Alleles and Genes
Country: United States
Date: May 2005
Is nucleotide sequence of a particular gene different
between individuals of same species.For example is nucleotide sequence of
the gene expressing insulin in me different from that of other person.
At last it would be grateful, if I am provided with the email address of
the volunter scientists replying the question, so that we can interact
in future too.
For most genes, there is variability among individuals. Each different
variant is known as an allele. For the most part, the differences are
minor and many of them make no difference whatsoever. There are some
genes which appear to be identical or nearly so in everybody examined.
These genes are said to be highly conserved.
A simple way of looking at it: each individual in a species has the
same genes, but different combinations of alleles for those genes.
It depends on the protein and also the part of the protein. In beta
hemoglobin, one of the chains of the protein that carries oxygen, the cause
of sickle hemoglobin is a one letter change. The amino acids in a protein
chain fold into a 3 dimensional shape which determines what they do. A
common analogy for the way proteins and their substrates act is a lock and
key. They are shaped opposite each other. But not all of the parts of the
key are necessary to its function. The "handle" of the key isn't as
important as the shape of the part that fits in the lock. In a protein, the
part that is really important is the part that fits with its substrate. In
an enzyme, this is called the active site. So, the amino acids that form the
active site need to be the same for everyone for the enzyme (or hormone,
etc.) to work properly. Amino acids are coded for by DNA, so the DNA
sequence that codes for the active site should be the same. However, recall
that there can be more than one code for an amino acid, ie. a letter can
change and it might still code for the same amino acid. The DNA that codes
for the parts that don't form the active parts can be different for each
person and not affect the way the protein works.
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Update: June 2012