Modifications of genes (genes mutations).

Date: 2015-10-07; view: 472.

Gene mutations or point mutations are the result of changes in the nucleotide sequence of DNA molecule in a particular region of the chromosome.

There are a variety of forms of gene mutations involving the addition, loss, change or rearrangement of bases in the gene.

In consequence of addition or loss the position effect arises. In a case if the addition or loss fragment of DNA contains quantity of nucleotides, which isn't multiple three, the sense of all nucleotide sequence, which follows after the place of mutation, is changed.

Changes of nucleotides are classified on transitions and transversions. Transversions are changes of purines (adenine, guanine) nitrogenous bases on pyrimidines (thymine, cytosine) and conversely.

Transitions are changes of purines on purines and nitrogenous bases on pyrimidines on pyrimidines.

According the results for sense of each codon (triplet) genes mutations are:

“Mix sense” mutation. At the result of mutation the sense of triplet is changed, and the triplet begin codes other amino acid.

“Sense-sense”mutation. At the result of mutation the sense of triplet isn't changed.

“Nonsense” mutation. At the result of mutation the sense of triplet is changed and the triplet transforms to nonsense codon.

There is the example of gene mutation that is the cause of sickle-cell anemia.