Nucleic Acid Alterations
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Mutations
Genetic Engineering

Nucleic Acid Alterations

Let's look at the types of alterations that can occur to nucleic acids. These alterations can generally be categorized as being either substitutions, additions, or deletions.

This example taken from a book by Ouellette points out the nature of these three types of alterations by using a language analogy. Remember that the nucleic acid code is interpreted in codons of three units in length. So here we have a sentence that when interpreted in three-letter increments makes sense.
  THE BIG DOG SAW THE CAT
The substitution of one of the letters in that sequence (when interpreted in three-letter units) doesn't make sense, or at least a portion of it doesn't. The beginning and the end make sense, but the sentence as a whole loses meaning.
  THE BIG DOH SAW THE CAT
This shows another possible consequence of a substitution. Although, in this case, the sentence still makes sense, substitution does change the meaning of the sentence.
  THE BIG HOG SAW THE CAT
Here we have an example of an addition. A letter inserted into the sequence changes the interpretation of the rest of the sentence. The first part of the sentence makes sense but when read in three-letter segments, the remainder of the sentence makes no sense at all.
  THE BIG DOG ESA WTH ECA T
The deletion of one letter in the middle also causes the rest of the sequence of letters to make no sense and the sentence becomes meaningless.
  THE BIG DOS AWT HEC AT

 

Similarly, when substitutions, additions or deletions occur in nucleic acids, their translation into proteins may cause changes in the protein which make it nonfunctional. Or it may cause changes in the protein which cause it to have a different function. Or it may cause changes in the protein which allow it to continue to function, perhaps with no significant change in its function.

In the other pages of this section we will take a brief look at mutations and genetic engineering.

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