Mutations: Difference between revisions
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[[Missense mutation|Missense mutation]] occurs through base substitution which changes a single [[Amino acid|amino acid]] in the [[Polypeptide|polypeptide]]. [[Missense mutation|Missense mutation]] can also be considered as a neutral mutation as it may not alter the function of the protein. They are not always neutral mutation and can also have a large effect on the function of the protein. | [[Missense mutation|Missense mutation]] occurs through base substitution which changes a single [[Amino acid|amino acid]] in the [[Polypeptide|polypeptide]]. [[Missense mutation|Missense mutation]] can also be considered as a neutral mutation as it may not alter the function of the protein. They are not always neutral mutation and can also have a large effect on the function of the protein. | ||
[[Nonsense mutation|Nonsense mutation]] is another mutation which can have a dramatic effect on the [[Polypeptide|polypeptides]] sequence. It affects the [[Codon|codons]] of the [[Polypeptide|polypeptide]], changing a normal codon to a [[Stop codon| | [[Nonsense mutation|Nonsense mutation]] is another mutation which can have a dramatic effect on the [[Polypeptide|polypeptides]] sequence. It affects the [[Codon|codons]] of the [[Polypeptide|polypeptide]], changing a normal codon to a [[Stop codon|stop codon]]. This causes early termination of translation resulting in a truncated [[Polypeptide|polypeptide]], which is less likely to function properly. | ||
[[Frameshift mutation|Frameshift mutation]] can also have a dramatic effect on the [[Polypeptide|polypeptide]] sequence even causing inhibition of [[Protein|protein]] function. It involves addition or deletion of [[Nucleotides|nucleotides]] which are not in multiples of three. As codons come in multiples of three, frameshift causes a completely different amino acid sequence to be read downstream from point of mutation | [[Frameshift mutation|Frameshift mutation]] can also have a dramatic effect on the [[Polypeptide|polypeptide]] sequence even causing inhibition of [[Protein|protein]] function. It involves addition or deletion of [[Nucleotides|nucleotides]] which are not in multiples of three. As [[Codon|codons]] come in multiples of three, frameshift causes a completely different amino acid sequence to be read downstream from point of mutation <ref>Robert J. Brooker, Eric P. Widmaier, Linda E. Graham, Peter D. Stilling. (2008) Biology, McGraw-Hill International Edition, New York: McGraw-Hill. Chapter 14, Page 278-283.</ref>.<br> | ||
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=== References<br> === | === References<br> === | ||
Revision as of 21:19, 9 January 2011
Mutation is the change in DNA sequence of a cell due to errors in DNA replication or during meiosis. It can also be caused by environmental agents called mutagens though induced mutation. Mutagens are physical or chemical agents that lead to changes in genetic material of an organism.
There are various types of mutations.
Point mutation is the addition or deletion of a single base pair within the DNA. It usually occurs through base substitution and even though it only causes a small change in DNA it can still have important consequences.
Silent mutation is the change in nucleotide sequence of a amino acid in a polypeptide. Even though an nucleotide sequence is changed it does not alter the amino acid of the polypeptide, this is because silent mutation only occurs in the third base of codons as genetic code is degenerate. As silent mutations does not affect the function of the protein it is considered as a neutral mutation.
Missense mutation occurs through base substitution which changes a single amino acid in the polypeptide. Missense mutation can also be considered as a neutral mutation as it may not alter the function of the protein. They are not always neutral mutation and can also have a large effect on the function of the protein.
Nonsense mutation is another mutation which can have a dramatic effect on the polypeptides sequence. It affects the codons of the polypeptide, changing a normal codon to a stop codon. This causes early termination of translation resulting in a truncated polypeptide, which is less likely to function properly.
Frameshift mutation can also have a dramatic effect on the polypeptide sequence even causing inhibition of protein function. It involves addition or deletion of nucleotides which are not in multiples of three. As codons come in multiples of three, frameshift causes a completely different amino acid sequence to be read downstream from point of mutation [1].
References
- ↑ Robert J. Brooker, Eric P. Widmaier, Linda E. Graham, Peter D. Stilling. (2008) Biology, McGraw-Hill International Edition, New York: McGraw-Hill. Chapter 14, Page 278-283.