Are "lookalikes" genetically related??

jennifer jeanette edge jedge at students.uiuc.edu
Fri Jul 10 07:32:34 EST 1998


Hold on a second.  Just because two people look alike doesn't mean that
they have any genes in common.  There are thousands of genes that make up
appearance.  When a trait is determined by many genese it is called a
polygenic trait.  Even if these people look identical, they don't have the
same genome.  There are many parts of your DNA that are completely junk,
they don't do anything (I want to say around 98%).  So even if these two
people looked alike, there is a lot of DNA that will not be the same.

Heredity - the best definition I can give you for heritability is: A
percentage of phenotypic variation (physical appearance) accounted for by
a variation in genotype (DNA differences).  This only talks about
variation, not similarity.

I've never heard of the term convergent heredity; I have heard of
convergent evolution which is when different species were at one time
different in appearance and over time became more similar in appearance.
An example would be fish and dolphins.  Dolphins evolved from land walking
mammals, fish have always been fish.  Now, dolphins look a lot like fish.
Genetically they are no closer than back when dolphin ancestors roamed the
earth.

I'm not exactly sure where you got those equations.  Heritability can be
tricky, especially when you factor in mutations (which are normal in every
individual).  I can't go into detail, all I can say is that if you are
interested in the subject, go to a university library and check-out and
intro genetics text.

So, this guy in the shop may have been a dead ringer, but he was just as
different genetically from the 99 year old as any other stranger,

Hope this helps
Jen




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