Variation - 5

Question 1

What are the 3 general models for evolution

Answer 1

1. classical model
2. balance/selectionist model
3. neutral model

Question 2

Define classical model of evolution

Answer 2

mutations can be good or bad, but it doesn’t matter because there are not many of them
believed there were low levels of polymorphism

Question 3

Define balance/selectionist model

Answer 3

believed there is lots of polymorphism and that most individuals were heterozygous or had some sort of variation or mutation.
believed speciation wasn’t rare because of the abundance of variation. The variation allowed for natural selection to occur

Question 4

Define neutral model in evolution

Answer 4

believed that most mutations are deleterious, but natural selection rapidly removes them which results in most of the mutations being neutral. Suggests that mutations don’t make a significant impact on variation
variation is due to random chance.

Question 5

What model is most strongly accepted

Answer 5

balance/selectionist model

Question 6

What are the 2 types of summary statistics to determine how much variation occurs

Answer 6

1. haplotype diversity
2. allelic diversity (% polymorphic sites or heterozygosity)

Question 7

Define haplotype diversity

Answer 7

measure of how many haplotypes there are in a population and how common they are

Question 8

Define % polymorphic sites

Answer 8

multiple alleles at a single locus

Question 9

What are the two ways heterozygosity can be measured to determine variation

Answer 9

1. the frequency of heterozygotes
2. the fraction of genes that are heterozygous

Question 10

What determines phenotype

Answer 10

1. genotype
2. environment (phenotypic plasticity, usually cause range ex. flowers could be red to pink)
3. maternal effects (ex. red flower if parents two years old, pink if mother is four years old)
4. genomic imprinting (depends on if gets gene from mother or father on how its expressed)

Question 11

Can phenotype be used to determine genotype

Answer 11

No, because phenotype may not be on a single gene or the phenotype may not be heritable

Question 12

Instead of using phenotype to determine genotype, what can be used

Answer 12

DNA, because it is a powerful tool to get down to the base layer

Question 13

What creates variation (4)

Answer 13

mutation, recombination, gene flow, and hybridization

Question 14

What does the dn/ds ratio tell us evolution at a locus is due to

Answer 14

dn = nonsynonymous (phenotype change), ds = synonymous (no phenotype change)
dn/ds = 1 (drift)
dn/ds<1 -negative/purifying (nonsynonymous are deleterious, so selection gets rid of mutation)
dn/ds>1 - positive/diversifying (means more AA changes than neutral, generally means mutation has benefit)