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Line 5: − + − A point mutation or ''substitution'' is the most limited type of mutation, whereby a single base [[nucleotide]] is replaced with another nucleotide. − − The sickle-cell disease is caused by a single point mutation in one allele of the beta [[hemoglobin]] gene, whereby a CCT codon is converted into TCT. The TCT then mistakenly encodes the [[amino acid]] serine instead of proline. − − Sometimes the expression "point mutation" can also include the addition or subtraction of a single base pair, which is also referred to as an "indel". − − ==Other types of mutations== Line 21:
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Some organisms will respond to harsh environments by increasing the rate of mutations. This is known as [[hypermutation]] and is hypothesized to aid organisms by creating wider variation in the [[gene pool]] of the population, increasing the chances that at least some descendents might survive under harsh conditions.
Some organisms will respond to harsh environments by increasing the rate of mutations. This is known as [[hypermutation]] and is hypothesized to aid organisms by creating wider variation in the [[gene pool]] of the population, increasing the chances that at least some descendents might survive under harsh conditions.
==Point mutations==
==Classes of mutations==
DNA is not a static entity. It is subject to a variety of different types of heritable change (mutation). Large-scale chromosome abnormalities involve loss or gain of chromosomes, or breakage and rejoining of chromatids. Smaller scale mutations can be grouped into different mutation classes according to the effect on the DNA sequence. Mutations can also be categorized on the basis of whether they involve a single DNA sequence or whether they involve exchanges between two allelic or non-allelic sequences. According to molecular pathology, there are three main classes of mutation with several subclasses: deletions, insertions and substitutions.
DNA is not a static entity. It is subject to a variety of different types of heritable change (mutation). Large-scale chromosome abnormalities involve loss or gain of chromosomes, or breakage and rejoining of chromatids. Smaller scale mutations can be grouped into different mutation classes according to the effect on the DNA sequence. Mutations can also be categorized on the basis of whether they involve a single DNA sequence or whether they involve exchanges between two allelic or non-allelic sequences. According to molecular pathology, there are three main classes of mutation with several subclasses: deletions, insertions and substitutions.
===Insertion mutations===
===Insertion mutations===
Insertion mutations are mutations where DNA is inserted into the genetic sequence.
Insertion mutations are mutations where DNA is inserted into the genetic sequence.
===Substitution mutations===
A point mutation or ''substitution'' is the most limited type of mutation, whereby a single base [[nucleotide]] is replaced with another nucleotide.
The sickle-cell disease is caused by a single point mutation in one allele of the beta [[hemoglobin]] gene, whereby a CCT codon is converted into TCT. The TCT then mistakenly encodes the [[amino acid]] serine instead of proline.
Sometimes the expression "point mutation" can also include the addition or subtraction of a single base pair, which is also referred to as an "indel".
==Mutation subclasses==
==Mutation subclasses==