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BIOL 1102 Exam Two
Feb 9 - Evolution of Genes and Genomes
| Question | Answer |
|---|---|
| What is a point mutation? | if a point mutation goes to fixation in a population, it is substitution |
| What does substitution tell us? | pattern can tell us about the nature of selection on that gene |
| What is a synonymous/silent substitution? | substitution that DOES NOT CHANGE the amino acid that is specified, no fitness effect |
| How is the fate of the mutant allele of a silent substitution determined? | governed mainly by drift |
| What is a nonsynonymous substitution? | substitution that does cause a change in the amino acid specified |
| How is the fate of the mutant allele of a nonsynonymous substitution determined? | mutation IS assumed to have a fitness effect, governed mainly by selection, depending on whether the change is advantageous or deleterious |
| When is rate of N/S = 1? | an amino acid replacement is neutral with respect to fitness, a change that has no effect on survival or reproduction |
| When is rate of N/S > 1? | amino acid position is under POSITIVE SELECTION for change, more mutation that changed the amino acid occured -> spread throughout the population -> stayed in the lineage that are present than synonymous ones |
| When is rate of N/S < 1? | amino acid position is under PURIFYING SELECTION, rate of synonymous substitutions is higher than nonsynonymous, |
| What are two assumptions in genetic analysis when comparing synonymous substitution and nonsynonymous subtitution? | assume that all nucleotide positions mutations at equal frequencies, there has been time for evolutionary forces to act on these sequences after the mutations arose |
| What is the molecular clock hypothesis? | DNA and protein sequences evolve at a relatively constant rate over time and among different organisms |
| How does the molecule clock work? | uses the average rate at which a given gene or protein accumulates changes to gauge the time of divergence for a particular split in a phylogeny |
| What things can be used to calibrate a molecule clock? | fossil record, known times of divergence, or biogeographic dates (ex. time of separations of continents) |
| What does the slope represent of proportion of amino acid differences vs. time | average rate of change represents the molecular clock in amino acid sequences |
| How do genomes grow and acquire new genes? | by duplications some or all of the existing genes in the genome, or by acquiring genes from other species |
| What are four types of duplicating gene mechanisms? | polyploidy, gene duplication, de Novo genes, transposable elements |
| How do species acquire genes from other species? | lateral/horizontal gene transfer |
| Where can gene duplications arise from? | errors in recombination or replication |
| What are the four fates of gene duplication? | nonfunctionalization, neofunctionalization, subfunctionalization, no functional divergence |
| What is nonfunctioanlization? | copy becomes nonfunctional due to mutations (psuedogene) |
| What is neofunctionalization? | copy accumulates substitutions that allow it to perform a new function |
| What is subfunctionalization? | functionality of the original gene is distributed among the two copies |
| What happens in no functional divergence/genetic robustness | both copies retain their original function |
| What is de novo gene formation? | new genes from non-coding DNA |
| How does de novo gene formation occur? | genes can evolve from non-coding portions of DNA by gaining transcription and codons, in either order |
| What are pseudogenes? | genes that are no longer functional, all mutations in these genes are neutral NOT deleterious or beneficial |
| What is horizontal gene transfer? | movement of genetic material between organisms that are nor related by parent and offspring |
| What are the four types of HGT? | transformation, conjugation, transduction, endosymbiosis |
| What is transformation? | bacteria takes up DNA from their environment |
| What is conjugation? | bacteria directly transfers genes to another cell |
| What is transduction? | bacteriophages (bacterial viruses) move genes from one cell to another |
| What is endosymbiosis? | one organism at first lives inside another, endosymbiont loses function in some of its genes and becomes reliant on the host organism (mitochondria/chloroplatss) |
Created by:
goldengalleon