what is knob heterochromatin? 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.

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
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> chromosome breakage and chromatin loss
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> sex differences in recombination

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