BOW 2 Mutations

Biology BOW
Describe the different types of mutations: sense, non-sense, deletion, insertion, framshift, point and translation.


Sense mutation: A mutation that results in a new codon still coding for the same amino acid in a polypeptide or protein. Usually due to a substitution mutation.

Non-sense mutation: A mutation that results in transcription of a nonsense codon and terminates the polypeptide or protein prematurely.

Deletion mutation: a mutation in which a part of a chromosome or a sequence of DNA is missing.   Deletions can be caused by errors in chromosomal crossover during meiosis. This causes several serious genetic diseases. Deletion also causes frame shift.

Insertion mutation:  the addition of one or more nucleotide base pairs into a DNA sequence. This can often happen in microsatellite regions due to the DNA polymerase slipping. Insertions can be anywhere in size from one base pair incorrectly inserted into a DNA sequence to a section of one chromosome inserted into another.

Frameshift mutation: a genetic mutation caused by indels (insertions or deletions) of a number of nucleotides that is not evenly divisible by three from a DNA sequence. Due to the triplet nature of gene expression by codons, the insertion or deletion can change the reading frame (the grouping of the codons), resulting in a completely different translation from the original. The earlier in the sequence the deletion or insertion occurs, the more altered the protein produced is.

Point mutation: or single base substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA.

Transition mutation: a point mutation that changes a purine nucleotide to another purine (A ↔ G) or a pyrimidine nucleotide to another pyrimidine (C ↔ T). Approximately two out of three single nucleotide polymorphisms (SNPs) are transitions.Transitions can be caused by oxidative deamination and tautomerization. Although there are twice as many possible transversions, transitions appear more often in genomes, possibly due to the molecular mechanisms that generate them.