Exam 3: Mutation and Repair Flashcards
Define mutation
An alteration in DNA sequence
Compare and contrast somatic and germ-line mutations
Somatic mutations occur in nonproductive cells and are passed to new cells through mitosis, creating a clone of genes.
Germ line mutations occur in reproductive cells and will be passed on to approximately half of the next generation who will carry it on, making it a hereditary mutation.
Compare and contrast mutations based on nucleotide alteration
Base substitutions only alter one codon.
Base insertions and deletions can alter the reading frame and can have larger effects.
Transversions
Substitution of one type of base for another.
Purine to pyrimidine or pyrimidine to purine.
A or G to C or T, etc.
Transitions
Same type of base is substituted.
Purine to purine or pyrimidine to pyrimidine.
A to G or C to T
Compare and contrast mutations based on amino acid alterations
Missense (non-synonymous) mutation: Results in new triplet code for different amino acid
Nonsense mutation: Results in triplet code for stop codon (translation terminated prematurely)
Silent (synonymous) mutation: New triplet code still codes for same amino acid
Describe the result of frameshift mutations
Result from insertion or deletion, this loss or addition causes a shift in the reading frame
Describe different phenotypical mutations
Loss-of-function mutation: Reduces/eliminates function
of gene product
Gain-of-function mutation: Results in a gene with additional function or expression not present in “wild-type”
allele. Can be enhancing or completely new.
Null mutation: Results in complete loss of function
Dominant mutation: Results in a mutant phenotype when the “wild-type” allele is also present.
Recessive mutation: Phenotype remains wild-type when the “wild-type” allele is also present
Lethal mutations
Interrupt essential process and result in death. Death can occur at various points of the life cycle.
Ex: Tay-Sachs
Conditional mutations
Dependent on the organism’s environment.
Ex: Temperature sensitive mutations
Neutral mutations
Occurs in protein-coding region or in any part of genome. Effect on genetic fitness of organism is neither beneficial nor detrimental.
Autosomal mutations
Autosomal mutations occur within genes located on autosomal chromosomes. They can still be passed down if they are found in a germline cell.
Germ-line mutations
Occur in gametes; are inherited
Spontaneous vs induced mutations
Spontaneous mutations are naturally occurring mutations that arise from normal chemical processes but tend to be rare.
Induced mutations occur in lab and occur from extraneous factors such as radiation, UV light, and natural and synthetic chemicals. Target-selected mutations include CRISPR-Cas9 and transgenics.
Replication slippage
If a loop occurs in TEMPLATE strand during replication, DNA polymerase misses looped out nucleotides, and
small DELETIONS occur on the newly synthesized strand
If loop occurs in newly SYNTHESIZED strand during replication, DNA polymerase re-replicates looped out
nucleotides, and small INSERTIONS occur on the newly synthesized strand
