Exam II - Chapter 6

Question 1

a situation in which allele and genotype frequencies in an ideal population do not change from one generation to the next

Answer 1

the hardy-weinberg equilibrium

Question 2

hardy-weinberg theorem relies on these 5 assumptions:

Answer 2

No selection
No mutation
No migration
No genetic drift (chance events)
When random mating occurs

Question 3

when alleles are not in equilibrium

Answer 3

evolution is occurring

Question 4

Hardy-weinberg is violated (evolution occurs) when

Answer 4

there is: selection

there are: mutations, migration, chance events, mates are not chosen at random

Question 5

serves as the fundamental null model of population genetics

Answer 5

hardy-weinberg theorem

Question 6

when all alternative alleles have disappeared

Answer 6

fixed allele

Question 7

when does fixation occur

Answer 7

when all individuals are genetically identical at a locus - happens in small populations

Question 8

differential reproductive success that happens for a reason

Answer 8

selection

Question 9

differential reproductive success that just happens; non-selection, random form of evolution; does not lead to adaptation

Answer 9

genetic drift

Question 10

change in frequencies of allele copies in populations resulting from sampling error in drawing error in drawing gametes from gene pool to make zygotes and from chance variation in the survival and/or reproductive success of individuals; resulting in non-adaptive evolution

Answer 10

genetic drift

Question 11

genetic drift results in a loss of heterozygosity- how is this for evolution?

Answer 11

heterozygosity –> good for evolution

homozygosity –> bad for evolution

Question 12

M&M example

Answer 12

sampling error

Question 13

(Graphs in book pg. 162 and quiz question) the smaller the population the _________ the genetic drift and the more variable the ______ frequency

Answer 13

stronger, more variable allele frequency (all over chart) where as a larger pop stays more steady

Question 14

example of population bottleneck

Answer 14

northern elephant seals

Question 15

events in which the number of individuals in a population is reduced drastically, even if the dip in numbers is temporary, it can have lasting effects on the genetic variation of a population

Answer 15

genetic bottleneck

Question 16

could be a big problem for bottlenecks that lack genetic diversity

Answer 16

disease - could wipe out entire species

Question 17

___ alleles are most likely to be lost during population bottle neck

Answer 17

rare (figure 6.9 page 164)

Question 18

a type of genetic drift describing the loss of allelic variation that accompanies founding of a new population from a very small number of individuals

Answer 18

founder effect

can cause the new population to differ considerable from the source population

Question 19

the success of an organism at surviving and reproducing and thus contributing offspring to future generations

Answer 19

fitness

Question 20

the success of the genotype at producing new individuals (its fitness) standardized by the success of other genotypes in the population

Answer 20

relative fitness (of a genotype)

Question 21

example of founder effect

Answer 21

silvereye birds: started in mainland Australia and then traveled from island to island and lastly ended in Norfolk island. the most diversity and genetic alleles on the mainland and the least on norfolk island (where they are most likely to go extinct

Question 22

selection that decreases the frequency of alleles within a population; occurs whenever the average excess for fitness of an allele is less than zero

Answer 22

negative selection

Question 23

selection that increases the frequency of alleles within a population; occurs whenever the average excess for fitness of an allele is greater than zero

Answer 23

positive selection

Question 24

the condition when a mutation in a single gene affect the expression of many different phenotypic traits

Answer 24

pleiotropy

Question 25

occurs when the effects of an allele at one genetic locus are modified by alleles at one or more other loci

Answer 25

epistasis

Question 26

alleles that yield twice the phenotypic effect when two copies are present

Answer 26

additive allele

Question 27

rare genotypes have higher fitness than common genotypes; this process can maintain genetic variation within populations

Answer 27

negative-frequency dependent selection

Question 28

*quiz question* a type of genetic drift describing the loss of allelic variation that accompanies formation of a new population

Answer 28

founder effect

Question 29

*quiz question* occurs when the effects of an allele at on locus are modified by alleles at one or more other loci

Answer 29

epistasis

Question 30

*quiz question* selection that favors more than one allele; it acts to maintain genetic diversity

Answer 30

balancing selection

Question 31

*quiz question* this is when rare genotypes have higher fitness than common genotypes; this process can maintain genetic variation in a population

