centromere

by **swatkat** » Mon Mar 27, 2006 10:39 am

can a chromosome have more than one centromere?

by **LilKim** » Mon Mar 27, 2006 3:17 pm

if a chromosome is "created" with more than one centromere... This type of chromosome is very unstable it will eventually be broken and lost ... When this occurs, the cell is anneuploid and will ALWAYS die!!!

As with many things there are exceptions to this rules....

1. there are "things" called pseudo centromeres ... I guess they look like centromeres but don't act like them because one of the key centromeric proteins is absent. (can't remember the name of the protein ... i believe it's a histone protein though... This is seen in both normal people and cancer patients) ... so, these type of chromosome have one "good" centromere and one "non-functional centromere" ... therfore these chromosomes duplicate and segregate normally.

2. True Di-centrics (with 2 functional centromeres) are often seen in cancers. For whatever-unexplainable reason(???) these chromosomes can segregate normally ...occaisionally they break (resulting in acentric fragments) ... however the cell doesn't die???

(.. cancer chromosomes and cells tend to be rebellious and defy the rules!!!)

by **kitty82** » Mon Mar 27, 2006 4:37 pm

I'm pretty sure that each chromosome just has one centromere, hey take a look the picture of chromosome you'll see ...

by **swatkat** » Tue Mar 28, 2006 5:54 am

ok
thx
just out of curiosity
and yes kitty82
i have seen the picture of the chromosome plenty of times

thx lilkim
that info on cancer cells was very interesting

by **sdekivit** » Thu Mar 30, 2006 5:46 pm

in a robertsonian translocation actually a dicentric chromosome is created, but they act as one centromere.

by **swatkat** » Fri Mar 31, 2006 10:15 am

whats a "robertsonian" translocation??

by **sdekivit** » Fri Mar 31, 2006 1:09 pm

search for it on google

by **swatkat** » Fri Mar 31, 2006 6:32 pm

ok..

i did find it on google
just one thing.....
the balanced and unbalanced forms of the acrocentric chromosomes are decided by the position of the centromeres,right?

by **LilKim** » Sun Apr 02, 2006 1:56 am

balanced means that no genetic information was lost or gained during a chromosomal rearrangement.

Unbalanced refers to if some DNA is added or deleted ... resulting in an "unbalanced genome" ... (Examples of unbalanced genomes and disease: turner syndrom=monosomy X or Down syndrome = +21)

However, with a classic robertsonian (when 2 centromeres fuse) no DNA is lost or gained... and this is considered Balanced.

centromere

centromere

hi

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