see evidence of it in the phenotype.
When we think about doing a genetic map, we
know that we have all of our linkage groups,
each chromosome. So humans, we have 23
different linkage groups of 46 chromosomes
because they come in pairs. We can obtain
linkage data based on crosses and this was
done a lot in fruit flies in order to perfect
the technique of genetic mapping. You have
to keep in mind that genetic mapping is relative
distance based on these recombination frequencies.
Nothing is actually being measured. We are
going to look at the percent recombination
to give us an estimate of the distance apart
two genes are on a chromosome. Here is an example
of looking at those crossing
over events, we might see those crossing over,
we can draw them as simple lines. I like
to do that to keep track of things while I
am calculating recombination frequencies and
we call these units, these percent recombination
either a map unit or a centimorgan. Let us
say we run into 30 percent recombination, we
can say it is 30 centimorgans from the other
allele or we could say that it is 30 map units.
Those things are exactly the same, measurement.