Genome evolution- 2 Flashcards
why is genome revolution relevant to evolution?
- shows what evolution i s expected to do
- helps to interpret evolutionary patterns
at what regions do X and Y chromosomes recombine?
pseudo autosomal regions
synonymous change?
base change that does not alter protein sequence
codon bias usage?
preferential use of certain synonymous codons by tRNA
single gene change significant example?
Single gene in yeast leads to cooperation against threats
gene also helps to detect cheaters
why do synonymous changes accumulate at a faster rate than non syn?
why does flip flopping eventually occur of syn changes?
- less likely to be selected against
- because only a finite amount of changes available so eventually they plateau
what evidence is there that chromosome fusions have occurred in primates?
human chromosomes hybridise to gibbons?
example of chromosome inversion?
what happens to the genes?
seaweed fly
they become locked together because no recombination within inversion?
what is a pseudogene?
a non functional copy of a gene produce by a duplication event
example of duplication of genes?
in spiders silk genes
large scale duplication event?
African toad genome is tetraploid due to duplication event
How do DNA changes occur?
- external factors
- error during replication
- recombination
- biased direction of repair
- horizontal gene transfer: plasmid. transposable elements. virogene. endosymbiont bacteria
- hybridisation
what are the classes of transposable elements (selfish genetic elements)?
- class 1: retrotransposable elements: require RNA intermediate and reverse transcription
- class 2: DNA transposons dont require RNA intermediate
evolution of transposable elements have shown they have?
repeatedly inserted themselves into moths
effect of transposable elements on DNA?
- knock out genes
- inversions
- deletions
why is the mutation rate slow?
- because of proofreading enzymes and repair
- those that are transmitted are selected against in the new gen
evolution over a short period is called what? and characterised by?
- ecological
- alterations in allele frequency (level of heterozygosity )rather than the generation of new alleles
adaptation was shown to be constrained by mutation rate i which experiment?
evolution of E.coli- only 3 molecule ways?
example of small step change resulting in evolution?
1 base change in 3 different positions of the gene for lactose tolerance
example of dynamic evolution?
snake venom going from toxic to non venomous
example of coevolution of genomes?
squid and bioluminescent bacteria
(western clawed frog study) what do comparative genomics tell us about mammalian genome evolution compared to amphibians?
- shows that there is an intact region within human chrom 1 identical to that in the frog: intact for 350 million years
- DNA added to the intact region + an intact region in the frog been split in humans: more frequent fusion and fission of chromosomes in mammals
(genome readies itself paper) why do the toxin genes in cone snails have lots of genetic variation between species?
- particular sequences influence the ease at which enzymes can do their repair job
- some dna more prone to copying error (repeated sequences for example)
this leads to malleable exon with a tendency to mutate therefore genetic variation
