MUTATION

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The term mutation is derived from the Latin word “mutare” – which means “to change”. Thus, mutation is simply defined as the change in genetic makeup (genotype) of an organism which results in the transformation of the phenotype of the organism. Mutation is an inheritable change in the base sequence of the genome of an organism. It usually occurs in the gene or DNA of an organism. Mutation is the change in the base sequence of the DNA. Mutant genes are genes that have undergone mutation. When mutation occurs, it results to the production of an organism or phenotype whose gene or DNA has been altered and made different from the original genetic makeup of the parent cell or organism. Such an organism with altered DNA or gene is called a mutant.

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A mutant is an organism whose genome carries a mutation. Mutation is a stable, heritable change in the DNA or gene of an organism. Such an alteration in the organism’s nucleic acid molecules (DNA or RNA) eventually results in the production of a novel phenotype. Mutation can occur in any of two ways: either spontaneously or as a result of a mutagen. A mutagen is any physical, biological or chemical agent that promotes or cause mutation in an organism. Typical examples of mutagens include UV rays, ionizing radiations, and heat (which are all physical mutagens). The chemical mutagens include but not limited to intercalating agents, alkylating agents, bisulphite and nitrous acid. Mutagens alter the base sequence of nucleic acid molecules in such a way that wrong pairing of nucleotide bases during DNA replication may occur. These wrong pairing of nucleotide bases eventually results in the production of mutants.

Mutagenesis is defined as the generation of one or more mutations in an organism. Mutations can either be harmful or beneficial in a living organism. Beneficial mutations usually result in the production of phenotypes with enhanced metabolic activity. This type of mutation mainly results in the production of novel organisms. Evolution in living organisms is usually driven by beneficial mutation since it results in the production of different varieties of species of the same organism. In harmful mutation, the change in the DNA of the organism undergoing the mutation usually results in the production of phenotypes with decreased metabolic activity. There is usually the loss of the ability to perform or carry out certain activities in such mutants. An alteration in the amino acid sequence may adversely affect the function of a particular protein in the organism. Such a change that affects protein function is regarded as a harmful mutation.

Further reading

Cooper G.M and Hausman R.E (2004). The cell: A Molecular Approach. Third edition. ASM Press.

Das H.K (2010). Textbook of Biotechnology. Fourth edition. Wiley edition. Wiley India Pvt, Ltd, New Delhi, India.

Davis J.M (2002). Basic Cell Culture, A Practical Approach. Oxford University Press, Oxford, UK. 

Mather J and Barnes D (1998). Animal cell culture methods, Methods in cell biology. 2rd eds, Academic press, San Diego.

Noguchi P (2003).  Risks and benefits of gene therapy.  N  Engl J Med, 348:193-194.

Sambrook, J., Russell, D.W. (2001). Molecular Cloning: a Laboratory Manual, 3rd edn. Cold Spring Harbor Laboratory Press, New York.

Tamarin Robert H (2002). Principles of Genetics. Seventh edition. Tata McGraw-Hill Publishing Co Ltd, Delhi.     

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