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!!!)

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

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

search for it on google 😉

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.