Week 3: Genetic Variation Flashcards
What is Mendel’s Law of Segregation?
Each individual has two gene copies at each locus and these gene copies segregate during gamete production so only one gene copy goes into each gamete. Also concluded purple color was dominant to white which was recessive.
What is Mendel’s Law of Independent Assortment?
Which allele is passed down to the next generation at one locus is independent of which allele is passed down to the next generation at another locus. This only holds true for genes on diff chromosomes - unlinked loci and not for linked loci.
What is blended vs. particulate inheritance?
Darwin viewed heredity as a blending process. Mendel’s theory suggested particulate. While phenotypic effects of the particles carrying heritable info may blend, the particles remain distinct and can be separated again in future reproduction.
What are regulatory elements? Cis vs. trans? Enhancers vs. silencers?
Regulatory elements influence rate at which RNA is transcribed - affecting levels of gene expression and phenotype. When they affect genes at nearby sites on same chromosome - cis regulatory elements. Trans regulatory elements - modify expression or activity of genes on diff chromosome - often by encoding soluble proteins that can act at remote DNA locations.
Enhancers- increase transcription rate
Silencers - decrease transcription rate
What is the role of epigenetics?
Many epigenetic mechanisms involve secondary modifications to DNA molecule or histones. ie. DNA methylation - methyl group to C-G base pair in DNA. Highly methylated regions are inaccessible to RNA polymerase and are unexpressed.
Epigenetic changes play roles in development. One in cell differentiation - driven by methylation patterns and histone modifications. Also X chromosome inactivation - methylation of histones. Epigenetic modifications in prenatal development are responsible for aspects of developmental plasticity - adjustment of phenotype to suit environment.
What is a transition vs. transversion?
Most basic form of mutation is single base change. When purine is replaced by purine or pyrimidine by pyrimidine ie is a transition. When purine replaces pyrimidine or vice versa it is a transversion. Transitions generally occur more often.
What is chromosomal fission vs. fusion?
Can break apart into new stable configurations - chromosomal fission or fuse to create new ones - chromosomal fusion.
What are distribution of fitness effects?
frequencies of mutations with various fitness consequences are becoming available. Scientists estimate effects by creating mutants and assessing their fitness.
frequencies of mutations with various fitness consequences are becoming available. Scientists estimate effects by creating mutants and assessing their fitness.
What is population genetics? What are quantitative vs. qualitative predictions?
investigates how genotype frequencies in offspring population.Can look at evolutionary process in qualitative terms. ie. coat colour. Quantitative predictions can be made - genotype frequencies. Steady-state frequencies - equilibria of models
What are the 3 conclusions of Hardy-Weinberg?
- Frequencies of A1 and A2 alleles do not change over time in absence of evolutionary processes acting on them. 2. Given allele frequencies and random mating, we can predict the equilibrium genotype frequencies. 3. if no evolutionary processes are operating, a locus that is initially not at Hardy-Weinberg equilibrium will reach it in single generation.
What are the assumptions of Hardy-Weinberg?
- Natural selection is not operating on trait
- Is no assortative mating - is random with respect to locus.
- No mutation is occurring
- There is no migration in or out of population
- The population is effectively infinite in size - genetic drift is negligible.
What is Hardy-Weinberg equation?
p + q = 1
p2 + 2pq + q2 = 1
