Exam 2

Look at graph first if needed: Effective population size: the number of individuals in the population that contribute alleles to the next generation (simplified definition) • Four remaining sites in Wisconsin - Johnson et al. 2004 • Do you expect the Mead population in Wisconsin to experience genetic drift more like an ideal population of (A) 200 individuals or (B) 20 individuals?

B.) because there is only 19 individuals that are reproducing so that is basically the same as 20. Their experiencing genetic drift as 20.

Genetic Drift: If a neutral allele has the frequency of 0.20 in a population and we're only consider the effects of genetic drift, then the probability that it will_____. A. reach fixation is 20/2=10% if the organism is diploid B. be lost is 2*20=40% if the organism is diploid C. be lost is 20/2=10% if the organism is haploid D. reach fixation is 20% E. be lost is 20%

D

Allele?

Different forms of a gene since they work in pairs.

describe the relationship between agouti, mcle and pigmentation in mice:

Evolution in Oldfield Mice • Results: show associations between genetic regions and the phenotypes • High LOD score = stretch of DNA associated with differences in phenotype • Low LOD score = stretch of DNA not (or just a little) associated w/diff in phen. • Agouti & Mc1r are known to be associated with pigmentation • Mc1r is a receptor, activity is linked to pigment production • Agouti can repress Mc1r activity

True (A) or false (B)? This probability is also influenced by whether the allele was previously at a high or low frequency.

False:

A phenotype is an observable/measurable feature of an organism. True (A) or false (B)? Phenotype refers only to morphological or behavioral traits.

False: physiological, cellular and biochemical traits are also considered.

locus

Location of a gene on a chromosome

genetic polymorphism

The existence of two or more distinct alleles at a given locus in a population's gene pool.

Projections of increasing seasonal color mismatch of snowshoe hares?

The ones properly matches have lower mortality rates.

True (A) or false (B)? Soon after the island of Hawaii rose above the sea surface (about half a million years ago), the evolution of life on this new island would have been strongly influenced by the founder effect.

True

Assumption: only genetic drift, no other evolutionary mechanism True (A) or false (B) or no idea (C)? an allele with the frequency of 78% has a 78% chance of being fixed in this population.

True.

True (A) or false (B)? If you created a mouse with increased agouti expression, then this mouse will likely have a lighter coat color than a mouse with normal agouti expression.

True.

True (A) or false (B)? Suppose there was strong selection on the phenotype encoded by alleles of a particular gene in generation X. If their offspring (generation X+1) mates randomly and no evolutionary mechanisms are affecting the population, then the genotype frequencies of generation X+2 will be in Hardy-Weinberg equilibrium.

True. The point in this exercise is to show that if all the criterion of HW are met, this can happen for more than one generation.

3. Cases when genetic drift is especially strong: True (A) or false (B)? A genetic bottleneck and the founder effect both describe special cases of genetic drift that involve small population sizes but the founder effect is different in that the original population splits into two, in separate geographic locations.

True: -red: bottle neck: population greatly diminishes. -green: moves to new location.

Assumption: only genetic drift, no other evolutionary mechanism True (A) or false (B) or no idea (C)? N=population size. 2If an allele has just arisen by mutation, and is represented by only one among the (2N) alleles at this locus in the population, its frequency = 1/(2N). The fact that N is part of this equation, shows that an initially rare allele is more likely to be fixed in a small than a large population.

True: 1/(2N), Just by doing the math, it is obvies that as the population increases, the lower the chance of it being fixed.

The Grants' study (Science, 2006) is evidence for character displacement in Darwin's finches because they ____. A. directly observed a change in beak size in the opposite direction from what was expected based on food availability alone B. quantified beak depth in multiple populations of G. fortis and G. magnirostris and populations in sympatry were consistently more different than in allopatry C. collected long-term data that allowed them to demonstrate what happens in the absence and presence of a competitor in the same population D. All of the above

a

phenotype? provide an example.

a physical manifestation of a person's genes. Ex: Hot girl with blond hair blue eyes, or red hair and green eyes.

