Exam 1 Lecs - 6 Flashcards
in an extremely large population, if heterozygotes have a higher population, this will keep the two alleles in … at …. indefinitely
equilibrium;
maximum frequency
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 …
fixed;
size of population;
strength of selection
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 …
0.5;
20;
randomly;
frequency of the alleles
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 …
increasing;
natural selection;
increasing
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 …
variation;
fixation; loss;
still lost
If all the genotypes start with the same fitness, there’s …, just ….
no selection;
drift
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
modern synthesis;
deleterious;
neutral mutation;
selection
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
population size;
low frequency;
rise; fixation; natural selection;
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
number; differences;
aa
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: …/…./…
of differences/length of aa sequence/(total time that the two species diverged*number of species - typically 2)
neutral theory of molecular evolution:
- … relationship between aa differences and time
- more aa differences with … time period between divergence
linear;
longer
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
clocklike;
natural selection
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 …
neutral;
drift;
quickly removed;
fixation
neutral theory of molecular evolution:
- … is the mechanism responsible for most molecular evolution, not …
genetic drift;
natural selection
every time there’s a beneficial mutation that protein will … and also carry with it the other … within that sequence - rare event
increase in frequency;
neutral mutations
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
third;
synonymous
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
rare;
nonsynonymous;
synonymous
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
<1;
= 1;
> 1
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
against;
much larger;
selection
controversy about neutral theory:
- Hughes and nei tested neutral theory by estimating ratio of … to … substitutions in genes vital to immune function
replacement (nonsyn);
silent (synonymous)
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
MHC;
membrane proteins
controversy about neutral theory:
Hughes and Nei research:
- Found that in MHC loci between humans and mice, there were more … sites than … site changes
replacement;
silent
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. …)
advantageous;
positive selection;
chance;
drift
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
BRCA1;
lower than 1;
higher than 1;
selection
in some genes there is … Not all mutations are …, some are …
selection;
neutral;
beneficial
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
Bc there are some …, development of modified version of neutral theory –> … theory
non-neutral mutations;
nearly neutral theory
nearly neutral theory:
- nearly neutral mutations change the fitness …
- if population is small, mutations … in frequency due to …
just a tiny bit;
fluctuate;
drift
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
nearly neutral theory:
- for a nearly neutral mutation, relative power of drift and selection depends on …
population size
nearly neutral theory:
- this theory brings back … as a variable to the neutral theory
population size
nearly neutral theory:
- nearly neutral mutations behave as … mutations in small populations and their fate is determined by …
neutral;
drift
nearly neutral theory:
- nearly neutral mutations behave as … mutations in large populations and their fate is determined by …
non-neutral;
selection
