how many markers?

Alex Ext. 4983 - Medicine NECHIPORUK at CSMC.EDU
Fri Jun 30 16:20:16 EST 1995

>what is an easy way to estimate the number of markers needed to map a 
>genome at a given interval.  i'm just looking for something quick and 
>dirty.  also, my advisor says that, theoretically, one chromosome arm 
>should equal 1 Morgan.  is this valid?  there are published linkage 
>groups out there that are over 100 cM!  that's 10 Morgans!  thanx in advance.

Get a paper by Michael Boehnke published in 1994 in Am J Hum Jenet (summer 
I think).  That will answer all your question.  It will be hard to read 
if you do not know much about math., but he has some tables which will be 
very helpful for you.  In a couple words: number of markers that you need for a 
random genome scan depends on the number of informative meioses that you 
have on hand (if you do not know that number you will find the formula in
Boehnke's paper), and also the level of certanty that you want to achieve.
For ex. if you want to be at 90% the spacing between markers will be smaller
than at 50%.  In general you will find out that number of markers that you 
will need ranges from 150 - 250.  
Good luck,
Alex Nechiporuk
Cedars Sinai Medical Center, UCLA.

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