Talk:Recombination frequency

Discussion about Rf and centimorgans
(pasted from Centimorgan page during merge Dr d12 17:17, 7 December 2006 (UTC) )
 * A 50 cM distance means that the genes will reassort 50% of the time, which makes them unlinked.

This doesn't sound right to me. If two genes are 50 cM apart, the probability that they are exchanged is the sum of the odd numbered points in a Poisson density with λ=0.5, which is 0.316. -phma 02:14, 23 December 2005 (UTC)


 * A cM is a map unit, 50 map units = unlinked. Sounds right according to my notes, but I'll look around when I can get to my books again.  --  stillnotelf   has a talk page  03:04, 23 December 2005 (UTC)

I get a different result using Excel. In cell C1 I put 0 (the chance a single gene will unlink from itself). Then I used the formula =(C1*0.99)+(1-C1)*0.01 to determine the chance that a gene 1 cM away will unlink ((the chance it was unlinked) * 0.99 + (the chance it was linked) * 0.01). Then I copied the formula 49 more times and in cell C51 I got the result 0.31791516. I don't know that much about statistics, but the discrepance could be because either:
 * 1) Excel doesn't have infinite resolution. Meaning my number is wrong,
 * 2) because I was doing 50 descrete checks, not checks on a continuum. Meaning my number is correct or,
 * 3) my error somewhere else

I'd be happy to be corrected. --Djfeldman 17:19, 12 July 2006 (UTC)

Use of parent unit
"The size of the canine genome was initially estimated from maximum likelihood predictions to be 27 morgans in genetic distance." PLoS Genetics 1(5), 2005. No shortage of other examples...

"A 50 cM distance means that the genes will reassort 50% of the time, which makes them unlinked. "

This is incorrect. Two genes located 1 cM apart will by definition result in an observed recombination frequency of 1%. Over small intervals, x cM is almost identical to a recombination frequency of x%, but for two genes located wider apart, the observed recombination frequency will be lower than the genetic distance in cM, due to double crossing-over events. Two approximation functions are commonly used to adjust for this, the Kosambi and the Haldane functions. So: recombination frequency is NOT identical to genetic distance in cM. AND, all human chromosomes except the Y chromosome are larger than 50 cM.

Requested move

 * The following discussion is an archived debate of the . Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section. 

Survey and discussion
Please add * Support  or  * Oppose  followed by an optional brief explanation, then sign your vote using "&#126;&#126;&#126;&#126;".
 * Support, but with lowercase "f" (i.e. Recombination frequency). David Kernow 11:57, 13 June 2006 (UTC)
 * Support, in agreement with lowercase "f". Hoo-rah for typos! Eurisko97 03:06, 14 June 2006 (UTC)


 * The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Oppose merge "Linkage" is a much more familiar term. It shouldn't be stuck inside an article on Recombination frequency, which fewer people would go to look up. Sfahey 02:58, 9 December 2006 (UTC)

(Confusion)
There is confusion here between --Henri de Solages 17:27, 15 December 2005 (UTC)
 * recombination frequency,
 * recombination rate,
 * genetic distance.

Yes, in fact in 20+ years I never heard the term "recombinant frequency". Recombinant fraction - yes. Recomination frequency - yes. Otherwise, no. Give it a few days, but then I will butcher this. Any objections, let me know. Ben Carritt 17:54, 2 January 2006 (UTC)

Definition
The beginning poorly defines recombination frequency - its not "when crossing over takes place". Look at the wording, FREQUENCY. It is a mathematical number relating to how often something (recombination) occurs. Unfortunately for me, I don't know exactly what recombination is defined as, will someone please give me the reader's digest version of the defintion?Tourskin 22:08, 12 May 2007 (UTC)