Medical/Science History Question

[applyingsucks]

I am interested in the history of chromosomes. In particular who numbered the human chromosomes 1-22, x,y. Why are they numbered in this way? I originally thought it was in size order (bps), but it is not.

If anyone knows when, why, or how chromosomes were named please shed some light.

Thanks.

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[Droopy Snoopy]

I am interested in the history of chromosomes. In particular who numbered the human chromosomes 1-22, x,y. Why are they numbered in this way? I originally thought it was in size order (bps), but it is not.

If anyone knows when, why, or how chromosomes were named please shed some light.

Thanks.

Completely arbitrary, the numbering system was introduced in 1960 by some committee. You can google as well as I can, so I'll let you investigate deeper if you'd like.

 

[applyingsucks]

Does anyone know how chromosomes were numbered? I cant find this information anywhere. Someone one here has to know the answer.

 

[Uncle Izzy]

I'm almost positive that it is done by size. While we can currently count the number of base pairs in a chromosome, the original numbering was done based on microscopic appearance. Take a look at any karyogram out there (google image search karyotype to see that they are consistely smaller as chromosome # goes up with the exception of X and Y... see below).

The amount of condensed chromatin in a particular chromosome can vary and as such, a chromosome with more base pairs may in fact appear smaller microscopically when it is in fact bigger. Karyotyping existed prior to the ability to do sequencing or accurate sizing for DNA fragments that large and thus the numbering was based on microscopic size.

Pairing is done based on centromere location and banding pattern.