiosis. These two strands are joined by a centromere, and each strand is known as a chromatids.

So my question is, what is the difference between a single strand of Chromosome, and a chromatid. What is the formal defination of a chromatid. Is it one arm of a chromosome, seperated by the centromere.

Also, when not dividing, do the chromosomes, lie freely in the nucleus, detached from pairing?
« Last Edit: 11/08/2009 13:34:17 by LukyTom »


Offline Nizzle

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Chromosomes vs Chromatids
« Reply #1 on: 13/08/2009 14:04:07 »
1 Chromosome has two Chromatids, joined together by the centromere.
1 Chromosome pair has four Chromatids.

"a single strand of chromosome" does not exist. A chromosome is composed of two strands of chromatid.

When cells are not divided, the DNA floats around in the nucleus in condensed and free accessible genetic material, called heterochromatin and euchromatin respectively.

Heterochromatin is all the DNA which is not used in that particular cell type. Euchromatin is actively being transcribed to mRNA which then leaves the nucleolus.

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