Mutations and Fitness Flashcards
What are the 3 causes of point mutations?
UV damage
DNA breaks
Polymerase error
What are the 5 ways you can fix a point mutation?
Polymerase proofreading
3’ to 5’ exonuclease (dnaG)
Base Excision Repair (BER)
Nucleotide Excision Repair (NER)
Methyl-directed Mismatch Repair (MMR)
Loss of function mutations are dominant or recessive?
Recessive
What are the 3 loss of function mutation classes?
Null
Hypomorph
Frameshift
What are the 3 gain of function mutation classes?
Hypermorph
Dominant negative
Neomorph
Gain of function mutations are dominant or recessive?
Dominant
Dominant negative mutation
Gene prevents a WT protein from preforming (constitutive activation is a subtype)
What are the 2 causes of insertions and deletions?
Pol 3 slippage
Recombination
Explain pol 3 slippage
Inserts or deletes a single nucleotide when either the newly synthesized strand loops out (inserts) or the template strand loops out (deletes)
Explain recombination induced indels
Homologous repeats meet. Plasmid is lost in a pure deletion. Fragment is moved in an insertion and thus deleted from its original place.
Inversions vs indels
With inversions the gene order and direction is reversed
Translocations
Homology leads to movement of a fragment
Transposition
Movement of a transposon via transposase (tnp)
Describe transposon structure
Direct repeats (same way) and inverted repeats are on either side of tnp (or more) gene(s)
Explain how CRISPR works
2 RNAs are produced and hybridize
Cas9 is a nuclease that along with RNase3 processes the RNA hybrid
Cas9-RNA-hybrid scans for homologous RNA with a PAM
Homologous RNA cleaved
What does CRISPR do?
Defense against viruses and transposons
Nonmethylated invading DNA is targeted by Cas1 and Cas2 guided by a PAM sequence
This makes spacer DNA which is sorta like bacterial memory B cells
How do we use CRISPR?
Mutate region of interest randomly with no repair template and NonHomologous End Joining (NHEJ)
OR
You can synthesize a repair template to guide exactly how the DSB is fixed to introduce a specific mutation
True or false: most mutations will never be observed due to selection and multiple competent sub populations
True
What are the 3 evolutionary effects of mutations
Detrimental
Neutral
Beneficial
True or false: mutations can only be spontaneous, not induced by selection
False, they can be both