AQA A Level Biology: Genetic Mutation Flashcards
What is a mutation?
A change in the base sequence of DNA.
What are the three main types of gene mutations?
Substitution, insertion, and deletion.
What is a substitution mutation?
One base is replaced by another, which may change the amino acid coded for.
What is an insertion mutation?
An extra base is added, causing a frameshift that alters the reading frame.
What is a deletion mutation?
A base is removed, causing a frameshift that alters the reading frame.
What is a frameshift mutation?
A mutation that shifts the reading frame, altering all subsequent codons.
Why do substitution mutations sometimes have no effect?
Due to the degeneracy of the genetic code, the same amino acid may be coded for.
What is a silent mutation?
A mutation that does not change the amino acid sequence.
What is a missense mutation?
A mutation that changes a codon, resulting in a different amino acid being incorporated.
What is a nonsense mutation?
A mutation that creates a stop codon, resulting in premature termination of translation.
What is a mutagen?
An agent that increases the rate of mutations.
Give two examples of mutagens.
UV radiation and chemicals such as benzene.
What is a chromosome mutation?
A change in the structure or number of chromosomes.
What are the two main types of chromosome mutations?
Polyploidy and non-disjunction.
What is non-disjunction?
The failure of homologous chromosomes or sister chromatids to separate during meiosis.
What is polyploidy?
When an organism has more than two sets of chromosomes.
How can mutations lead to cancer?
Mutations in proto-oncogenes or tumor suppressor genes can lead to uncontrolled cell division.
What is a proto-oncogene?
A gene that promotes cell division, which can become an oncogene if mutated.
What is a tumor suppressor gene?
A gene that slows down cell division and repairs DNA, preventing cancer.
What is a hereditary mutation?
A mutation that is present in the gametes and can be passed on to offspring.
What is a somatic mutation?
A mutation that occurs in body cells and cannot be inherited.
How can mutations lead to genetic variation?
By introducing new alleles into a population.
