2/27 Gene Mutations Flashcards
true or false
We are all mutants
true
what is a mutation
it is a heritable change in a gene that is passed on to subsequent generations
If a nucleotide changes and is then repaired before DNA replication, is it a mutation
no, it must be heritable and be passed on
what is the beneficial aspect of mutations
they provide evolutionary changes
what is the negative aspect of mutations
they can cause disease
are all mutations good or bad
sometimes they can have no effect
what determines whether a mutation is good or bad
the selective pressure of the corresponding environment
What are single gene mutations
point mutations in DNA structure that occur within a particular gene
what are chromosome mutations
changes in chromosome structure
- gain, deletion, translocation, inversion
what are genome mutations
changes in chromosome number
What is a point mutation
it is a change to a nucleotide, it can be a substitution, insertion or deletion
What is a base substitution
it is when one nucleotide is swapped for another
what is an indel? what does it cause
an indel is an insertion or a deletion, it can cause frameshifts in the reading frame in the ribosome
are frameshifts always detrimental?
No, sometimes they can occur in non-coding areas where there is no consequence because it is not being read
what are the two types of base substitutions
transition and transversion
what is a transition base substitution
it is when there is a change within the same category of nucleotide
pyrimidine-> pyrimidine (T–> C)
purine-> purine (G-> A)
what is a G—>A substitution
transition
what is a C—> T substitution
transition
what is a transversion substitution
it is when the nucleotide is changed to a different category
pyrimidine–>purine (T—> A)
what type of substitution is C—> G
transversion
what occurs more commonly in nature? transition or transversion substitution
transitions occur in nature since they have a gentle mutation and have less of an effect on the DNA structure
Why is the ratio of transition to transversion (2:1) when there are more ways to transvert?
transition mutations keep the DNA structure uniform in its diameter.
Transversions will change the shape into an unfavorable conformation
with a transition, a purine/purine change or pyrimidine/pyrimidine change is more likely to result in what type of amino acid?
the same, usually these changes do not change the amino acid (silent mutation)
what is the lowest level of impact in point mutations
when the mutation occurs in a noncoding region or a non exon reading
true or false, every mutation has a substantial effect
false, some mutations may be in non exon genes
what is a silent mutation
it is a point mutation that results in the same amino acid
is a silent mutation considered neutral?
no, neutral refers to a type of missense mutation where the amino acid changes but there is no effect
what is a missense mutation
it is a point mutation where the amino acid gets changed
how do missense mutations affect polypeptides?
they affect the structure and function
how would an missense mutation that changes a hydrophobic amino acid to another hydrophobic amino acid affect the resulting polypeptide?
it would have a neutral affect
how would an missense mutation that changes a hydrophobic amino acid to a hydrophillic amino acid affect the resulting polypeptide?
it would likely have a drastic affect
silent mutations are due to
the degeneracy of codons
what is a nonsense mutation
it is a point mutation where a base substitution results in a stop codon
what happens if a nonsense mutation occurs near the N terminal
this results in a non functional protein that was terminated too early
what happens if a nonsense mutation occurs near the C terminal
this may result in a functional protein as the rest may be fine
what is a frameshift mutation
the insertion/deletion of 1,2 or 4+ nucleotides which changes how subsequent nucleotides are read
if we insert 3 or 6 nucleotides, how does it affect the reading frame
there is no affect because the reading frame is always read in 3s, by adding another set of 3, the regular amino acids are read correctly but the new 3 add a new amino acid
a frameshift near the N terminus will result in
a non functional protein
a frameshift near the C terminus will result in
it may be functional still
heritable changes must occur in
DNA, they must be passed on
will a mutation be detected by polymerases as errors?
no, they will be read and transcribed as usual
are RNA changes mutation?
no, changes in RNA is RNA editing and these are not inheritable and cannot be passed down
can gene mutations outside the coding sequence affect the phenotype
yes, mutations in regions like the promoter can alter how much the gene is expressed but may not change the shape of the polypeptide itself
what occurs if a regulatory element is mutated
the gene cannot be regulated properly and the amount of gene expression will be affected
what occurs if a 5’UTR or 3”UTR is mutated
the mRNA may not be able to be translated efficiently; effects gene expression quantities
what if a splice site is mutated
the introns will remain and mRNA may not be able to be spliced properly
true or false; in order to affect gene expression, every mutation must occur in an exon
false, it can be outside the exon
true or false; if you have a mutation, it must affect gene expression
false, the mutation may be in a non-translated region
what is a deleterious mutation
it is a mutation that decreases the chances of survival
what is a beneficial mutation
it is a mutation that enhances the survival or reproductive success of an organism
what is a conditional mutation
it is a mutation that only affects the phenotype under specific conditions
If you have a mutation that causes a protein to denature at high heat but is normal at low temperatures, what type of mutation is it
it is a conditional mutation
what is a wildtype
it is the most commonly found genotype
what is a forward mutation
it is a mutation that changes the wild type to some variant
what is a reversion mutation
it is a second mutation that changes the mutant back to the wild-type form
What is the difference between a reverse mutation and a reversion mutation
a reverse mutation is where the mutation changes back to the wild-type in exactly the same method that it changed originally
a reversion is a mutation that could occur anywhere by any means that leads back to the wild-type
what is a supressor mutation
it is a second mutation that counteracts the first , this is a type of reversion mutation since it brings it back to normal
What are the two types of suppressor mutations
intragenic and intergenic
what is a intragenic mutation
it is a secondary mutation that occurs within the same gene
what is a intergenic mutation
it is a secondary mutation that occurs in a different gene
if a reversion mutation occurs within the sme gene, what type of suppressor is it
it is a intragenic supression
What is an example of an intergenic suppressor mutation restoring enzymatic function?
If a mutation causes the loss of enzymatic function, a second mutation in a different protein may allow it to carry out the lost function.
A mutation in an enzyme responsible for converting an intermediate into a product results in reduced product formation. A second mutation in a different enzyme allows product formation to return to normal levels. What type of mutation is the second one?
Intergenic, because a different enzyme is compensating for the original mutation
A mutation disrupts the active site of an enzyme, leading to loss of function. A second mutation in the same gene restores enzymatic activity. What type of mutation is this?
Intragenic, because the second mutation corrects the functional defect within the same gene
You have a mutation first in gene 1, and then have a mutation at a later date in gene 2. If these two genes do not interact with eachother (independent from each other), then the second mutation can’t be considered a reverse mutation
true or false
true
if you have a second mutation in the same gene, but it does not revert it back to wild type (normal function), then this can’t be considered a reverse mutation
true or false
true
what is a somatic cell
they are body cells
if a mutation occurs in a somatic cell, will that mutation be passed onto the individuals offspring?
no, it must occur in the gametes to be passed on
if a gamete cell is mutated, will that mutation be passed on to subsequent offspring
yes
if a somatic cell is mutated earlier on in development, what is the impact of the mutation in comparison to a mutation that occurs later in a individuals life?
the impact will be greater as more somatic cell generations will be affected by it
