Mutation & Mutagenesis Flashcards
Define mutation
Change in nucleotide sequence of gene
True or false: mutation is inheritable if reproductive cells DNA is affected
True —> natural selection
Define polymorphism
A number of non-disadvantageous mutations in the population e.g. eye colour
Define mutation rate
Rate at which DNA sequence changes
How is a mutation rate calculated
Estimates indirectly: comparing AA sequences in proteins of different organisms and time divergence with common ancestor
What is a pyrimidine
C & G bases
What is a Purine
A & T bases
What is a point mutation
A single base change in a sequence, has a tendency to back mutate
What are the 4 types of point mutation
Transitions
Transversions
Insertion
Deletion
Describe a transition mutation
A point mutation where a pyrimidine mutates to a pyrimidine or purine to purine
Describe a transversion mutation
Py to Pu / Pu to Py
Describe a deletion mutation
Deletion of a single base —> frame shift
Can also be a multi site mutation
No back mutation
Describe an insertion mutation
Insertion of a single base —> frame shift
Can also be a multi site mutation
Tends to back mutate
Many wild type microbes are prototrophic, define prototrophic
Can grow on minimal medium - more or less synthesises all of its requirements like proteins, nourishment etc.
Don’t need addition of specific compounds
Humans are auxitriohic, define autotrophic
Require addition of specific compounds
Give some examples of mutations in human disease
Sickle cell
Thalassaemia
PKU
How is mutation linked to cancer
Occurs when mechanisms maintaining normal growth rates malfunction. Due to malfunctions in tumour-suppressor genes or caretaker genes. Mutations arise after life time exposure to carcinogens
Somatic mutations can act in combination with inherited mutations to cause cancer
How are the BRCA-1/2 genes connected to hereditary breast cancer
Mutations in tumour suppressor genes, involved in repair of ds breakers in DNA, leads to them losing function thus increasing cells’ susceptibility to radiation damage.
Define recessive (trait)
Both alleles must be mutant for mutant phenotype
Usually result from mutation that Inactivated the affected gene leading to partial/carrier or complete loss of function
Define Dominant (trait)
Only one allele must be mutant. Heterozygous individuals exhibit mutant phenotype
Usually cause Gain of function (increases activity or new/inappropriate expression)
What are leaky mutations
Mutations that are never lethal because mutant protein retains some functional activity
Why does tautomerisation cause mutation
Molecule interact differently in their keto and enol forms and will bind with different bases
