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13. Spontaneous or natural mutation and primary sources.
1. A mutation is a change in the DNA sequence of an
organism. Mutations can result from errors in DNA
replication during cell division, exposure to mutagens or a
viral infection.
2. Spontaneous mutations in DNA refer to changes in the
genetic sequence that occur naturally due to errors in
biological processors.
3. These mutations are not caused by an environmental factor
but occur during normal cellular processes.
4. Spontaneous mutation occurs naturally about 1 in every
million to 1 in every billion divisions and is probably due to
low level natural mitagens normally present in the
environment.
5. The primary sources of spontaneous mutations are:
1. Tautomerism:
1. Tautomerism is the relationship between two structural
isomers that are in chemical equilibrium and ready to
change into one another.
2. Generally the bases exist in keto form but at a time they can
take on either an imino or enol form.
3. Rare form of Adenine can pair with cytosine, and the end
form of thymine can pair with the guanine. These tautomeric
shifts alter the hydrogen bonding characteristics of the
bases and permits for pirine substitution or pyramidine for
pyramidine substitution.
