Genetic Mutations Flashcards
What is a gene mutation
A change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide
How often do mutations occur
Continuously and spontaneously within a population
How can a mutation in a gene lead to a change in the polypeptide it codes for
The DNA base sequence determines the the sequence of amino acids that make up a protein. Therefore, mutations in genes can occasionally change the polypeptide.
Why do most mutations not alter the polypeptide
The genetic code is degenerate
What does it mean if a genetic code is degenerate
Multiple codons can code for the same amino acid
What are the different ways that a mutation in the DNA base sequence can occur
Deletion, Insertion or Substitution
What is similar about insertion and deletion of nucleotides
Both change the amino acids that would have been coded for
What happens during a substitution mutation of nucleotides
A base in the DNA sequence is randomly swapped for a different base
What are the 3 forms of substitution mutation
Silent mutations, Missense mutations, Nonsense Mutations
What occurs during a silent substitution mutation
This mutation does not alter amino acid sequence of the polypeptide (this is because certain codons may code for the same amino acid as the genetic code is degenerate)
What occurs during a missense substitution mutation
Alters a single amino acid in the polypeptide chain
What occurs during a nonsense substitution mutation
Creates a premature stop codon (signal for the cell to stop translation of the mRNA molecule into an amino acid sequence) causing the polypeptide chain produced to be incomplete and therefore affecting the final protein structure and function
What is a deletion mutation
A mutation that occurs when a nucleotide (and therefore its base) is randomly deleted from the DNA sequence.
What generally happens after mutations
Most mutations do not alter the polypeptide or only alter it slightly so that its appearance or function is not changed
What type of mutations are insertion + deletion known as
Frameshift Mutations