Deck 9: Evolution at Multiple Loci: Quantitative Genetics

Question 1

In cases where selection consistently favors a higher (or lower)value of a trait or phenotype,the result over time is a change in the average value of a trait in the population.This mode of selection is known as ________.

A) directional selection
B) stabilizing selection
C) disruptive selection
D) selection gradient

Answer 1

A

Question 2

When Bradshaw and colleagues investigated the quantitative trait loci (QTL)of two species of Mimulus (Mimulus cardinalis and Mimulus lewisii),they used marker loci as a way to map the QTLs.Their results are shown in the accompanying figure.According to these results,________.

A) the differences in genotype for the majority of these QTLs explained small amounts of the variations in flower phenotypes for both species
B) some of the QTLs did have pronounced effects on the flowers' phenotypes
C) at least one QTL explained 90% of the phenotypic variance for each species
D) All of the above.

Answer 2

D

Question 3

The fraction known as the broad-sense heritability (where VG = genetic variation,VP = phenotypic variation,and VE = environmental variation)is expressed by ________.

A) VG/VP
B) VG/VG + VE
C) VG/VP + VE
D) VG/VE
E) A and B are both accurate.

Answer 3

E

Question 4

Determining the slope of the best-fit line for a data set of midparent versus midoffspring values by utilizing least-squares linear regression generates an estimate of heritability known as the ________.

A) phenotypic variation
B) environmental variation
C) broad-sense heritability
D) narrow-sense heritability

Question 5

The abbreviation QTL stands for ________,[three words] which are those genes that influence nonqualitative traits.

Question 6

The authors of your textbook described two ways in which the strength of selection can be measured.What are these two ways?

Question 7

Heritability measures ________.

A) the difference between the environmental and genetic influences on a heritable trait of an individual
B) the degree of influence that the sum of the environmental and genetic factors have on a trait
C) the portion of the total variation in a trait that is due to variation in genes
D) the distribution of the phenotypes of the individuals in a normally distributed population

Question 8

Continuously variable traits typically have a(n)________,[two words] otherwise known as a "bell-curve."

Question 9

Traits that are conditioned by one locus are most appropriately termed ________.

A) qualitative traits
B) quantitative traits
C) continuously variable traits
D) environmentally conditioned traits

Question 10

The total variation in a trait is known as the ________.

A) phenotypic variation
B) genetic variation
C) environmental variation
D) broad-sense heritability
E) narrow-sense heritability

Question 11

Multiple trait analysis (beak width and beak depth)on the medium ground finch,in response to the drought of 1976-77,has generated the three-dimensional graph,shown in the accompanying figure.If the blue triangles represent fitness levels for the quantified parameters,then the birds showing the greatest fitness should have ________.

A) deep, wide beaks
B) deep, narrow beaks
C) shallow, wide beaks
D) shallow, narrow beaks

Question 12

________ refers to the fraction of the total variation in a trait that is due to variation in genes.

Question 13

Determining the best-fit line for a data set by utilizing the least-squares linear regression,the slope of the resulting line represents a useful estimate known as the ________,[two words] for which we use the symbol h².

Question 14

When Clausen and colleagues grew genetically identical individuals of the yarrow plant at different elevations,the results are shown in the accompanying figure.This observation verifies that ________.

A) yarrow plants mutate quickly when grown in different environments
B) the genotypes of yarrow plants has nothing to do with how tall these plants grow
C) yarrow plants grow taller at lower elevations and shorter at higher elevations regardless of their genotype
D) the genotypes of yarrow plants interacts with environmental influences to produce the phenotype

Question 15

The experimental work of Edward East in 1916,shown in the accompanying figure,confirmed that ________.

A) qualitative traits are essentially impossible to characterize because of their complex nature
B) quantitative traits are essentially impossible to characterize because of their complex nature
C) quantitative traits are established by the combined influence of Mendelian alleles at multiple loci
D) quantitative traits return to qualitative attributes when allowed to outcross in the wild

Question 16

Variation among individuals that is due to variation in factors other than environmental influences is called ________.

A) phenotypic variation
B) genetic variation
C) broad-sense heritability
D) narrow-sense heritability

Question 17

Traits that are conditioned by multiple loci and form continuously variable phenotypes that are conditioned by both the genotypes and environmental influences are most appropriately termed ________.

A) qualitative traits
B) quantitative traits
C) discrete categorical traits
D) Mendelian traits

Question 18

Data on survival of juvenile black-bellied seedcrackers as a function of beak size is shown in the accompanying figure.Given the relative survival rates of juvenile birds in terms of both the lower mandible width and length,this is a clear example of ________.

A) directional selection
B) stabilizing selection
C) disruptive selection
D) selection gradient

Question 19

To learn the location of and determine the role that QTLs have on phenotypes,researchers look for associations between a marker locus genotype and phenotype.Examples of research focusing on such methods have been conducted on ________.

A) human personality traits
B) human diseases such as Crohn's disease
C) the speed of thoroughbred race horses
D) All of the above.

Question 20

Variation among individuals that is due to factors other than genetic factors is called ________.

A) phenotypic variation
B) environmental variation
C) broad-sense heritability
D) narrow-sense heritability

Question 21

Estimating heritability using twin studies has been useful for certain human phenotypes,such as general cognitive abilities.Explain the logic behind this,and how such studies are performed.

Question 22

Some have proposed that where human IQ scores are concerned,heritability can tell us something about the causes of differences between population means such as ethnic groups.Explain why this perspective is erroneous.

Question 23

Three distinct modes of selection have been proposed and studied in natural populations.Each mode is different in its effects on the mean value and distribution of phenotypes.Compare and contrast each of these three modes.

Question 24

Suppose we consider the figures below.If Figure A represents a measurable trait in a population at time 0,and Figure B represents the same trait some generations later,we can conclude that the type of selection called ________ selection has been at work.


Figure A Figure B

Question 25

In populations where individuals with intermediate values of a trait have the highest fitness,the average value of the trait does not change over time,but the variation tends to be reduced.This set of circumstances is known as ________.[two words]

Question 26

________ selection and ________ selection tend to reduce the amount of variation in a population,whereas ________ selection tends to increase the amount of variation in a population.

Question 27

It becomes possible to predict evolutionary changes in a population after we have measured two attributes affecting the population in question.What two measures allow us to make such predictions?

Question 28

Compare and contrast qualitative traits/genetics with quantitative traits/genetics.

Question 29

Explain,using examples/equations,the similarities and differences between broad-sense and narrow-sense heritability estimates.

Question 30

In populations where individuals with extreme values of a trait have the highest fitness,the average value of the trait may not change,but the amount of variance in the trait does increase over time.This set of circumstances is known as ________.[two words]