Lecture 2 Flashcards
What is evolution
change in allele frequencies in a pop over time
What is evolution based on
heredity
What is hereditary
transmission of genetic info from one gen to the next
How can genetic info be transferred between people
meiosis (gametogenesis) -> sex cells
How can genetic information can be transferred between cells
mitosis
What are sources of variation
- mutation
- meiosis
- sex
Why is meiosis a source of variation
- recombination during prophase 1, exchange of portions of DNA btw homologous chromosomes
- separation of homologous chromosome pairs into different gametes
how much can recombination increase the number of possible genetic combinations
10 billion times
What is the result of meiosis
haploid gametes
What partly explains the phenotypic variability in anatomy and physiology
genetic variability
How many nucleotide base pairs in haploid human genome
3.2 billion
How many nucleotide bases are exactly the same in all humans
99.5%
How many nucleotide bases are identical between humans and chimps
98.8%
What are exons
translated into final mature RNA
What are introns
not translated into RNA but important for gene expression
What is a single nucleotide polymorphism and its relevance
depends on where it falls and whether or not it is synonymous with the original SNP
Some sections of DNA originally considered intergenic “junk” are now known to have roles as….
promoters and regulators, enhancers, spacers, and centromeres
Who is Mendel
Theory of Particulate Inheritance
What is needed for plants to be bred true for some traits
plants are homozygous for those traits
What were Mendel’s conclusions
- members of each pair of factors that control for the expression of each trait separated into different haploid gametes
- traits are inherited independently
What is phenotype
the outward manifestation of an individual’s genotype
What is genotype
The genetic configuration of the individual
What are polygenic traits
traits affected by more than one gene
What are pleiotropic genes
Genes that affect more than one trait
What are gene environment interactions
Traits influenced by both genes and the environment
What are linked traits
genes that are closely located on a chromosome
- don’t separate independently
- don’t follow a mendelian pattern of inheritance
-> linkage disequilibrium
- have a low recombination rate
What is linkage disequilibrium
term coined to describe the non-random association between alleles of genetic loci that lie in proximity to each other
Darwin’s theory of evolution and Mendel’s studies of principles of inheritance led to…
modern synthetic theory of evolution
- a way of formalizing and thinking mathematically modelling the processes and forces of evolution
What is an allele
alternative form of a gene for a given locus
What is a population
a group of potentially interbreeding individuals
What is gene pool
The entire set of alleles present in a population
What does equilibrium in hardy Weinberg equilibrium mean
no evolution - no change in allele frequencies in a population
What are the conditions for equilibrium
- no mutation
- no gene flow
- no ns
- large population size
- random mating
What are forces driving evolution
- ns and genetic drift
- reduces or redistributes variation at pop level - non random mating
- redistributes variation at population level - gene flow
- introduces or redistributes variation at population level
Selection acts on _______ but effects are seen at _________ level
individuals, population
What are different types of selection
- disruptive
- Stabilizing
- Directional
What is disruptive selection
- Selection for small and large individuals
- two peaks form
What is stabilizing selection
- selection for midsize individuals
- peak gets narrower
What is directional selection
- selection for larger individuals
- peak shifts
What is genetic drift
a random change in allele frequencies from one gen to the next based on “sampling” effect
What is an example of genetic drift
genetic bottlenecks
What is genetic bottlenecks and result
- population is reduced and then expands again
- resulting pop may not have the diversity or frequency of initial population
example of genetic drift
founder effect
What is founder effect
small subset of a larger population colonizes a new area but said subset is not representative of the allele frequencies present in parent population
Why disease causing genes are not eliminated by ns in monogenic disease
- monogenic disease (single genes)
- maintained by recurrent mutations
- deleterious effects post reproductive
- deleterious effects tend to only expressed in homozygous and/or provide advantage in heterozygous
- some alleles confer different advantages and disadvantages
- heterozygous advantage
- frequency dependent selection
- unstable environments
What are factors that can prevent HW equilibrium
- mating rules/sexual selection
- small pops
- geography
- ns
genetic drift - gene flow
- mutation
What is balancing selection
favours a balance between alleles
example of balancing selection
sickle cell anemia
Why disease causing genes not eliminated in polygenic traits
- common diseases depending on various genes each associated with an increase in the risk for the disease
- some cases disease results from specific combination of particular alleles
- or specific alleles in particular environment
Why disease causing genes not eliminated in pleiotropic traits
ex: testosterone
why within small regions people tend to look like each other and somewhat like people in neighbouring groups
- genetic similarities
- similar environmental contexts
- similar phenotypic expressions that change gradually in time and space, resulting in clines
What are clines
Geographical gradient in a particular trait across a species
How does race become biology
- using of simplistic conceptions of human biology
- equating race to genetics
- ignoring socioeconomic factors
- minimizing role of lived experiences, marginalization, discrimination, and environmental exposures
