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2B - Genetics & Evolution > week 7 > Flashcards

week 7 Flashcards

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Biology 101 flashcards
1
Q

What is SNP?

A

Single nucleotide polymorphisms (SNPs)
- SNPs arise by point mutation during DNA synthesis

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2
Q

What are INDELs

A

insertions and deletions.

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3
Q

What are CNVs

A

copy number variants:
- alleles in CNV differ in number of replicates
- some regions have 2 copies rather than 1

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4
Q

What are large structural variants?

A

when an INDEL is longer than 1000 bases it is considered large structural variants

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5
Q

What are the 2 methods of describing genetic variation?

A
  • pi
  • allele frequencies
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6
Q

How to measure diversity using pi

A

number of nucleotide differences between pairwise sequences / (no. go sequence comparisons x no. of sites)

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7
Q

How to measure diversity using allele frequencies?

A

number of A alleles / total number of alleles - hardy weignburgh

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8
Q

What are the expected genotype frequencies in the Hardy-Weinberg equilibrium model?

A

Homozygous AA: p²
Homozygous TT: q²
Heterozygous AT: 2pq

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9
Q

What are the assumptions of the model

A

Sexual, diploid, non-overlapping generations.
Random mating population.

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10
Q

What are the 3 modes of non-random mating?

A

assortative mating
disassortative mating
inbreeding

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10
Q

What is assortative mating vs disassortative mating

A
  1. more homozygous individuals
  2. more heterozygous individuals
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11
Q

What does inbreeding lead to?

A

more homozygous individuals, leads to more genetic diseases

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12
Q

What is the equation to find inbreeding coefficient?

A

1 - (Hoberved/2pq)
Hobserveed = observed frequency of heterozygotes
2pq = expected frequency of heterozygote

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13
Q

What does smaller populations lead to?

A
  • more genetic drift
  • lead to fixation (loss of alleles )
  • divergence between populations
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14
Q

What are the 3 types of selection and explain each

A
  1. directional selection
  2. disruptive selection
  3. stabilising selection
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15
Q

When a mutation is introduced, the frequency proportional to population of diploid is ___ of haploid

A

half

16
Q

Which mode of selections more costly? By how much?

A

sexual, 2 fold cost of sex because each time asexual reproduces it doubles but in sexual it takes 2 to make one

17
Q

Sex doesn’t require sexes, what does require sexes?

A

sexual selection

18
Q

What is sexual selection?

A

Sexual selection: a sub-set of natural selection used to describe the processes underlying the evolution of differences in attributes of males and females

19
Q

Why is sexual selection dealt differently to natural selection?

A

It is not the environment (or “Nature”) selecting, but other individuals of the same species for mating success

Rather than selection acting on ‘fitness’ characteristics, it acts on traits that give individuals a mating advantage

20
Q

Describe the common traits of female vs male gametes

A

male = many small and cheap
female = few, large and costly

21
Q

How can sexual selection arise in terms of parental investment

A

when parental investment is unequal, there can be sexual selection

22
Q

What is intra-sexual selection?

A

More competitive individuals (usually males) have increased fitness

Physical traits:
- Size
- Weaponry
- Sperm production
- Behaviour

23
Q

What is pre-copulation intra-sexual selection

A

A form of sexual selection that occurs before mating, involving competition among members of the same sex (typically males) to gain access to mates.

24
Q

What is Post-copulation intra-sexual selection

A

Intra-sexual selection can continue after mating, via:

  • Sperm competition
  • Mate guarding
  • Mate manipulation
  • Infanticide!
25
Q

What is selected on in in intersexual selection

A
  • epigamic characters
    • behaviour
    • ornamentation
  • chosen individuals (usually males) have increased fitness
26
Q

Why does mate choice happen?

A
  • Direct Benefits
  • Individuals are chosen because they provide direct benefits e.g. food, protection, parental care, etc.…
  • Male offers a female a nuptial prey gift, some offers themseles
27
Q

What is honest signalling?

A

individuals are chosen because their phenotype signals indirect tangible benefits (e.g. beneficial genes)

28
Q

What is the fisher’s runaway sexual selection model?

A
  1. mutations causing male traits that confer greater fitness to exaggerate more
  2. female mutation causes them to prefer those traits and mate
  3. produce ‘sexy sons’ (daughters prefer that trait)
29
Q

How does the fisher’s runaway sexual selection operate?

A

no longer needs a diet fitness benefits and is self perpetuating

30
Q

Give an example of sensory bias?

A

Tungara frogs have a sensory system that limits the sounds they can hear. Male calls that are successful operate at a frequency range that females can hear. Preference is arbitrary other than linkage to sensory system.

31
Q

What are the 2 indirect benefits

A

honest signalling or ‘sexy sons’ through runaway process.

32
Q

flatworm are hermaphrodites = capable of performing both reproductive functions
- wooclap: what role are the 2 flatworms fighting to carry out?

A

male because sperm is cheap to produce so they are fighting to be the male (less investment of energy)

33
Q
  • mormon cricket produce spermatophore (jelly capsule containing nutrient and sperm)
  • during courtship, male produced spermatophore and comes in contact in such a way where the nutrient is consumed by the female
  • Wooclap: what sex would you expect to compete for mates and which to be choosy?
A

in poor conditions: females to compete and males to be choosy. when conditions are poor and nutrients are limited, the thing that limits the female’s ability to maximise reproduction is their ability to get resource.

in good conditions: roles become reversed. the spermatophore becomes less meaningful to reproductive budget for female and males. males compete women are choosy

34
Q

if big testes lead to big success, why are there small testis males?

A

sexual selection is weaker than natural selection so cannot affect minimum size. there are physiological limits, so small testes males will eventually get a chance. ones with large testes go around mating during breeding season and eventually run out but those with small dont reed as virgouously so during late season they can mate with leftover females.

35
Q

example side-blotched lizards

  • 1st morph: orange thruts (large individualas), defends territory to ensure exclusive female access
  • 2nd morph: blue thurt (smaller), they find individual females and forms very close connection. exclusive to one female
  • 3rd morph: smallest with yellow thrut : females are also yellow so this morph sneaks in and mates in territory
A
  • frequency dependant selection = how the fitness changes depending on frequency of the morph.
  • six year cycle of rock paper scissors, when blue is dominant, yellow will beat them and they will be beat by orange
36
Q

why dont all individuals have attractive traits?

A
  • associated cost of having attractive traits
  • a trait favoured by sexual selection could not fit in viability selection

2B - Genetics & Evolution (9 decks)

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