19.1 Mutation and variation Flashcards
Define mutation
Change in sequence of DNA bases
What are the 3 types of mutation?
Substitution, deletion and insertion
What causes the change in DNA base sequence?
Substitution, deletion or insertion of a base pair within a gene
What is point mutation?
When only one nucleotide is affected
What 3 effects can a mutation have?
- No effect
- Damaging
- Beneficial
Explain what it means when a mutation has no effect.
Organism’s phenotype is unaffected because normally functioning proteins are still synthesised
Explain what it means when a mutation is damaging.
Organism’s phenotype is negatively affected - synthesised proteins are non-functional.
Explain what it means when a mutation is beneficial.
Organism’s phenotype is positively affected
What increases the likelihood of mutation?
A mutagen
What is a mutagen?
Chemical, physical or biological agent which causes mutations
Give examples of physical mutagens. Explain how they cause mutation.
Ionising radiation e.g. x-rays.
Break one or both DNA strands - breaks can be repaired but mutation can occur during the process
Give examples of chemical mutagens. Explain how they cause mutation.
Deaminating agents
Chemically alter bases in DNA i.e. coverting C into U in DNA, changing the base sequence
Give examples of 3 biological agents that act as mutagens.
- Alkylating agents
- Base analogs
- Viruses
How do alkylating agents act as mutagens?
Methyl/ethyl groups are attached to bases resulting in incorrect pairing during replication
How do base analogs act as mutagen?
Placed into DNA in place of usual bases during replication, changing the base sequence
How do viruses act as mutagens?
Viral DNA may insert itself into a genome, changing the base sequence
What 4 processes can cause change in chromosome structure?
- Deletion
- Duplication
- Translocation
- Inversion
What is deletion in terms of changing chromosome structure?
Section of chromosome breaks off and is lost within the cell
What is duplication in terms of changing chromosome structure?
Sections get duplicated on a chromosome
What is translocation in terms of changing chromosome structure?
Section of one chromosome breaks off and joins another non-homologous chromosome
What is inversion in terms of changing chromosome structure?
Section of chromosome breaks off, is reversed and joins back onto the chromosome
