Flashcards in Mutations Deck (11):
What does 5'-->3' exonuclease activity do?
Chews away ahead of polymerase
What does 3'-->5' exonuclease activity do?
Checks for mismatches and removes them. Allows it to reincorporate the correct base pair and increases the fidelity of the DNA polymerase.
What does mutation mean?
Change in chromosome number, chromosome structure or DNA sequence
What are point mutations and give 3 examples
Single base changes
1. Mis-sense (result in a different amino acid)
2. Non-sense (result in premature termination)
3. frame-shifts (results from insertion/deletion of 1 or 2 bases)
What are larger scale mutations and give 2 exmaples?
changes of longer sequences
1. Deletions (loss of part or all of a gene)
2. Insertions (genes disrupted by insertion of large sequences)
What are the causes of spontaneous mutations?
Result of errors in replication, chemical changes to bases and insertions resulting from transposon activity
What are the causes of induced mutations?
Chemical changes by mutagens, changes caused by radiation and insertions from transposon activity
What is replication error usually associated with?
A run of bases, a base is looped out so isnt read by the polymerase
What can dinucleotide or trinucleotide repeats result in?
Insertion or deletion of 2 or 3 bases due to looping out.
What do mis-sense mutations cause?
A codon to change its codng specificity from one amino acid to another, may result in a change from a basic to acidic amino acid.