Population Genetics Flashcards
What was the concept that was used to identify the origin o modern humans?
That the highest level of genetic diversity is the oldest population
What is population genetics?
The study of genetic principles as they apply to entire an entire population of organisms for the purpose of understanding genetic changes that occur within and among populations
Give examples of how we can examine the genotype using phenotypic methods
Typing of ABO blood groups Electrophoresis Single Nucleotide Polymorphism Restriction fragment length polymorphism Variable number of tandem repeats
What are problems of analysing genotype via ABO blood groups?
It is a non-random sample of genes
There is alot of hidden variation
What are the problems with electrophoresis being used to examine genotype?
It is expensive and contains hidden variation
What is restriction length polymorphism?
This refers to a difference between samples of homologous DNA molecules that come from differing locations of restriction enzyme sites.
What is variable number of tandem repeats?
Uses microsatellite and minisatellite tandem repeat loci
What is a single nucleotide polymorphism test?
A DNa sequence variation occurring when a single nucleotide in the genome differs between members of a biological species or paired chromosomes
What is a population?
Any group of individuals of the same species living within a sufficiently restricted geographical area that any member can potentially mate with another member
What is the frequency of heterozygotes in a population giving the pq model?
2pq
What is the frequency of recessive homozygotes in the pq model?
Q^2
What is the frequency of dominant homozygotes in the pq model?
P^2
What are common reasons for increasing/decreasing gene frequency?
Consanguinity Selection Drift Migration Change in the mutation rate
What is the Hardy-Weinberg equilibrium?
The allele and genotype frequencies remain the same generationadfter generation if: The mating is random No selection No mutation No migration The population size is infinite
What is demonstrated by using duffy blood group analysis on the populations of iceland and greenland
The alleles are heavily weighted due ti distortion from the founders
What is the most common genetic disease in caucasians?
Cystic fibrosis
What is fitness?
A measure of the ability of an organism with a given genotype to survive and reproduce
What are the two main factors in fitness?
Viability-probability to survive to reproductive age
Fetility- mean number of offspring produced by an individual during the reproductive period
Is the dominant allele the most frequent?
Not necessarily
What is the selection coefficient?
The amount by which fitness has reduced
What are the three main types of selection?
Directional
Heterozygote Superiority
Stabilising selection
What does directional selection cause?
Population change and evolution by favouring the recessive homozygote
What is heterozygote superiority?
Where the heterozygote is favoured causing population separation which can lead to a new species
What is stabilising selection?
It causes populations to stay at their adaptive peak by favouring the dominant homozygote
What mechanisms are used to slow evolution?
Drug/pest overkill
Withholding the most powerful drugs
Vary selection over time
Screening for resistance
What is a selectively neutral substitution?
An amino acid substitution which does not seriously affect the function of the proteins
What tyoe of selection does sickle cell anaemia cause?
Heterozygote superiority
What is the rate of substitutions?
Exon < intron < intergenic flank < pseudogenes
What is the mutation rate in humans per nucleotide per offspring?
2.5 x 10 -8
What is the number of mutations per offspring in humans?
175 new mutations per offspring
What is the mutation rate in protein coding sequences for the diploid genome?
0.4
How many protein coding sequence mutations are harmful?
90%
What is genetic load?
The difference between the fitness of the theoretically optimal genotype in a population and the fitness of the observed average phenotype in a population
Where in the genome has the highest amount of mutation?
Pseudogenes
Do mutations in pseudogenes affect exons?
Only when there are huge deletions or insertions which could affect splicing efficiency
What is a molecular clock?
A method of comparing sequence homology to find when the most recent common ancestor existed
What is microevolution?
Changes in allele frequency
What is macroevolution?
Major change in genes relatively rapidly
How was the most recent common ancestor of lophotrochozoans, ecdysozoans and deuterostomes identified?
Using diversification of the Hox genes
What are the Hox genes?
A highly conserved region which determines the segmental body plan along the anterior posterior axis in embryonic development
What transformations can Hox mutants cause?
Extra digits
Change of function of limbs
What does inbreeding cause?
A steady decline in the frequency of heterozygotes
What is the frequency of AA due to inbreeding?
p + (Q/4)
What is the inbreeding coefficient?
The probability that the two genes are identical by descent
What is inbreeding depression?
The decline in performance resulted from rare recessive alleles becoming homozygous because of inbreeding
What is the effective population number?
The number of breeding individuals
What affect does directional selection have on genetic variation?
Reduces
What affect does heterozygote superiority have on genetic variation?
Increases
What affect does stabilising selection have on genetic variation?
Reduces
What affect does inbreeding have on genetic variation?
Reduces
What affect does mutation have on variation?
Increases
What affect does migration have on genetic variation?
Increases
What affect does genetic drift have on variation?
Reduces
What affect does the founder effect have on genetic variation?
Reduces
