multipoint runs

David Curtis dcurtis at
Thu Jun 15 05:02:03 EST 1995

NECHIPORUK at CSMC.EDU ("Alex Ext. 4983 - Medicine") wrote:

>We are mapping a disease gene.  We have four markers (A, B, C, and D)
>that are linked to the gene.  We ran two mutipoints: first, phenotype and
>A, B, and C; second, phenotype and B, C, and D.  Now here is my question:
>Does anyone knows the best and the right way to put these two runs together.
>Alex Nechiporuk,  Cedars Sinai Medical Center, Los Angeles.

I think you should plot both lines, just leaving out the tail at one
or other end. I.e. if d is the disease locus use d-A-B-C to A-B-d-C
from the first run and B-d-C-D to B-C-D-d from the second. This will
give you two overlapping lines from the two sets of lods in the B-C
interval, and you can see what you make of them. It can't be right to
use either the highest or the lowest as estimates of the "true"
multipoint lod score, and the true lod may not even lie between the
two lines. Ideally, you'd want to do a full five-point analysis using
all markers simultaneously.

Dave Curtis (dcurtis at
Institute of Psychiatry, London

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