True (A) or false (B)? If Ne /N = 0.50, then then we expect a given allele to be lost or gone to fixation faster than if Ne /N = 0.10. (You can assume that N is the same in both equations.)

a.) False

ideal population?

all individuals reproduce.

In which of these environments do you predict the Ester1 allele frequency to be the highest? A. High predation by other arthropods; high levels of organophosphate insecticide B. Low predation by other arthropods; high levels of organophosphate insecticide C. Low predation by other arthropods; low levels of organophosphate insecticide

b.

Heritability estimates the proportion of ________. A. genetic variation in a population that can be attributed to the phenotype B. phenotypic variation in an individual that can be attributed to variation among genes C. phenotypic variation in a population that can be attributed to variation among genes D. none of the above

c

Which of these populations do you expect to change (evolve) most in response to selection? Assume strength of selection is identical in the different populations. look at the graph: A. The human population B. The tree swallow population C. The wild radish population D. A and B E. None will evolve; evolution by natural selection requires h2 of at least 90%.

c

look at the graph: Which trait values do you predict for each species in sympatry? A. Same B. Sp. 1 higher, Sp. 2 lower trait value C. Sp 1 lower, Sp 2 higher trait value D. B or C could apply E. Don't know

c

look at the graph: Below you see graphs that depict the change in frequency of a neutral allele in four populations that differ in size. Which graph reflects the smallest population size?

d<c<a<b -smallest: d-some are driven to fixation and other ones are lost really quickly. -largest: b-very little change because of high population.

remember of the bird example and the founder effect: What do you predict happens to allelic diversity in each subsequent population?

decreases

Hardy-Weinberg Principle: • Assumptions There are three assumptions. True (A) or false (B)?

false its actually 5: 1-No gene flow (no migration) 2-No mutation. 3-No natural selection 4-Random Mating 5-No genetic drift

a surprising change in birds. describe it:

first drought the beak size got bigger. -in principle, the second drought it should have gone up again, but it did not. this is because a knew bird in town arived, G. magnirostris which has a same beak size as Geospiza fortis, and now they competed for the bigger foods so the small beak birds g. fortis were able to thrive more due to the lack of competition thus beak size size decreasing on average.

If Noah took only pairs of individuals of each species...which evolutionary mechanism would have caused the greatest problem in future generations?

genetic drift. is an extreme example of the founder effect.

Hardy-Weinberg Principle: Null hypothesis

if no evolutionary mechanisms are operating (& random mating), then genotype frequencies should be in H-W equilibrium.

What is the maximum number of different alleles that can theoretically be present in a population of 114 diploid individuals?

look in the video

what is a good indicator of genetic drift? why only for neutral loci?

low neutral loci. -if the organism is homozygus, is easier for it to be slected. Ex: if rat is white, it can blend in with the sand. If rat is brown it can mix in with the woods, but i it is neutral, it wont fit in iether. Is like being luke warm in the Jesus metaphor.

Can heritability have a negative value?

no

Allelic diversity: ?

number of alleles present in the population at a particular locus.

look at the graph: do the math on a separate sheet of paper without looking at the answers: 1-which genotype experiences the most negative purifying selection? 2-which allele will likely go to fixation?

oct. 15: 1:05:25

what does p and q represent in Hardy Weinberg?

p=frequency of dominant allele. q=frequency of recessive allele. -

gene

- encodes protein(s)

Allele

- variant of a particular gene - a diploid cell has two alleles of a given gene - a haploid cell has one allele of a given gene- variant of a particular gene - a diploid cell has two alleles of a given gene - a haploid cell has one allele of a given gene

gene?

section of DNA that codes for phenotype.

Heterozygosity:

the fraction of individuals in a population that are heterozygous for a particular locus.

how is frequency calculated in hardy Weinberg?

the number of the allele (weather is dominant or recessive), divided by the grand total of all alleles.

