Lec1: mutation rate

Question 1

Definition of mutation

Answer 1

-changes in DNA that have the potential to be propagated through DNA replication (SNPs/indels/CopyNumberVariation)

Question 2

Cause of mutation

Answer 2

Damage of molecular structure by:
* Radiation
* Mutagenic Compounds
* Free radicals etc.
Misincorporation (ie. copy error) during DNA replication
* and then the Repair mechanisms (which may have a bias) fail to restore the DNA to the original state
* Tranposable Elements insertion
* unequal crossing over/segregation problems

Question 3

mutations in germ line vs. mutation in soma

Answer 3

Mutation in germ line can be passed on, leading to polymorphism and can lead to fixation
Mutation in somatic cell aren’t passed on

Question 4

What is homologous

Answer 4

Gene that arise from a common ancestor

Question 5

Neutral theory of Evolution - Kimura & Ohta

Answer 5

• many of the common variation in gene sequence are neutral (or inconsequential) rather than adaptive
  Ie nondetrimental mutation can remain in the population

Question 6

Neutralists Idea on fixation

Answer 6

Most molecular variation that is fixed:
*is neutral (functionally/physiologically equivalent alleles)
*And therefore evolution is governed by drift
But deleterious and advantageous mutations do occur

Question 7

What is the chance of new mutation at a neutral site to be fixed

Answer 7

1/2N N is the number of member

Question 8

Selectionist model

Answer 8

Adaptive evolution explains much of the differences between Species and much of the variation within species

Question 9

Calculating mutation rate: direct measurement

Answer 9

Maintained 1000 Drosophila lines for 200+ generations
Scored electrophoretic changes in 7 allozyme loci
~(7x1000x200x2= 2,800,000 gene generations)
And found ….16 mutations!
5x10-6 mut/gene/genrn

Question 10

Calculating mutation rate: infer from divergence

Answer 10

Estimating mutation rate from divergence data:
The neutral model says: fixation rate = mutation rate(at neutral sites)

Question 11

Formula for fixation rate when infer from divergence

Answer 11

Fixation rate = 2Nµ x 1/(2N)
= µ (mutation rate)

Question 12

Calculating mutation rate by point in time of divergent

Answer 12

d=nd/n nd is the amount of divergent
d/2T= 0.2/2T
T is time
d is the number of mutations observed
If all base changes occur at an equal frequency then: d approaches 0.75
#transition and tranversion can have different mutation rates so we need jukes and cantor correction
k=-3/4ln(1-4/3d)