Question

Explain the different outcomes that will most likely be seen in a Base Substitution versus a Base Deletion.

Answer 1

Base substitution consequences:

a. Base substitution means replacement of one base by another. This may be transition where one purine is replaced by another purine or a pyrimidine is replaced by another Pyrimidine (A to G. G to A, T to C and C to T).  In Transversion, a purine is replaced by one pyrimidine or vice versa (A to T, A to C, G to C, G to T etc) . As in transition similar ring structure is replace (One ring structure is replace by another one ring or one two ring structure is replaced by another two ring structure), the effect is not so severe. But in transversion, one ring structure is replaced by a double ring structure or vice versa and this affect e DNA structure drastically.

DNA codes for mRNA and mRNA codes for protein. Three bases together form a genetic code which is specific for amino acid. Many amino acids have multiple codes. So if due to base substitution, genetic code is not changed for an amino acid, it is called silent mutation as change in base has no effect on protein sequence. On the other hand if base change causes change in amino acid , it is called missense mutation. Due to base substitution, stop codon may be formed suddenly and it cause premature termination of protein.

Consequences of Base deletion:

If bases are deleted, then t can change the whole set of amino acids n a protein which is called frameshift mutaton. The range of base deletion may be one base to several hundred base pairs. Depending upon the range, effect mey be different.