Episode 1:  Primate chromosomes, from 48 to 46
Channel: C0nc0rdanceAnswers
Date: 2012-01-14

I hope I've used all terms correctly, it's been a while since I've done any cytogenetics.

The question today comes from user "spylab" of Athens, Greece:
http://www.youtube.com/user/spylab/
"how did the transition from 48 chromosomes of primates to 46 of humans happen? I know that they fused but i cant understand the steps from 48 male 48 female to 46 m 46 f"
It's a great question for the first episode!

The short answer is probably a Robertsonian translocation.  The frequency of these events in modern humans is about 1 in 1000 live births.  You can start your own investigation into this phenomenon with reading the basics of translocations and the primate line chromosome fusion:

1.  Robertsonian translocations:
http://en.wikipedia.org/wiki/Robertsonian_translocation

2.  Ken Miller on the historical chromosome fusion event:
http://www.youtube.com/watch?v=zi8FfMBYCkk

3.  Proc Natl Acad Sci U S A. 1991 Oct 15;88(20):9051-5.
Origin of human chromosome 2: an ancestral telomere-telomere fusion.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC52649/?tool=pubmed


4.  Origins of primate chromosomes - as delineated by Zoo-FISH and alignments of human and mouse draft genome sequences.
Cytogenet Genome Res. 2005;108(1-3):122-38.
http://content.karger.com/produktedb/produkte.asp?DOI=80810&typ=pdfhttp://www.ncbi.nlm.nih.gov/pubmed/15545724

5.  We can reconstruct a number of chromosomal rearrangements that occurred much earlier in primate evolution:
Evolutionary descent of a human chromosome 6 neocentromere: a jump back to 17 million years ago.
Genome Res. 2009 May;19(5):778-84.
http://www.ncbi.nlm.nih.gov/pubmed/19411601