Gene Mutation Flashcards
(22 cards)
What are the double-ring purines?
Adenine and Guanine
A and G
What are the single-ring pyrimidines?
Thymine and Cytosine
T and C
What are substitutions?
Changes from one base to different nitrogenous base
SUBSTITUTIONS
What are the two types of substitutions?
Transitions
Transversions
SUBSTITUTIONS
What are transitions?
Transitions are when you go from a one purine to another purine (A and T) or one pyrimidine to another pyrimidine (C and T)
SUBSTITUTIONS
What are transversions?
Tranversion are when you go from a purine to pyrimidine, or from a pyrimidine to a purine.
What is a deletion?
The removal of nucleotides from the gene
What is an insertion?
The addition of nucleotides to the gene
We have a _____ code
We have a triplet code.
Since we have a triplet code, insertions are deletions (even of one or two nucleotides) can cause _____.
Since we have a triplet code, insertions are deletions (even of one or two nucleotides) can cause FRAMESHIFTS.
What are silent mutations?
Silent mutations - mutations in the DNA within the protein-coding region that do NOT change the amino acid sequence
These mutations have no effect on the protein.
What are missense mutations?
Missense mutations - mutations that change the nucleotide and DO cause a change in the amino acids of the protein
What are the two types of missense mutations?
Conservative
Non-conservative
MISSENSE MUTATIONS
Conservative missense
Conservative missense mutations have the original amino acid replaced with a different amino acid, but one with similar chemical properties.
Conservative changes may have little or no affect on the protein’s function.
MISSENSE MUTATIONS
Non-conservative
Non-conservative missense mutations have the original amino acid replaced with an amino acid with very different chemical properties.
These mutations are much more likely to alter the function of the protein.
What are nonsense mutations?
Nonsense mutations - mutations in the DNA that result in a premature stop codon being created within the gene
What are frameshift mutations?
Frameshift mutations are always deletions or insertions that are not multiples of 3.
Typically either 1 or 2 bases are deleted or added.
Since the genetic codon is read in triplets, these additions or deletions can completely change the amino acid sequence.
True or False:
Frameshift mutations usually destroy the protein’s function unless they occur very near the end of the protein.
True - Frameshift mutations usually destroy the protein’s function unless they occur very near the end of the protein.
What is the mismatch repair system?
The Mismatch repair system - a system of enzymes that work together to detect mismatched base pairs, remove the incorrect base, and replace it with the correct base, before S phase is completed.
Thus this system usually finds the ‘1 per million’ - mistake that gets past DNA polymerases proof reading ability.
Mistakes do happen during DNA replication but proofreading and _____ _____ keep the mistake rate down to one mistake per billion bases.
Mistakes do happen during DNA replication but proofreading and MISMATCH REPAIR keep the mistake rate down to one mistake per billion bases.
What is trinucleotide expansion?
Trinucleotide expansion - phenomenon seen for some genes that even normally have many copies of the same amino acid in the protein (and hence many copies of the same triplet codon in the gene); the many copies of the triplet make the region vulnerable to accidentally increasing the number of copies even more
When does trinucleotide expansion disease occur?
Trincuclotide expansion diseases occur when the number of copies of the triplet (and hence the number of copies of the amino acid) increases beyond an acceptable, normal range.
