Module 4 Flashcards
What is the chi-square formula?
o-e^2 / e
What is population genetics?
study of inherited variation within and between populations over time
What is gene frequency?
- allele frequency in a population
What is a gene pool?
- alleles in a population
What do you need to know for population genetics?
- determine the frequency of alleles and genotypes in a population to study forces that could change a population
- genotypic array
- gametic array
What is the hardy weinerg law?
- allele and geneotypic frequencies will arrive at and remain at equillibrium frequencies after 1 generation of random mating if assumptions are met
What are the assumptions for the hardy weinberg law?
- infinitely large population
- random mating
- no selection
- no migration
- no mutation
What is the genotype frequencies formula?
- p^2 (AA) + 2pq (Aa) + q^2 (aa)
What is the formula for P and q ?
f(MM) + 1/2(MN)
What does P+q= ?
1
What is fitness?
- W
- ability to survive and reproduce
- different models of relative fitness
What is directional selection?
- selection that favors one side over the other
- homozygous after an infinite number of generations
- additive effects
What is disruptive selection?
- there is a selection advantage for both extreme
- leads to bimodal population because both alleles stay in the population
- underdominance
What is stabilizing selction?
- heterozygous favored
- both alleles stay in population
- overdominance
What is variable selection?
- do they survive until reproduction
What is the variable selection formula?
P^2WAA + 2wpqAa + q^2 Waa
How fast is genetic frequency change?
very slow and small changes
around 10^-5 rate
What causes genetic frequency changes?
- mutations
What are the effects of a small population?
- genetic drift
- founder populations
- inbreeding
- bottlenecks
- non-random mating
What is genetic drift?
- random variation in gene frequency from generation to generation due to small population and sampling error
What does genetic drift lead to?
- random fixation or a loss of alleles over time
What is the founder population?
- small population that colonizes a new area
What are the problems with founder populations?
- can lead to genetic drift
allele frequencies in this population could differ from the og population - selective pressure are probably different from the population causing more rapid change because they’re are often harsher
When is inbreeing more likely to occur?
small populations
What does inbreeding cause?
- more homozygotes by descent (same allele 2x)
- affects all loci in organism
What is f?
- inbreeding coefficient
- if it is between 0 and 1 inbreeding is occuring
What is f when there is no inbreeding?
O
Does inbreeding alter allele frequencies?
no
Does inbreeding alter genetic frequences?
yes
- increases both homozygous genotype frequencies and decreases heterozygous. eventually population will al be homozygous and genotypic array will be PAA + Qaa
What is a bottlenecks?
- when a large amount of the population is killed/ It changes genetics to look like survivors
Does non-random mating change genotypes?
yes
Does non-random mating change allele frequency?
- no
What is assortative mating?
mating based on phenotype
What is positive assortative mating?
mating like individuals together results in more homozygotes but onli for loci under selction
What is negative assortative mating?
- “opposites attract”
- would keep diversity in population and results in more heterozygous for loci under selection
What is P?
- frequency of A allele in donor pop (mainland)
What is m?
- proportion of migrants after immigration occured (parent from mainland)
What is p?
frequency of A allele on island initially
What is 1-m?
- probability that a parent will come from island
What is p’?
- frequency of A allele after migration
= (1-m)p + mP
What does a change in gene frequency depend on?
- migration rate and gene frequencies of immigrants vs native
What are the types of genetic changes in a populatiion?
- emergence of a species
- divergence of a species
- extinction of a species
What are the steps to evolution?
- genetic variation starts
- increase or decrease frequency in gene pool
What is a a species?
- a group ofindividuals that could interbreed in nature
What is reproductive isolation?
- species become distinct when they don’t exchange genes
What is prezygotic reproductive isolation?
- species chose not too or can’t mate
- something like different environments
What is postzygotic isolation?
- progeny are sterile or inviable
What is the biological species concept?
- members of a species are capable of intermating and producing fertile progeny
What is allopatric specitation?
- geographic barrier intiates specitation by blocking gene flow
- example. darwins finch beaks based on available food
What is sympatric specitation?
- speciation within a single interbreeding population without a geographical barrier
- examples. hybridization leading to alloploidy or apple maggot fly
What is phylogenics?
- study of relationships between species, individuals, or genes based on charecteristics
What is the tree of life?
- shows specitation and extinction events for all life on earth
- related to phylogeny
How do you reconstruct a phylogenic tree?
- reconstruct by inferring relationships among present day organisms
What is anagenesis?
- evolution within a lineage over time
What is cladogenesis?
- splitting of 1 lineage into 2
- once cladogenesis occurs branches evolve seperately
What does cladogenesis lead to?
- more biological diversity since more species exist at the same time
What are homologs?
- related evolutionary dna sequences
What are paralogs?
- homologous sequences found in same species and arrive through gene duplication
What are orthologs?
homologous sequnces found in different species
What is an example of gene duplication?
- homeotic genes
Does the genome evolve at the same time?
- no, different parts of the genome evolve at diffferent rates
- highest mutation rates in enes that have the least effect on function
- more constraints on sequence to provide function, fewer changes tolerated bc changes might not be survivable
Do pseudogenes code for proteins?
- no
Which part of the genome has the lowest mutation rate?
- exons since introns are just removed
What is the molecular clock?
- assuming a constant mutation rate in DNA change, differences in sequence between the present day organisms can be used to date past evolutionary events
What do phylogenic trees show?
- degrees of similarities between OTUs
What are OTUs?
- operational taxonomic units based on differences in DNA sequences
- could be species, virsu strains, different alleles…
What are rooted trees?
- distance between OTUs are kown, order of divergence is inferred by comparing to an OTU out group
What is an outgroup?
- OTU that diverged earlier than all other OTUS outfroop roots the tree, all others share a common ancestor
What are unrooted trees?
- only distance between OTU is known, not order of divergenece throughout evolutionary time
What are terminal nodes?
- where we are now
What is a branch?
shows evolutionary time
What are internal nodes?
- most recent common anscestors between two
What is the distance approach?
- computing differences to infer relationships based on overall similarity of organisms typically by using multiple phenotypic characteristics or gene sequences
- doesn’t require out group
- OTUs dont need to be different species
#s are calculated from dna sequnce differences and dna sequence alignment
What is the distance approach formula?
- number of differences/ number of bases (1000)
- higher # = more differences
What are cancer cells?
- serve no useful function, unlimited potential to grow
What is pleiotropy?
- 1 gene affects multiple traits
- can be positive or negatively correlated
What are limits to selection responses?
- selection response may decline over time
- two positive traits may be negatively correlated
- extremes might not be healthy
- could lose genetic variation as homozygous are bred
How do you map quantitative trait loci?
- QTL are identified by linkage analysis between trait and molecular markers
- if the inheritance of a genetic marker is associated with the inheritance of a quantitative trait that marker must be linked to QTL
- SNPS are often markers
- looked at through GWAS
What are heritability limits?
- doesn’t say how much genes effect trait, it shows how much genes affect variation in trait
- an individual doesn’t have hertiability
- heritabliility depends on a particulat pop. in a particular environment
- if height is .8 .8 of your height isn’t genetic, it means 80% of variation is because of genetic variation
What do twin studies do?
- compare monozygotic and dizygotic twinse
What is concordance ?
in twin studies the twins are the same for the trait
What is disconcordance?
- in twins studies the twins are different for the trait
What is % concordance?
- indicates a % of twin group showing same phenotype
How does cancer occur?
- its errors occuring during cell cycle and increase through mitosis
- g1
- g 2
- m errors
- genetic but rarely heretible