Genome evolution- 2

Question 1

why is genome revolution relevant to evolution?

Answer 1

• shows what evolution i s expected to do

- helps to interpret evolutionary patterns

Question 2

at what regions do X and Y chromosomes recombine?

Answer 2

pseudo autosomal regions

Question 3

synonymous change?

Answer 3

base change that does not alter protein sequence

Question 4

codon bias usage?

Answer 4

preferential use of certain synonymous codons by tRNA

Question 5

single gene change significant example?

Answer 5

Single gene in yeast leads to cooperation against threats

gene also helps to detect cheaters

Question 6

why do synonymous changes accumulate at a faster rate than non syn?
why does flip flopping eventually occur of syn changes?

Answer 6

• less likely to be selected against

- because only a finite amount of changes available so eventually they plateau

Question 7

what evidence is there that chromosome fusions have occurred in primates?

Answer 7

human chromosomes hybridise to gibbons?

Question 8

example of chromosome inversion?

what happens to the genes?

Answer 8

seaweed fly

they become locked together because no recombination within inversion?

Question 9

what is a pseudogene?

Answer 9

a non functional copy of a gene produce by a duplication event

Question 10

example of duplication of genes?

Answer 10

in spiders silk genes

Question 11

large scale duplication event?

Answer 11

African toad genome is tetraploid due to duplication event

Question 12

How do DNA changes occur?

Answer 12

• external factors
• error during replication
• recombination
• biased direction of repair
• horizontal gene transfer: plasmid. transposable elements. virogene. endosymbiont bacteria
• hybridisation

Question 13

what are the classes of transposable elements (selfish genetic elements)?

Answer 13

• class 1: retrotransposable elements: require RNA intermediate and reverse transcription
• class 2: DNA transposons dont require RNA intermediate

Question 14

evolution of transposable elements have shown they have?

Answer 14

repeatedly inserted themselves into moths

Question 15

effect of transposable elements on DNA?

Answer 15

• knock out genes
• inversions
• deletions

Question 16

why is the mutation rate slow?

Answer 16

• because of proofreading enzymes and repair

- those that are transmitted are selected against in the new gen

Question 17

evolution over a short period is called what? and characterised by?

Answer 17

• ecological

- alterations in allele frequency (level of heterozygosity )rather than the generation of new alleles

Question 18

adaptation was shown to be constrained by mutation rate i which experiment?

Answer 18

evolution of E.coli- only 3 molecule ways?

Question 19

example of small step change resulting in evolution?

Answer 19

1 base change in 3 different positions of the gene for lactose tolerance

Question 20

example of dynamic evolution?

Answer 20

snake venom going from toxic to non venomous

Question 21

example of coevolution of genomes?

Answer 21

squid and bioluminescent bacteria

Question 22

(western clawed frog study) what do comparative genomics tell us about mammalian genome evolution compared to amphibians?

Answer 22

• 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

Question 23

(genome readies itself paper) why do the toxin genes in cone snails have lots of genetic variation between species?

Answer 23

• 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