Unit 1-Mutations Flashcards
What is a mutation?
Mutations are changes in the DNA that can result in no protein or an altered protein being synthesised.
Mutations can have which two results?
No protein is expressed
or
an altered protein is expressed
Are mutations rare and random?
Yes
What are mutations the only source of?
Mutations are the only source of new variation in populations.
What is a mutant?
An organism that has been affected by and is the result of a mutation.
What are the two main types of mutation?
Single gene mutations and chromosome structure mutations.
What do single gene mutations involve?
A single gene mutation involves a change in the number or sequence of bases in a gene.
What are the three types of gene mutation?
Substitution
Insertion
Deletion
What happens in a substitution mutation?
One nucleotide is exchanged for another.
What happens in an insertion mutation?
One or more nucleotides added into a DNA sequence
What happens in a deletion mutation?
One or more nucleotides removed from a DNA sequence
Substitution mutations can be described as a point mutation.
What does this mean?
Point mutations only affect one codon
What are the 3 outcomes of substitution mutation?
Missense, Nonsense and Splice-Site.
What is meant by a Missense mutation?
Missense mutations result in one amino acid being changed for another.
What is the effect on the protein from a Missense mutation?
May result in the shape of the protein changing or may not have any significant effect
What is meant by a Nonsense mutation?
A mutation which results in a codon for a specific amino acid being changed to a stop codon.
What is the effect on the protein from a Nonsense mutation?
It causes a shorter protein being produced.
What is meant by a Splice-Site mutation?
The boundaries between exons and introns are affected (splice sites).
What is the effect on the protein from a Splice-Site mutation?
The protein does not function properly.
Insertion and deletion mutations can be described as frame-shift mutations.
What is meant by this?
They affect every single codon after the mutation.
Completely different amino acids are coded for from this mutation onwards.
What is the effect on the protein from an Insertion mutation?
Every amino acid after the mutation is affected so the protein is usually non-functional.
What is the effect on the protein from a Deletion mutation?
Every amino acid after the mutation is affected so the protein is usually non-functional.
Why can the broken end of a chromosome join to another broken end?
The broken end of a chromosome is ‘sticky’.
What are the 4 types of chromosome structure mutations?
Deletion
Duplication
Inversion
Translocation
What happens in a deletion chromosome mutation?
Deletion is where a section of a chromosome is removed.
What does a translocation mutation involve?
Translocation is where a section of a chromosome is added to another chromosome that is not its homologous partner
What happens in an inversion mutation?
Inversion is where a section of a chromosome is reversed.
What happens in a duplication mutation?
Duplication occurs when a section of a chromosome is added from its homologous partner.
Why can chromosome structure mutations be so lethal?
They often involve such a substantial change to the structure of the chromosome.
Mutation occurs continuously and can be spontaneous.
Give an example of something that can cause mutations?
ionising radiation (gamma rays, X-rays and UV light) or chemical mutagens such as tar from cigarette smoke
