Deck 25: Quantitative Genetics and Multifactorial Traits

Question 1

Meristic traits are characterized by having phenotypes that are described by _____ .

A)irrational numbers
B)complex numbers
C)whole numbers
D)imaginary numbers
E)prime numbers

Answer 1

whole numbers

Question 2

What is the term given to a random subset of individuals who are selected for measurement in a particular study?

A)placebos
B)representatives
C)controls
D)sample

Answer 2

D

Question 3

Continuous inheritance is often related to the term quantitative inheritance.Why?

Answer 3

In continuous inheritance,we consider each involved locus as having a quantitative input on the production of a single characteristic of the phenotype.In addition,although it may not always be the case,we would consider each gene product to be qualitatively similar.

Question 4

In the early part of the twentieth century,Nilsson- Ehle and others described experiments showing that multiple loci may be involved in the inheritance of certain traits.Such patterns are often called _____ .

A)continuous traits
B)polygenic traits
C)indeterminate traits
D)threshold traits

Question 5

If the proportion of F₂ individuals resembling either of the two most extreme phenotypes the parental phenotypes)can be determined,what formula can be applied to determine the number of gene pairs involved?

A)1/4n where n is the number of gene pairs
B)
C)
D)2n + 1 where n is the number of gene pairs

Question 6

Assume that a cross is made between tall and dwarf tobacco plants.The F₁ generation showed intermediate height,while the F₂ generation showed a distribution of height ranging from tall to dwarf,like the original parents,and many heights between the extremes.These data are consistent with which one of the following modes of inheritance?

A)multiple- factor inheritance
B)codominance
C)alternation of generations
D)incomplete dominance
E)hemizygosity

Question 7

Polygenic traits often demonstrate a _____distribution when the phenotypes from a proper sample are represented in a histogram.

A)Poisson
B)normal
C)binomial
D)uniform

Question 8

Which of the following is not a statistical value often used to represent a sample when evaluating QTLs?

A)standard deviation
B)mean
C)mode
D)variance

Question 9

When a trait is polygenic,but has a small number of discrete classes,it is said to be an _____ trait.

A)oncogenic
B)threshold
C)meristic
D)continuous
E)qualitative

Question 10

Bell- shaped distributions produced by plotting results of F₂ and F₃ crosses are typical of which type of inheritance?

A)multiple- factor inheritance
B)codominance
C)alternation of generations
D)hemizygosity
E)incomplete dominance

Question 11

Given the following numbers,calculate the mean: 10,12,14,16,18.

A)18
B)13
C)10
D)14

Question 12

s² = S X_i - X ²/n - 1 is the formula for calculating which statistical value?

A)covariance
B)standard deviation
C)variance
D)mean

Question 13

Quantitative inheritance involves the interaction of a number of gene loci.The pattern of genetic transmission typical of quantitative inheritance is _____ .

A)typical of Mendelian inheritance
B)discontinuous distributions such as 3:1
C)continuous variation of phenotypic expression
D)usually a pattern that clearly reflects dominance and recessiveness
E)a 9:3:3:1 ratio

Question 14

Assume that in the F₂ of a series of crosses,1/64 of the offspring resemble one of the parents P .How many gene pairs are involved in producing these results?

A)16
B)3
C)32
D)6
E)64

Question 15

Assume that four polygenic gene pairs are involved in determining phenotypes of F₂.How many phenotypic classes are expected?

A)9
B)8
C)16
D)4

Question 16

Assume that you are studying a trait determined by a number of polygenes.If there are seven phenotypic categories,how many genes are probably involved?

A)4
B)2
C)7
D)3

Question 17

The 9:3:3:1 ratio is typical of a dihybrid cross in which complete dominance and independent assortment occur.What is the dihybrid ratio with independent assortment of polygenes?

Question 18

How many gene pairs are involved in generating a typical 1:4:6:4:1 ratio?

