What is Point Mutation?

As we all know that mutation is a term used to describe any change physiologically or pathologically of DNA caused by different factors of environmental conditions, stress etc. Mutations can lead to several diseases or disorder at any age of life even when a zygote transforms into a fetus.point-mutation

Mutation can be a point of a gene or can be on the whole gene or it can be frameshift.

A point mutation or single base mutation is a type of mutation that is taken place at a specific single nucleotide base of a gene, mutation can be in form of substitution, insertion or deletion of the genetic material i.e. RNA or DNA.

Frameshift is a term used when there is substitution, insertion or deletion of a pair of bases.

The least harmful type of point mutation is a substitution. Substitution only affects a triple of base pairs and its amino acids, as a result the rest of the protein is not affected. From substitution, there are 3 outcomes as follows-

  • Nonsense – the protein is useless if the amino acids that are used to be coded are changed into stop code.
  • Missense – a different amino acid is formed as a result of a change in the nucleotide. Usually, it has a little effect but can affect greatly the resulting protein.
  • Conservative mutation – amino acid change is the result of this process. However, the amino acid and its properties are not changed. A single change of amino acid and protein is not considered as a detrimental to the organism as a whole. There should be 2 or more mutation in protein or amino acid for making a functional mark.
  • Nonconservative – mutations in an amino acid that has a wild type of properties. Protein loses its function. For example sickle cell anemia it is a point mutation.
  • Silent – as the name suggests that this type is silent its effect is least on the organism and protein. It ends up with no change in amino acid coding at all.

Now as we know the substitution is least harmful but the rest 2 that is insertion and deletion are very harmful.

 

Insertion or deletion of a single base pair leads to a frameshift mutation.

1. Deletion as the name suggests that the deletion on a single base pair, in original state code is like –
TAC CGG AAT TAT ACG GCA AAA TTC ( triplets as the DNA is read as in triplets)

2. And after the deletion is made at fifth base in the second triplet the resulting frame would like this-
TAC CGA ATT CGG CAA AAT TC

Hence, as a result, there is frame shift after the deletion of a base. It affects the triple of DNA.

3. And after an insertion is made at fifth base in the second triplet the resulting frame would like this-
TAC CGA GAA TTA TAC GGC AAA ATT C

Hence, as a result, there is frame shift after the insertion of a base. It affects the triplet of DNA.

Both these mutations result in a change in frame or frameshift which is a point mutation but very harmful as it fully changes the protein.

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