Centromere question

[lanajane]

I need some clarification on centromeres. I've tried Googling, but the level of technical jargon is beyond me. Do centromeres appear at various places on the chromosome, or just where the two sides cross over/meet? In terms of the Chromosome Browser, are the centromeres represented by the gray areas as well as the narrowing areas where the two "sides" meet?

The second half of my wondering is in regard to this comment found on another message board: Speaking about Chromosome 9, "Some people have an inversion there, which can prevent recombination and cause the segment to persist longer than usual. If you have an unusual number of matches in that vicinity, that might be an explanation." I do have a large number of FF matches on Chromosome 9--all overlapping. The matches are NOT on/overlapping the centromere/center areas, however. Does anyone know anything about this Chromosome 9 inversion, or can you point me to a layman's explanation?

[GayeSherman]

Do centromeres appear at various places on the chromosome, or just where the two sides cross over/meet?

Just where the two sides meet - which varies from chromosome to chromosome.

In terms of the Chromosome Browser, are the centromeres represented by the gray areas as well as the narrowing areas where the two "sides" meet?

The gray areas are SNP-poor (not tested because they are pretty much identical from person to person). Centromeres are shown as the narrowed section.

The second half of my wondering is in regard to this comment found on another message board: Speaking about Chromosome 9, "Some people have an inversion there, which can prevent recombination and cause the segment to persist longer than usual. If you have an unusual number of matches in that vicinity, that might be an explanation." I do have a large number of FF matches on Chromosome 9--all overlapping. The matches are NOT on/overlapping the centromere/center areas, however. Does anyone know anything about this Chromosome 9 inversion, or can you point me to a layman's explanation?

I've got an area where a dozen or more matches share an approx. 8 cM segment. I don't think it's on Chr. 9 though. While I *think* I understand what an inversion is, I'd also like to see an explanation - what is it, why would it "persist", and what (if anything) can I use it for...

[mkdexter]

Here is your inversion answer in laymens terms:
http://www.familytreedna.com/faq/answers.aspx?id=17#629

It is simply a reversal of the sequence. You can have an inversion that include the centromere (paricentric) and those that do not (paracentric).

Matt.