Answer 31

negative frequency-dependant selection

Question 32

*quiz question* an allele that yields twice the phenotypic effect when 2 copies are present at a given locus than when only a single copy is present is known as an

Answer 32

additive allele

Question 33

example of negative frequency-dependent selection

Answer 33

elderflower orchid: some dark purple, some yellow; produce no nectar but trick bees- when bees land they take orchids pollen with them; risk-bees that visit orchids with no pollen (reward) can learn to avoid them

Question 34

what does it mean when elderflower orchids "leapfrog" color frequencies

Answer 34

when purple color is low and yellow high - bees learn to avoid yellow b/c no pollen and go to purple more often then purple become more predominant and the opposite happens. keeps going back and fourth *fitness is better when more rare color*

Question 35

selection that favors more than one allele; it acts to maintain genetic diversity in a population by keeping alleles at frequencies higher than would be expected by chance or mutation alone

Answer 35

balancing selection

Question 36

examples of balancing selection

Answer 36

negative frequency-dependant selection, heterozygous advantage

Question 37

what effect does natural selection have on deleterious mutations

Answer 37

it eliminates them

Question 38

fox and gray squirrel polymorphism example

Answer 38

color difference; wanted white squirrels so killed gray squirrels but this was bad because it was reducing genetic diversity and thus increasing the chance of extinction

Question 39

in the fox and gray squirrel example what was the big disadvantage of being white

Answer 39

many tumors found on white squirrels - UV damage

Question 40

describe differences of being heterozygous and homozygous when it comes to sickle cell anemia?

Answer 40

AA - homo dominant; susceptible to getting malaria AS - hetero - ADVANTAGE b/c you don't have health problems from sickle cell and you also have protection from malaria SS - homo recessive - health problems/lower fitness; suffer from sickle cell anemia

Question 41

the probability that the two alleles at any locus in an individual will be identical by descent

Answer 41

inbreeding coefficient (F)

Question 42

as inbreeding increases

Answer 42

survival decreases, deleterious genes increase

Question 43

a reduction in the average fitness of inbred individuals relative to that of outbred individuals; it arises because rare, recessive alleles become expressed in a homozygous state where they can detrimentally affect the performance of individuals

Answer 43

inbreeding depression

Question 44

what was the significance of the collard lizard example healthy vs actual populations and what were some ways to possibly fix it

Answer 44

healthy population should have many different genes, but it is found that separate populations have mostly only one or 2 genes each. could bring outside females in, remove barriers, mix lizards around to other populations to mix genes, etc.

Question 45

Genetic drift is non-selection, _____ form of evolution

Answer 45

Random

Question 46

_____ are more greatly influenced by genetic drift than _____ populations.

Answer 46

Small populations; large

Question 47

Genetic drift results in loss of

Answer 47

Heterozygosity

Question 48

Genetic drift does NOT lead to _____, selection does.

Answer 48

Adaptation

Question 49

A _____ population goes extinct more readily.

Answer 49

Small population

Question 50

_____ is higher with a smaller sample

Answer 50

Sampling error

Question 51

Genetic drift results from random _____

Answer 51

Sampling error

Question 52

In a small population, there is a higher chance all alleles _____, despite how common.

Answer 52

All alleles lost

Question 53

_____ will be more likely to occur on mainland

Answer 53

Evolution

Question 54

Population more likely to _____ on norfolk

Answer 54

Go extinct

Question 55

When a gene has a frequency higher than normal, that indicates

Answer 55

Sampling error (founder effect)

Question 56

Recessive will be slower to fix. Why?

Answer 56

Heterozygotes will not show phenotype and will take a while for homozygotes to appear. Once they do, seelction will quickly carry it to fixation

Question 57

Some forms of selection maintain diversity in populations. For example?

Answer 57

Negative frequency-dependent selection

Question 58

Drift more powerful in _____ population. Selection more powerful in _____ population.

Answer 58

Drift - small | Selection - large

Question 59

Inbreeding depression results in _____

Answer 59

Reduced fitness

Question 60

As F increases, survival _____ and deleterious genes _____

Answer 60

Survival decreases, deleterious genes increase