True (A) or false (B)? A high LOD score indicated an association between different alleles at one locus and phenotypic variation.

true

two rodent species are consistently more different from each other when they occupy the same habitat than when they live separately: true or false: this pattern is consistent with character displacement but does not conclusively demonstrate that the underlying process is character displacement.

true

Suppose you are looking at discrete phenotypic variation: some green swordtails, X. helleri, have spots and other do not. Can you tell, just based on this information, whether variation in this trait has a genetic basis?

-No, I cant tell. the phenotypic variation could be due to genetic and or environmental factors.

Suppose you have a group of females that you're giving minimum food, just enough to keep them alive. They can reproduce but have few resources. True (A) or false (B)? Her offspring will have small horns.

true.

Genotype? provide an example.

type of genes: An organism's genetic makeup, or allele combinations. Ex: carrier of cystic fibrosis.

selection coefficient:

watch a video on youtube if you dont get it. oct, 15. 41:25 1. calculate relative fitness. 2. selection coefficient. 3.

do the math problem in a separate sheet of paper without looking at the answer: what is the relative fitness of the genotypes below?

watch video if you want: oct, 15. 37:54

look at graph:

without looking at the answer:

Character displacement? is this disruptive selection?

yes it is disruptive selection.

look at the graph: Genetic Drift in Drosophila • Peter Buri's work in the 1950s • 107 replicate lab populations of fruit flies • 19 generations total • 16 flies/population for 18 generations • Randomly sampled 8 males, 8 females to start the next generation True (A) or false (B)? 1. The histogram bars represent number of populations with a particular bw-75 allele frequency. 2. This experiment highlighted the strong effects of genetic drift but natural selection also played a key role.

1-True 2-False: Peter Buri tried his best to exclude natural selection.

Label the following statements/phrases as best describing A. allele(s), B. gene(s), C. chromosome(s), D. locus/loci, E. genotype(s) 1. _____ are alternative forms of a stretch of DNA that encodes proteins. 2. The ____ is the place on a chromosome where a particular stretch of DNA is found. 3. In a diploid individual, two copies of the same gene constitute the____.

1.) Alleles 2.) Locus 3.) Genotype

This exercise assumes random mating among surviving adults in an infinitely large population. w11 = the fitness of the A1A1 genotype, w12 = the fitness of the A1A2 genotype and w22 = the fitness of the A2A2 genotype. You find that A1A1 individuals produce on average 24 offspring, while A1A2 , individuals produce on average 20 offspring, and the A2A2 individuals produce on average 22 offspring each generation. 1.) True (A) or false (B)? This is an example of heterozygote advantage (also called heterosis). Or C = no idea 2.) What is the relative fitness of the A1A1 genotype? w11 = What is the relative fitness of the A1A2 genotype? w12 = What is the relative fitness of the A2A2 genotype? w22 = Enter the first decimal place of the fitness of the A2A2 genotype (e.g. 5 if it's 0.53) 3.) What do you predict is going to happen to the allele frequencies? A. A1 will be lost and A2 will be fixed B. A1 will be fixed and A2 will be lost C. Both A1 and A2 alleles are maintained in the population at intermediate frequencies. D. Either A1 or A2 will be fixed; which will depends on their initial allele frequencie

1.) B 2.) picture. 3.) C Watch video if confused: oct, 15, 18:48

look at the graph: E. coli LTEE: relative fitness over time: True (A) or false (B)? The relative fitness of E. coli in a new environment (limited glucose in flask solution) increased rapidly in the first several thousand generations. It continued to increase throughout the experiment but at a slower rate.

A

does it matter for rate of fixation (through natural selection) weather an allele is dominant, recessive or additive? a-yes b-no

A; oct, 15. 1;10

gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time. Ex: take all the alleles pairs and separate them and shuffle them in a bag.

what is Fitness?

• Success of an organism in surviving and reproducing and thus contributing offspring to the next generation • Population genetics thinking (specific genes, alleles, genotypes) • Fitness is relative: individuals with certain genotype leave more offspring relative to individuals with other genotypes • Relative fitness of genotype with the highest fitness is set to w = 1, all other genotypes in the population have a relative fitness between 0 and 1