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Genomics (GEN501) > Molecular Evolution > Flashcards

Molecular Evolution Flashcards

1
Q

What is ‘on the origin of species’ about?

A

→ Theory to explain the current variety of life on earth

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2
Q

What are the two main concepts in ‘the origin of species’?

A

→ Natural selection and fitness

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3
Q

What is the definition of natural selection?

A

→ The effects of a wide range of factors on the frequency of heritable changes in a species

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4
Q

What is the definition of fitness?

A

→ How well a species is able to reproduce in its environment

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5
Q

What is the relationship between fitness ad selection?

A

→ Anything that increases fitness is selected for

→ anything that decreases fitness is selected against

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6
Q

What happens to neutral changes?

A

→ They vary randomly

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7
Q

What is modern synthesis?

A

→ unifying evolution with genetics to explain the molecular processes underlying evolution

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8
Q

What is the main source of heritable variation in a species

A

→ Genetic variation

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9
Q

What 4 things are the frequency of genetic variants affected by?

A

→ Selection
→ Mutation
→ Migration
→ Genetic drift

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10
Q

What types of genetic variants are selected for?

A

→ variants that confer a positive advantage

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11
Q

What is an example of a positive advantage?

A

→ resistance to disease
→ an ability to metabolise a new food source
→ change in appearance to enhance mate choice

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12
Q

What parts of the genomes are resistant to change and why?

A

→ They are conserved

→ because they contain vital sequences

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13
Q

What is mutation?

A

→ process by which variation arises

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14
Q

What does genomic variant frequency depend on?

A

→ Selection

→ When the variants first occurred

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15
Q

What are the three possibilities of low frequency in a rare variant?

A

→ May have arisen recently
→ be deleterious and being selected against
→ both

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16
Q

What is migration and what does this result in genetically and what is this called?

A

→ Physical movement from a different population
→ Result in new pools of variants being introduced to an existing population
→ Admixture

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17
Q

Why does admixture need to be taken into account when studying populations?

A

→ Population frequencies of specific variants can change purely due to admixture and not be disease related

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18
Q

What is genetic drift?

A

→ How the frequency of a variant changes in a population due to chance

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19
Q

What are 2 reasons that variation is not passed on?

A

→ Not all organisms will pass on their genetic variants

→ mechanisms such as recombination will also result in not all variants being passed on

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20
Q

What are all variants subject to?

A

→ Genetic drift

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21
Q

What types of sequences don’t show variation?

A

→ DNA sequences that is vital to the survival of an organism

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22
Q

What happens if variants occur in conserved regions?

A

→ They will be selected against as they are likely to have a strong deleterious effect

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23
Q

Why is there some flexibility in variation in conserved regions?

A

→ there is flexibility in the third base of codons as some amino acids are encoded by multiple codons

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24
Q

Where is high conservation seen and what is the exception?

A

→ Coding regions

→ but not in exons as they have non coding regions

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25
Q

Where is intermediate conservation seen?

A 
→ promoter
→ 5' UTR
→ Splicing sites
→ 3' UTR 
→ Terminator
26
Q

Where is low conservation seen?

A

→ Introns
→ 3rd base of codons
→ Terminator (vague signals such as GC rich regions)

27
Q

What can be used to generate an evolutionary profile and why?

A

→ Cross species comparison

→ To see how genes change over time

28
Q

What is phylogenetics?

A

→ Working out the history of the genome

29
Q

What is needed for phylogenetic sequencing?

A

→ Observe sequences

→see how are they related

30
Q

What does a phylogenetic tree show?

A

→ Illustrate relatedness of different species

31
Q

What does distance show on a phylogenetic tree?

A

→ The more distance the less related they are

→ distance is related to both evolutionary pressures and time

32
Q

How is time estimated on phylogenetic trees?

A

→ measuring mutation rates

33
Q

What is the theory behind the introduction of HIV to the human population?

A

→ a contaminated polio vaccine

→ some polio vaccines were produced with cultured chimpanzee cells which could have been infected with SIV

34
Q

What is gene duplication?

A

→ Duplication of a DNA sequence containing a gene

35
Q

What is the typical mechanism of gene duplication?

A

→ Unequal crossing over

36
Q

What are the two options after duplication?

A

→ One copy can continue the original function

→ the other copy can evolve new functions by changes in the coding or control sequences

37
Q

What is unequal crossing over?

A

→ Recombination between sequences that are not the correct sequence but are very similar
→ often low copy number repeat sequences

38
Q

When does unequal crossing over usually happen?

A

→ often low copy number repeat sequences

39
Q

How many clusters of the globin gene are there?

A

→ 2

40
Q

Where are the alpha like globin genes?

A

→ chromosome 16
→ 4 genes
→ 3 pseudogenes

41
Q

Where are the beta like globin genes?

A

→ chromosomes 11

→ 5 genes and one pseudo gene

42
Q

How are the globin genes arranged?

A

→ In order of expression during development

43
Q

What are the 3 types of Hb?

A

→ Embryonic
→ Fetal
→ Postnatal

44
Q

What is the control region of the beta globin cluster?

A

→ beta LCR

45
Q

How have globin genes evolved?

A

→ Divergence

46
Q

What are pseudogenes?

A

→ non functioning genes

47
Q

What allows the expression of globin genes at different stages?

A

→ Divergence of promoters has occurred so they bind different transcription factors and allow expression of genes at different stages of development

48
Q

What is fetal Hb made from?

A

→ Alpha and gamma subunits

49
Q

What is adult Hb made from?

A

→ Alpha and beta subunits

50
Q

How are pseudogenes formed?

A

→ After gene duplication one gene maintains original function and the other diverges

51
Q

What do pseudogenes contain?

A

→ many mutations and are non functional

52
Q

When do sickle cell symptoms start and why?

A

→ 5- 6 months

→ change between HbF and HbA

53
Q

What are the symptoms of sickle cell?

A

→ Anaemia
→ Acute pain episodes - crises - due to oxygen deprivation
→ Increased infection
→ stroke, hypertension

54
Q

What are the symptoms due to?

A

→ Sickling of red blood cells

55
Q

How does sickle cell occur?

A

→ A single base change in the beta globin gene of HbA

56
Q

What is the codon change in sickle cell?

A

→ GAG to GTG

→ Glutamine to valine at position 7

57
Q

What kind of a disease is sickle cell?

A

→ Autosomal recessive

58
Q

What is the chance of a child getting SCD if the parents have 1 copy each?

A

→ 1 in 4

59
Q

What is the distribution of HbS?

A

→ Africa
→ Middle east
→ India

60
Q

Why has sickle cell not been selected against?

A

→ with one copy of HbS it improves reproductive fitness

→ because it confers resistance to severe malaria

61
Q

What does heterozygote advantage mean for HbS?

A

→ The variant is maintained because of the huge selection pressure

Genomics (GEN501) (19 decks)

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