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Flashcards in Evolutionary Forces Deck (160)
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How can evolutionary forces be seen

They must be deduced from genetic variation, fitness, phenotype, behaviour


How can evolutionary forces be studied

The forces leave signatures in the genome. This can be studied by looking into
Genetic variation of individuals (e.g. observed heterozygosity, Ho)
Comparing variation across populations (e.g. population differentiation, FST


What are the evolutionary forces

Random genetic drift
Gene Flow
Natural and Sexual selection


What are the effects of the evolutionary force mutation

Increases variation (Ho) and population differentiation (FST)


What are the effects of the evolutionary force random genetic drift

Decreases variation but increase population differentiation


What are the effects of the evolutionary force recombination

Tends to reduce variation and differentiation


What are the effects of the evolutionary force gene flow

Increases genetic variation but reduces population differentiation


What are the effects of the evolutionary forces natural and sexual selection

Depends on the selection coefficients


How do you quantify the effects of evolutionary forces

population genetics - changes in allele haplotype and genotype frequencies
quantitative genetics - changes in fitness, behaviour or phenotype
phylogenetics and macro-evolution - footprints in the genome


How do the evo forces affect natural populations

They reach an equilibrium and researchers study these equilibriums, or experiment and cause deviation


What is a gene

A gene is a piece of DNA located on a particular location of a chromosome (or a locus)


How many alleles on locus on a sexually reproducing diploid organism

There are 2 - one allele originates from the mother the other from the father (except for sex chromosomes)


What is the hardy-weinberg equilibrium model

Useful null model to predict genotype frequencies from allele frequencies


What is a population that is in Hardy-Weinberg equilibrium is called

a panmictic population


What are the assumptions of hardy-weinberg

(1) Organism is diploid
(2) Reproduction is sexual
(3) Generations are non-overlapping
(4) Mating occurs at random
(5) Population size is very large
(6) Migration is zero
(7) Mutation is zero
(8) No natural selection acting gene


What would you conclude if you found an deficit of heterozygotes AB?
32 : 16 : 2 (expected numbers)
40 : 0 : 10 (observed)

(1) Extreme inbreeding (e.g. selfing),
(2) Sampling two separate populations fixed for different alleles, and/or
(3) Underdominance (heterozygotes are less fit), (4) Null alleles


If you would find a significant excess in a particular genotype in H-W, this suggest:

Selection, inbreeding (random genetic drift), gene flow (but not recombination)


What does a mutation do

Changes the DNA, the genetic code


What are the different types of mutations

Point mutations (single nucleotide polymorphisms, SNPs)
DNA replication slippage (microsatellites)
Deletion insertions (indels or frame shift mutations)
Gene duplication and deletion
Transposable elements


What are the fitness effects of mutation

Many mutations are (nearly) neutral (~ 10%, synonymous substitutions ):
Many are detrimental (90% Non-synonymous substitutions)
Very few are beneficial (~ 1-2%)


Why do you think that non-synonymous mutations are often detrimental (or neutral)?

The original genetic code is “tested & proven” over millions of years of evolution. Hence, random improvements are extremely rare!


What symbol is used for base mutation rate?



What is the equation for the probability of an allele to stay unchanged



What are the equations for the rate of mutation over time

pt = p0(1 - μ)t


What is the mutation (genetic) load

it is the reduction in fitness caused by mutations


What is the mutation -selection balance

deleterious mutations are being generated all the time. Bad mutations are removed by selection


Are the majority of mutations recessive or dominant and what is the impact

Their (bad) fitness effects are not expressed in the heterozygote genotypes
In heterozygote condition, recessive deleterious mutations cannot be detected
Consequently, recessive mutations generally reach a higher equilibrium frequency


How to estimate mutation rate

DNA sequence divergence and split time of fossil record
Compare genome sequences from children and their parents
Mutation accumulation experiments


What is something extra to consider when estimating mutation rate

the generation time - generation times of female and males may differ


What mutation rate do researchers use in fossil record calibration and why

typically use a mutation rate of 1 × 10−9 mutations per site per year derived from the observed DNA sequence difference of ~1.3% between the human and chimpanzee and an assumed divergence time of 7 Ma based on fossil record