How can a base sequence be mutated?

Answer 1

It would all involve the protein's structure that the gene is responsible for. There are 4 levels to a protein's structure- primary, secondary, tertiary and quaternary. It would essentially boil down to the primary structure. The primary structure is just the amino acid sequence that the gene codes for.

Most importantly, there are several types of mutations. A single base change is called a point mutation. The genetic code of As,Ts,Cs and Gs code for specific amino acids in groups of 3 called codons. With 64 combinations and only 21 amino acids, there are duplicate codes. Let's take a silent mutation which is harmless. Let's say TTT is mutated to TTC. The RNA molecule that is transcribed will still code for the Phenylalanine amino acid. No change will occur to the organism.

Now a damaging type of point mutation could be a missense mutation. If TTT is mutated to TTA, Phenylalanine will become the Leucine amino acid. This effect on the protein's primary structure can affect the secondary structure (alpha helixes or beta sheets), tertiary structures (3-D shape) and\or the quaternary structure (which is when several proteins combine. This structure is not always necessary). Sometimes a missense mutation isn't so bad.

Very damaging, single base mutations include insertions, deletions and nonsense mutations. In a very short explanation, there are 3 types of codons that stop a gene's transcription. If, along the gene's code, one nucleotide is inserted or deleted or changed to code for TAA, TGA or TAG at another place along the gene, the amino acid sequence will be too long or too short. This again will affect the higher levels of protein structure.

If a sequence of bases are altered, it can be just as damaging. Examples are "Amplifications" which lead to multiple copies of all chromosomal regions, increasing the dosage of the genes located within them. "Deletions" of large chromosomal regions lead to the loss of the genes within those regions.

Any type can lead to cancer. I'm majoring in molecular Biology and genetics and I find this very interesting so I hope it helps.

Answer 2

By changing one base pair to a different base pair, by inserting a base pair or more than one base pair, by deleting one or more base pairs.

Answer 3

mutation