Mutations Flashcards
Define mutation.
A change in DNA sequence that affects genetic information.
When do most mutations occur in the cell cycle?
During DNA replication - interphase.
What are the 3 steps in DNA replication?
Initiation.
Elongation.
Termination.
What happens during initiation?
DNA helicase unwind the DNA by breaking H-bonds.
What happens during elongation?
New DNA strand ‘grows’ 1 base at a time with the primer acting as the leading strand’s starting point.
What happens during termination?
Fragments terminate in an RNA primer and are removed by DNA exonucleases. Complementary nucleotides are added to the gaps.
What enzyme is involved in initiation?
DNA helicase.
What enzyme is involved in elongation?
DNA polymerase (it controls elongation).
What enzymes are involved in termination?
Primase produces the primers needed. DNA exonucleases remove fragments. DNA ligase adds phosphate to gaps.
1 chromosome
=
1 chromosome
2 chromatids
What is produced during mitosis?
2 identical daughter cells.
What is produced during meiosis?
4 differing haploid daughter cells.
What are the 2 types of substitution mutations?
Transitions and transversions.
What is a transition mutation?
A substitution mutation where a purine is swapped for a purine or a pyrimidine for a pyrimidine.
What is a transversion mutation?
A substitution mutation where a purine is swapped for a pyrimidine and vice versa.
What is the difference between missense, nonsense and silent mutations?
Missense results in an amino acid change, nonsense results in a STOP codon and silent has no amino acid change.
Missense mutation
=
Missense mutation
Nonsynonymous substitution
Silent mutation
=
Silent mutation
Synonymous substitution
Where does the term nonsynonymous substitution come from?
Because there is a change in the nucleotide but no change in the
What is an example of a point mutation in disease? What is the specific change?
Sickle cell disease. Thymine is replaced by adenine leading to a synonymous substitution - Glu changes to Val.
What 5 mutations cause frameshift?
Insertion, deletion, duplication, inversion and translocation.
What is an example of a frameshift mutation in disease? What is the specific change?
Tay Sachs disease. A 4 nucleotide insertion on chromosome 15.
