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Evolution > Exam 1 Lecs - 6 > Flashcards

Exam 1 Lecs - 6 Flashcards

1
Q

in an extremely large population, if heterozygotes have a higher population, this will keep the two alleles in … at …. indefinitely

A

equilibrium;

maximum frequency

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2
Q

in a finite generation, even if heterozygote has higher fitness, there is a chance that one allele will be …
Drift vs. selection depends on … and …

A

fixed;
size of population;
strength of selection

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3
Q

scientists set up 24 populations and selected b+ and b individuals such that the frequency of both alleles would be …

  • 12 populations with 50 males and 50 females and another 12 with 5 males and 5 females
  • maintained populations for … generations, selecting individuals … to make up the new generations
  • examined 240 individuals of offspring to calculate the …
A

0.5;
20;
randomly;
frequency of the alleles

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4
Q

Scientists set up 24 populations and selected b+ and b individuals such that the frequency of both alleles would be 0.5:
- outcome: Tendency of … frequency of allele b+ in population of 100–> … occurring bc the frequency of the allele is …

A

increasing;
natural selection;
increasing

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5
Q

Scientists set up 24 populations and selected b+ and b individuals such that the frequency of both alleles would be 0.5:
- outcome:
with population of 10, still have the tendency to increase in frequency, but there’s more … in changing in frequency from one population to the other. Some cases of …/… of the allele. In some cases, even with selection favoring the allele, it was …

A

variation;
fixation; loss;
still lost

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6
Q

If all the genotypes start with the same fitness, there’s …, just ….

A

no selection;

drift

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7
Q

neutral theory of molecular evolution:
- one of the most influential theories after the …
- 3 kinds of mutations:
… - tend to be eliminated by natural selection
…. - rises and falls in frequency as a result of genetic drift, no … on it

A

modern synthesis;
deleterious;
neutral mutation;
selection

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8
Q

neutral theory of molecular evolution:
- 3 kinds of mutation:
beneficial - could still be lost to drift depending on …, since it will start with a … But, otherwise, it tends to … via … –> Again, still dependent on population size and strength of selection

A

population size;
low frequency;
rise; fixation; natural selection;

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9
Q

neutral theory of molecular evolution:

  • scientists started sequencing proteins in the 60s to get the number of changes between same type of protein in different organisms - compare … via … among organisms
  • can calculate rate of change in … in protein over time
A

number; differences;

aa

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10
Q

neutral theory of molecular evolution:
scientists started sequencing proteins in the 60s to get the number of changes between same type of protein in diff organisms:
- can calculate rate of change in aa in protein over time. the formula is: …/…./…

A

of differences/length of aa sequence/(total time that the two species diverged*number of species - typically 2)

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11
Q

neutral theory of molecular evolution:

  • … relationship between aa differences and time
  • more aa differences with … time period between divergence
A

linear;

longer

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12
Q

neutral theory of molecular evolution:

linear relationship between aa differences and time:

  • suggests … mutation model - mutations happen every certain period of time
  • no … fixing mutations
A

clocklike;

natural selection

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13
Q

neutral theory of molecular evolution:

linear relationship between aa differences and time:
- Kimura proposed that most mutations that we see in aa sequences are … and are only influenced by … bc the ones that are deleterious are … from the population and if they’re beneficial they should drive allele frequency to …

A

neutral;
drift;
quickly removed;
fixation

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14
Q

neutral theory of molecular evolution:

- … is the mechanism responsible for most molecular evolution, not …

A

genetic drift;

natural selection

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15
Q

every time there’s a beneficial mutation that protein will … and also carry with it the other … within that sequence - rare event

A

increase in frequency;

neutral mutations

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16
Q

if most mutations are neutral we expect to find more mutations in … position of codons bc this tends to lead to … mutations that don’t change the protein

A

third;

synonymous

17
Q

controversy about neutral theory:

  • bc its a bold claim - suggests that natural selection is … at the molecular level
  • can test if selection is occurring in a fragment of a sequence - take rate of … and rate of … substitutions per site
A

rare;
nonsynonymous;
synonymous

18
Q

controversy about neutral theory:

  • can test if selection is occurring in a fragment of a sequence:
  • take number of nonsynonymous and rate of synonymous subs per rate:
  • dN/dS … - deleterious
  • dN/dS … - neutral
  • dN/dS … - advantageous
A

<1;
= 1;
> 1

19
Q

controversy about neutral theory:
dN/dS > 1 - advantageous —> this would be evidence … neutral theory bc you’re finding a gene where number of nonsynonymous mutations is … than synonymous ones, which only … could explain

A

against;
much larger;
selection

20
Q

controversy about neutral theory:

- Hughes and nei tested neutral theory by estimating ratio of … to … substitutions in genes vital to immune function

A

replacement (nonsyn);

silent (synonymous)

21
Q

controversy about neutral theory:
Hughes and Nei research:
- when mammalian cells are infected by pathogen, they display a piece of that pathogen in their membrane. Immune cells kill the infected cell then - … enables this to occur. This is a cluster of genes encoding … that display pathogen proteins

A

MHC;

membrane proteins

22
Q

controversy about neutral theory:
Hughes and Nei research:
- Found that in MHC loci between humans and mice, there were more … sites than … site changes

A

replacement;

silent

23
Q

controversy about neutral theory:
Hughes and Nei research:
- found that in MHC loci between humans and mice, there were more replacement sites than silent site changes. This could only happen in the replacement changes were … - … causes replacement changes to spread through the population more quickly than neutral alleles can spread by … (i.e. …)

A

advantageous;
positive selection;
chance;
drift

24
Q

controversy about neutral theory:
- another study focused on … gene, which is associated with apoptosis in neural development –> found that some nonsyn/syn ratios were … but for human and chimp comparison, it was … - suggests that … was driving the increase in frequency here

A

BRCA1;
lower than 1;
higher than 1;
selection

25
Q

in some genes there is … Not all mutations are …, some are …

A

selection;
neutral;
beneficial

26
Q

Neutral theory explains three main concepts:

  • … evolution of nucleotide sequences
  • why … subs outnumber … subs in most genes
  • acts as a … that allows research to identify examples of positive selection on nucleotide sequences
A

clock like;
silent;
replacement;
null hypothesis

27
Q

Bc there are some …, development of modified version of neutral theory –> … theory

A

non-neutral mutations;

nearly neutral theory

28
Q

nearly neutral theory:

  • nearly neutral mutations change the fitness …
  • if population is small, mutations … in frequency due to …
A

just a tiny bit;
fluctuate;
drift

29
Q

nearly neutral theory:
- if population is really large, … can then act to change frequency of those alleles and even if change in fitness is minor, with enough generations … can still act on it and …

A

natural selection;
selection;
change frequencies

30
Q

nearly neutral theory:

- for a nearly neutral mutation, relative power of drift and selection depends on …

A

population size

31
Q

nearly neutral theory:

- this theory brings back … as a variable to the neutral theory

A

population size

32
Q

nearly neutral theory:

- nearly neutral mutations behave as … mutations in small populations and their fate is determined by …

A

neutral;

drift

33
Q

nearly neutral theory:

- nearly neutral mutations behave as … mutations in large populations and their fate is determined by …

A

non-neutral;

selection

Evolution (27 decks)

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