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Chromosome sizes?

ANITA L. HAWKINS ahawkins at welchlink.welch.jhu.edu
Wed Sep 11 13:03:48 EST 1996

On 5 Sep 1996, Jun-Zhi Wei wrote:

> Could anyone tell me the actual sizes (how many microns) of double minute
> chromosomes, the largest and the smallest chromosomes in metaphase human
> and mouse cells?  Thank you.
> J.-Z. Wei

This is not really an easy question... length (in microns) depends on the 
stage of contraction of the chromosomes. For instance, there is roughly a 
20:1 reduction in apparent length between prophase chromosomes and the 
same chromosomes after an overnight colchicine incubation (they'll look 
like little cubes instead of rods). This is not a change in the length of 
the DNA per se, just a change in packing.

Overall, mouse chromosomes are "shorter" than human, I'd guess (from 
memory here) the longest mouse chromosome to be about 1/3 the length of 
the longest human chromosome, at roughly the same level of condensation. 
But again, there is no "standard" to measure them against.

DMs (double minutes) can also vary quite a bit in size, from dust-like to 
chunky little mini-chromosomes. Even within a single cell line/tumor. 

Hope this is some help...

Anita Hawkins
Oncology Cytogenetics
The Johns Hopkins Hospital
Baltimore, Maryland, USA

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