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
in some genes there is ... Not all mutations are ..., some are ...
selection; neutral; beneficial
26
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
clock like; silent; replacement; null hypothesis
27
Bc there are some ..., development of modified version of neutral theory --> ... theory
non-neutral mutations; | nearly neutral theory
28
nearly neutral theory: - nearly neutral mutations change the fitness ... - if population is small, mutations ... in frequency due to ...
just a tiny bit; fluctuate; drift
29
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 ...
natural selection; selection; change frequencies
30
nearly neutral theory: | - for a nearly neutral mutation, relative power of drift and selection depends on ...
population size
31
nearly neutral theory: | - this theory brings back ... as a variable to the neutral theory
population size
32
nearly neutral theory: | - nearly neutral mutations behave as ... mutations in small populations and their fate is determined by ...
neutral; | drift
33
nearly neutral theory: | - nearly neutral mutations behave as ... mutations in large populations and their fate is determined by ...
non-neutral; | selection