What can you say about the rate of silent mutation and non-synonymous mutations?
Silent mutations accumulate at a faster rate than non-synonymous mutations as they are hidden from selection
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Saturation of transversions occur sooner than transitions, T or F?
F- transitions occur more readily than transversions.
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What is an a) advantage b) disadvantage of recombination?
a) Breaks up linked genes/alleles so destroys beneficial gene combos, b) allows new genetic variation by gene shuffling and bringing together mutations from different sources.
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What is linkage disequilibrium?
When alleles from different genes are always inherited together
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How does recombination lead to gene duplication?
When chromosomes are wrongly aligned (mispaired) it leads to unequal crossing over so some genes will be duplicated
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What is duplication and how does it occur?
It occurs via unequal crossing over during recombination, transposition or non-segregation of chromosomes during cell division. It results in a section of chromosome or genes are duplicated. The duplicated region is free from selection pressure!
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What are polyploids? Which ones are infertile?
Organisms with extra chromosomes e.g. 2n, 3n...etc. Polyploids with an odd number of chromosomes are usually infertile.
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What are the 3 types of chromosome rearrangements?
Translocation, fission and inversion.
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What are the 2 types of changes resulting from DNA repair?
gene conversion, concerted evolution
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What is gene conversion?
When a mutation has occurred, proof reading enzymes will repair the mutation by copying the allele from the other homologous chromosome
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Is gene conversion always random?
No- repair can be biased towards one allele resulting in homogenisation of
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What is concerted evolution and how does it come about?
This is when different genes in a gene family evolve in concert so each gene locus comes to have the same genetic variant. It occurs through duplication then gene conversion
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What are the 3 mechanisms behind acquisition of new DNA?
Transposition, hybridisation, horizontal gene transfer
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What are transposable elements
'Parasitic DNA' that jumps from one location to the next, usually encoding their own transposase enzyme
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What are the 2 types of transposable elements?
Class 1: retrotransposons which copy and paste by RNA being reverse transcribed, leave a copy behind. In Class 2 there is no RNA intermediate and only some leave a copy behind
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What are the effects of transposable elements?
Can knock out genes by landing in the middle of them and disrupting function, can cause recombination by providing the necessary 'matches' when it otherwise wouldn't have occurred. Also inversions, deletions & translocations
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If on a phylogenetic tree there is a straight line from one genus to a completely unrelated genus, what can be inferred?
That horizontal gene transfer has occurred, probably due to a virogene
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How does horizontal gene transfer occur in bacteria? 2 mechanisms
transformation of exogenous DNA into the host cell in plasmid form which may also result in antibiotic immunity. Bacteriophage infection also results in gene transfer
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How does horizontal gene transfer actually occur from the cytoplasm to the nucleus?
Endosymbiotic bacteria integrate into cells and evolve into chloroplasts and mitochondria, there is then horizontal gene transfer from these organelles to the nucleus
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Which of the above changes doesn't occur in asexual organisms?
recombination and hybridization
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what is the selection type that keeps more than one variant in a pop?
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