Chromosones

[djprescott]

How many chromosones are there in a human cell

[gravity]

yup thats right 23 pairs of chromosomes so 46 in all

[Peter Pedant]

Yeah 46

of course there are twiddly bits.....

This was established relatively late (1959). The normal number needed to be known before one could reliably ascribe Downs syndrome to one extra chromosome.

Germ cells - sperm and egg have 23 (haploid)

Cancer cells may have an abnormal number

Some cells in the placenta may not have the right number (syncytiotrophoblast)

I cant rmember if megakaryocytes (bone marrow = platelet precursors) have more than one nucleus, if yes then they willhave more than 46 chromosomes

Any cell just about to undergo division will have 2 x 46, except germ cells undergoing meiosis see above.

Multinucleate cells occur in some diseases - (Tzank cells herpes, Langhans cells, TB)

 

er and thats about it

 

[mr. piper]

how about downes syndrome they are humans?   aren't they?

[spudalicious]

downs syndrome is caused by trisomy of chromosome 21 (off the top of my head - it might not be number 21) anyway, they have three copies of the same chromosome. So while they're still human they have an extra chromosome