chapter 15 and 17 Flashcards
mutation
variants arise from heritable genetic changes
spontaneous mutation
error in DNA synthesis (10^-8)
induced mutation
errors provoked by base analogs, radiation (10^-5)
forward mutation
change from wild type (more likely than reverse)
reverse mutation
change from mutant back to WT
mutation rate
number of mutations per cell (usually mutation per cell division)
mutation frequency
number of mutant individuals per total number of organisms in population
somatic mutations
occur in nonreproductive cells, NOT inheritable
germinal mutations
occur in reproductive tissue, can be passed onto gametes and inherited
morphological mutations
phenotypic affect
cause change in form, used to study metazoans
biochemical/metabolic mutations
phenotypic affects
used to study microbes that aren’t common
2 types of biochemical/metabolic mutations
resistance mutation (ability to grow in presence of inhibitor) and metabolic mutation (prototrophs vs autotrophs)
lethal mutation
you dead fr
conditional mutation
phenotypical, phenotypes only conferred under specific conditions (restrictive but not permissive)
DNA Level
molecular defect, insertions and deletions
Protein Level
missense and nonsense
regulatory site mutation
mutation in noncoding sequence (promotors, ribosome binding sites, splice sites, etc)
splice site mutation
DNA mutation that affect splice sites
Luria and Delbruck Experiment (1943)
e.coli resistance to T1 udes to determine if phage induced physiological change or random mutation
physiological: similar resistance in all cultures
random mutation: exponential increase in resistant e.coli
Luria and Delbruck determined
determined that mutations are random!
Luria and Delbruck issue
they grew cells in T1 which is unreliable
lederbergs (1952)
used master and replica plate to demonstrate that utations are random
mutagens
radiation, chemicals, error prone conditions
used to increase mutation rate
Selection
when you have cells that are susceptible to something and use that to pick certain cells
only MARKED cells survive
selection step by step
1) Mutagenize cells
2) spread 10^8 cells on medium with pheromone
3) recover the mutant cells that form colonies
4) determine how many genes have been identified with complimentation
screen
both WT and mutants can grow but can be PHENOTYPICALLY distinguished
screen steps
1) mutagenize cells
2) spread 10^5 cells on rich medium
3) replica plate to medium w/o leucine
4) recover colonies that don’t grow on leucine from master plate
5) determine how many genes have been identified with complimentation
large changes in chromosome structure affect…
gene position, copy number, and integrity
methods to detect chromosomal rearrangement
cytologically and genetic analysis
cytologically
viewing structures under microscope
genetic analysis
heritable phenotypes resulting from structural changes
how rearrangements occur
- chr crossing over btwn repeated sequences
- broken ends are highly reactive and bind with other broken pieces
- alterations in chr affects pairing and segregation
deletion (cytological consequence)
small deletions are sometimes viable in norm homo chr, visualized as deletion loop in meiosis
deletion (genetic consequences, homozygous deletions)
INTRAGENIC HOMO DELETE: lethal if in essential gene
MULTIGENIC HOMO DELETE: Always lethal, you dead fr
deletion (genetic consequences, heterozygous deletions 3 EFFECTS)
- phenotypes due to LOSS OF GENETIC BALANCE (dosage affect)
- Psuedodominance (expression of recessive allele in single copy)
- cannot revert to normal
adjacent duplication
next to eachother on same chr, either tandem repeats or reverse orientation
insertional dupes
located elsewhere in genome
duplication cytological consequences
looping out unpaired region in meisos when homolog pairs synapse
duplication genetic consequences
phenotypical abnormalities
inversion (cytological consequences)
inversion loops (one chr twists at the ends of the inverted part to pair with untwisted)
inversion genetic consequenes
reduction in recombo frq, partial sterility
reciprocal translocation
when non homolog chr exchange parts
euploidy
organisms with whole number multiples of n
paraploid
euploid with more than 2 sets (more than diploid)
haploid
number of chr in one gamete (n)
polyploid
multiple sets of chromosomes (common in plants)
autopolyploids
composed of multiple sets of chr from one species
autotetraploids
arise by accidentally doubling 2n to 3n by colchicine, used for commercial crops FERTILE
allopolyploids
composed of multiple chr sets from 2 highly related species
karpenchenko
got viable cabbage/raddish and fused, but bc they had different chr they were sterile (gametes are n1 + n2)
how can sterile sometimes by fertile (by chance)
spontaneous doubling of chr to even number
triploids
arise in nature by crossing 2n and 4n (usually sterile)
aneupliod
cell that lost or gained particular chr
monosomic
lost one of two homologs 2n -1
trisomic
gained extra chr so there are three homologs 2n +1
nullisomic
lost both membeers of chr pair 2n
double trisomic
2n+1+1
disomic
n+1
aneuploidy caused by __
nondisjunction
disjunction
normal separation of chr during nuclear division
nondisjunction
failure in normal separation
