Key Area 6: Mutations Flashcards
What are mutations?
Changes in the DNA that can result in no protein or an altered protein being synthesised.
What are some characteristics of mutations?
They are normally rare, spontaneous, and rendom and most are harmful or lethal.
What is a single gene mutation?
Changes in the type, order, or number of nuclotides within a gene, causing an alteration in the resulting protein.
What can cause single gene mutations?
Substitution, Insertion, or deletion of nucleotides.
What are altered proteins often described as?
Non-functioning
What is a single gene substitution mutation?
One DNA nucleotide is swapped/substituted for another.
What are 3 examples of single gene substitution mutations?
Missense, nonsense and splice-site mutations.
What is a missense mutation?
When one amino acid is changed for another.
What can missense mutations result in?
They can either have little effect, or result in a new, non-functional protein being produced.
What is a nonsense mutation?
Where a premature stop codon is produced.
What are the effects of a nonsense mutation?
A shorter protein is produced.
What is a splice-site mutation?
Where some introns are retained and/or some exons are not included in the mature mRNA transcript.
What is an single gene inversion mutation?
They involve an extra DNA nucleotide being added or inserted into the DNA sequence.
What is a single gene deletion mutation?
They involve a nucleotide being left out or deleted from the DNA sequence.
What does both single gene insertion and deletion mutations result in?
Frame-shift
What is a frame-shift mutation?
When all of the codons and all of the amino acids after the mutations get changed. This has a major effect on the structure of the protein produced.
What is a chromosome structure mutation?
It involves a change in the structure or number of chromosomes.
What are the 4 types of chromosome mutations?
Deletion, inversion, translocation, and duplication.
What happens during a deletion chromosome mutation?
Where a chromosome breaks in two places and section becomes detached. Two ends attach to give a shorter chromosome.
What are the effects of a deletion chromosome mutation?
Effects are usually drastic as genes have been lost.
What are the effects of a chromosome inversion mutation?
Chromosome breaks in two places and the middle piece turns around so that the normal gene sequence in that part is reversed.
What is a chromosome translocation reaction?
Where a section of a chromosome is added to a different chromosome, not its homologous partner.
What is a chromosome duplication reaction?
Where a section of a chromosome is added to/from its homologous partner.
What are the effects of a chromosome duplication reaction?
These can happen without harming the individual because there is still one good copy of the gene. It may be a source of variation for the species as the extra gene may undergo beneficial point mutation. These can sometimes be detrimental, e.g. it can cause cancer.
What is the importance of mutations and gene duplications in evolution?
Duplication allows potential beneficial mutations to occur in a duplicated gene whilst the original gene can still be expressed to produce its protein.
