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SECTION 1
Introduction SECTION 2 SECTION 3 HGP SECTION 4
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Your DNA and the DNA of every organism is made up of these same four bases. They are just arranged in different orders to provide the secret code of life. This is very similar to the way our alphabet works. Read the following two sentences and
visualize in your mind what each of these looks like.
Only one letter in our code was changed, but the meaning of the sentence has changed. The same is true of our DNA.
To read the DNA, the 2 strands must separate.
We will read the bottom strand.
The following 2 “sentences” of DNA were taken from 2 different people.
Person
A ggc agt gtg tat gca ggc atc ctc agc tac ggg gtg ggc cct
Person
B ggc agt gtg tat gca ggc atc ctc agc tac agg gtg ggc cct
Just like changing the “c" in cat to a “b” gives you a very different image, changing a “g” in person A to an “a” in person B has a different end result. In DNA the sequence of letters codes for a protein. Different sequences code for different proteins. Proteins are used by organisms for numerous important processes. Your hair is a protein. The enzyme in your spit is a protein. The hormone that helps you grow is a protein.
So in English
The DNA sequence given above is part of the code for a human growth protein. Just like DNA is made up 4 different subunits (ATCG), proteins are made of 21 different subunits called amino acids. Scientists use a different letter from the alphabet to represent each of these.
Take a look at the DNA code and the protein code for both person A and B.
Person
A’s DNA ggc agt gtg tat gca ggc atc ctc agc tac ggg gtg ggc ttc
codes
for the amino acids G
S
V
Y
A G I
L
S
Y G
V
G F BUT Person
B’s DNA ggc agt gtg tat gca ggc atc ctc agc tac agg gtg ggc ttc
codes
for the amino acids G S V Y A G I L S Y R V G F
If
we were to look at the whole DNA code for just this one protein (this is
what we call a gene) and then
the protein
that it codes for, the protein sequence would be like the one you see
below for
person A. Person B would
exactly the same except the one G in line 8 is switched to
R.
This doesn’t seem like a big deal. But if you are a cat, you aren’t a bat and you can’t fly. If R was put in instead of G, the results in person B are dramatic. This person will suffer from a form of dwarfism. Dwarfism is characterized by an average-size trunk, short arms and legs, and a slightly enlarged head and prominent forehead. Adults, on average, are only four feet tall.
Please extend your knowledge of
the
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glycine
