lecture 6

Question 1

mutation rates in humans?

Answer 1

• Average mutation rate for a single site: 2.3 x 10^-8 per base pair generation (very low)
  ○ Even lower for frameshifts
  ○ Exact rate varies across the genome and across different species
  
  • Our genome has hot spots where the frequency of mutations in higher

Question 2

what mutations are more common?

Answer 2

• Transitions are more common than transversions and indels have an even lower mutation rate
  
  • Mitochondrial dna has a higher rate of mutations

Question 3

what is the simple mutation mode?

Answer 3

• The rate represents the probability of a mutation per locus per generation
  Estimation over a long period of time
  is the probability of A mutating into a then
  (1 - u) is the probability of A not mutating

Question 4

mutation rate formula

Answer 4

pt=po(1-u)t

Question 5

what is a reverse mutation

Answer 5

• • Will go back to original form
    U represents a reversible mutation

Question 6

why are irreversible mutations more common

Answer 6

• Most protein-coding genes have a forward mutation rate (wildtype to
  mutant) that is at least an order of magnitude greater than the reverse
  mutation rate (mutant back to wildtype).
  ○ More common to be irreversible
  ○ Various kinds of changes anywhere along the gene can result in loss of gene
  function, but once a gene has mutated, only very specific kinds of reverse
  mutations will restore function

Question 7

what does humans relationship to primates suggest

Answer 7

• The fact that human populations are more closely related than populations of the other primates suggests that human evolution processes (gene flow and admixture) had a comparatively greater role than long term isolation and differentiation
  ○ Lots of mixing of populations in humans
  ○ Humans tend to have longer reproduction periods and produce less offspring compared to other organisms
  Hard to follow along mutations and mutation rates AND specifically, reversible mutations

Question 8

ex of beneficial mutation

Answer 8

• Some mutations can be beneficial
  
  • Ie elephants - live longer + bigger body size - why don’t they have more mutations?
    Have tumor suppressing genes

Question 9

Why are mammoths extinct ex

Answer 9

• Why are mammoths extinct
  ○ Mutation leading to Loss of olfactory receptors - may have reduced population numbers - important for detecting others + impacted urine detection - less mating, less status in finding a suitable mate
  ○ Also a mutation that lead to an unusual translucent coat
  Not 100% understood, these are just theories