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I am reading a paper which discusses Maize Genome Structure. Descriptions of the structure is given in the papers introduction. I know about heterochromatin "heterochromatin stains intensely, indicating tighter packing. Heterochromatin is usually localized to the periphery of the nucleus" but, could someone explain what is knob heterochromatin?

thanks for help.

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up vote 1 down vote accepted

Here's a good summary of knobs, which says that they are "typically telomeric," "tandemly repeated DNA sequences [that] appear as distinct, heteropycnotic regions located at certain sites on specific chromosomes and look much like beads on a string" and are involved in:

increased recombination

neocentromere activity

preferential segregation

chromosome breakage and chromatin loss

sex differences in recombination

The introduction to this paper gives some of the same information.

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I found it in this article :

Heterochromatic knob A chromosomal region that can be identified microscopically as being darkly stained compared with surrounding chromatin. DNA sequence analysis has shown that knobs often contain highly repeated DNA sequences. They were described initially in the 1930’s by McClintock during her studies of maize chromosome structure

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If you copy a paragraph verbatim from another source, please indicate this clearly by naming and linking the source and using a blockquote. Else one might get confused about which parts of the answer you wrote yourself, and which are taken from other sources. – Mad Scientist Oct 4 '13 at 7:56
thanks for the advice I did not know that – Medhat Helmy Oct 4 '13 at 9:35

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