Goldman Flashcards
What are the causes of endogenous mutations?
- chemical base change
- DNA copying errors (S phase)
- DNA repair
Why are mutations important?
- change DNA seq
- may change protein structure
- may change phenotype
- may cause variation for natural selection to work upon
What are the types of mutation?
- missense = incorrect AA
- nonsense = incorrect stop codon
- insertion = causes frame shift
- deletion = causes frame shift
- repeat expansion mutation
What causes repeat expansion mutations and can they cause problems?
- caused by primers on lagging strand, misplacing may cause repeats
- or caused by recombination between repeated seq
- can be tolerated but high no. may cause disease
What are the environmental causes of mutation?
- mutagenic chemicals –> nucleoside analogues, nucleotide mods etc.
- ionising radiation –> ds DNA breaks, eg. cosmic X rays and radon β-particles
- EM radiation –> UV light, thymidine dimers (can be reversed by certain light wavelengths/base excision repairs)
What does polymorphic mean?
- genetic locus w/ diff allelic forms in pop
What is a null allele?
- no function
How do some genetic alleles work in environmental context to create phenotype?
- many genetic disorders involve interaction w/ env
- abnormal genotype more susceptible to diseases at lower levels of env exposure
- always normal level of risk (not 0)
How can insertions (non reciprocal translocations) cause genetic variation at a chromosomal level, and will it cause problems?
- moves from 1 chromosome to another
- v rare as 3 breaks req
- wont cause problems in cell/rep as genetically balanced, if same genes then problems in segregation
Will deletions and duplications cause problems in genetic variation at a chromosomal level?
- immediate impact
- change gene dosage
- not balanced
How can reciprocal translocations cause genetic variation at a chromosomal level, and will it cause problems?
- should only happen between homologues
- problem if break w/in gene, but v low chance as most DNA non-coding
- can move promoter, causing inapprop expression
What are the causes of genetic variation at a chromosomal level?
- insertions (non reciprocal translocations)
- deletions
- duplications
- reciprocal translocations
- inversions (peri or para-centric)
Why do structural rearrangements cause problems in meiosis?
- causes chromosomes to have relationships w/ each other
When can changes to chromosome structure be neutral?
- if gene content of cell not altered
- but have consequences for reproductive health
- eg. paracentric inversion, no material lost or gained
When can changes to chromosome structure cause problems?
- if crossover in inversion loop
- decreases fertility so selected against
- bridge forms and can form dicentric and acentric chromosomes, no risk to offspring, unless divides and prod gametes
