Point Mutation
Definition
A change in a single nucleotide in the DNA sequence. A transition substitutes one purine for another or one pyrimidine for another (A-T to G-C or vice versa). A transversion substitutes a purine for a pyrimidine or vice versa.
- Scope
- Single-nucleotide DNA change
- Transition
- Purine-purine or pyrimidine-pyrimidine swap
- Transversion
- Purine-pyrimidine swap
Common questions
Why are transitions more common than transversions in most genomes?+
Transitions arise more readily from common chemical processes such as spontaneous deamination and DNA polymerase error patterns, while a transversion requires a larger structural change to the base pairing, which is why observed mutation spectra are usually transition-biased.
How does a point mutation matter in forensic DNA typing?+
A point mutation at an STR flanking region or a mitochondrial control region site can create or remove a primer binding site or a polymorphic marker, occasionally producing null alleles or a heteroplasmic-looking result that an analyst has to distinguish from a genuine mixture or mismatch.
Related terms
- DNA Polymerase
- The enzyme that synthesises new DNA by adding deoxyribonucleoside triphosphates complementary to the template strand. In humans, polymerase delta copies the lagging...
- Frameshift Mutation
- A change in the reading frame of a coding sequence caused by an insertion or deletion of a number of nucleotides that...
- Okazaki Fragment
- A short segment of DNA (100 to 200 nucleotides in eukaryotes) synthesised on the lagging template strand in the 5-prime to 3-prime...
- Semi-Conservative Replication
- The mode of DNA copying in which each daughter double helix retains one parental strand and acquires one newly synthesised strand, confirmed...
- Short Tandem Repeat (STR) Slippage
- Replication slippage at a repetitive locus where the template and nascent strands temporarily misalign. If the nascent strand slips forward, one repeat...