Mutations Flashcards
Types of mutations
- Single gene
- Chromosome structure
What are mutations?
A change in the DNA sequence which results in phenotypic alterations. Can result in no protein or an altered protein being synthesised
When do mutations occur?
Occur naturally in every population, can occur spontaneously.
Single gene mutations
Mutation in the sequence of bases in DNA and can be described according to the effect that they have on the base sequence
Types of single gene mutations
- Substitution
- Insertion
- Deletion
Single gene- Substitution
One base is replaced with another, affects one (If any) amino acid in the encoded protein. Referred to as point mutations
Types of substitution
- missense
- nonsense
- splice site
Substitution- Missense
A change of single base pairs causes the substitution of a different amino acid in the resulting protein
Substitution- Nonsense
Substitution of a single base pairing that leads to the appearance of a stop codon in place of a codon specifying an amino acid
Substitution- Splice site
Alters the specific sequence denoting the site at which the splicing of an intron takes place
Frameshift
Insertion and deletion mutations that change the reading frame (pattern of base triplets in the DNA that is transcribed into mRNA)
Single gene- Insertion
The addition of one or more nucleotides into DNA.
Single gene- Deletion
The removal of one or more nucleotides from the DNA
Single gene- Insertion and Deletion
If it occurs in a protein coding gene it usually has a dramatic effect on the amino acid sequence of the encoded protein. All of the codons in the mRNA that appear after the mutation have changed and as a result the amino acids in the protein are also different.
Chromosome mutations
A mutation to a chromosome usually involves a substantial change to its structure so that a mutation is lethal.