A)3
B)4
C)2
D)6

Question 19

When multiple genes contribute to the expression of a phenotype they are called _____ .

A)concordant alleles
B)homozygous alleles
C)heterozygous alleles
D)nonadditive alleles
E)additive alleles

Question 20

What formula can be used to determine the number of categories phenotypes possible in the F₂ results of a polygenic system?

A)s = where s is the number of gene pairs
B)1/4n where n is the number of gene pairs
C)2n + 1 where n is the number of gene pairs
D)

Question 21

Interpret the meaning of an H² broad- sense heritability value that approaches 1.0.

Question 22

What is meant by the term heritability? Describe the components of heritability and provide a brief explanation of each.Of what interest is heritability to animal and plant breeders?

Question 23

Which human trait would be expected to have high concordance?

A)weight
B)eye color
C)contracting measles
D)hair length

Question 24

Define the term broad- sense heritability H².What is implied by a relatively high value of H²? Express aspects of broad- sense heritability in equation form.

Question 25

Which of the following is not a component of phenotypic variance?

A)the interaction between genetics and environment
B)environmental variance
C)the covariance
D)genetic variance

Question 26

Interpret the meaning of an H² broad- sense heritability value that approaches 0.0.

Question 27

What is the formal expression used to examine the relative importance of genetic versus environmental factors?

A)narrow- sense heritability index h² = V_A/V_P
B)broad- sense heritability index H² = V_G/V_P
C)correlation coefficient s = _s2
D)genotype- by- environment interaction variance VP = VG + VE + VG*E

Question 28

Which statistical value is used to represent the linkage of the increase in one measurement to the increase in a second measurement?

A)covariance
B)correlation coefficient
C)standard deviation
D)variance

Question 29

We often refer to the host of genetic factors in the genome that have an influence on a particular gene's expression as its genetic background.What influence does genetic background have over the phenotype of the organism?

Question 30

As used in twin studies in mammals,distinguish between the terms concordant and discordant.

Question 31

Which value of narrow- sense heritability h² indicates a selection will have a significant impact in altering the initial population?

A)20
B)0.20
C)0.99
D)99

Question 32

Individuals with the same genetic background and a high degree of homozygosity are said to be isogenic.Of what value are isogenic strains in genetic studies?

Question 33

Which statement best describes h² narrow- sense heritability ?

A)The deviation from additive components when they behave epistatically.
B)The proportion of phenotypic variance due to additive genotypic variance alone.
C)It measures the contribution genotypic variance to total phenotypic variance.
D)The genotypic variance due to additive action of various QTLs.

Question 34

Identical twins are___ .

A)homozygotic
B)dizygotic
C)monozygotic
D)hemizygotic

Question 35

Provide a brief definition of the term interactive variance.

Question 36

Which of the following mammalian traits exhibits a relatively low h² value?

A)birth weight in cattle
B)tail length in mice
C)litter size in mice
D)milk yield in cattle

Question 37

To estimate how much the means of a variety of like samples drawn from the same population might vary,what statistic is often used?

A)standard deviation of the mean
B)variance of the mean
C)standard error of the mean
D)relative error of the mean

Question 38

Describe the value of using twins in the study of questions relating to the relative impact of heredity versus environment.

Question 39

If one is attempting to determine the influence of genes or the environment on phenotypic variation,inbred strains with individuals of a relatively homogeneous or constant genetic background are often used.Variation observed between different inbred strains reared in a constant or homogeneous environment would likely be caused by genetic factors.What would be the source of variation observed among members of the same inbred strain reared under various environmental conditions?

Question 40

What is the name of the process of selecting a specific group of organisms from an initially heterogeneous population for future breeding purposes?

A)artificial selection
B)diversity selection
C)natural selection
D)exclusive selection

Question 41

Polygenes are involved in determining___ .

A)traits that have a distinct all or none phenotype
B)traits that are strictly determined by environmental factors
C)continuously varying traits
D)traits that are strictly determined by genetic variance

Question 42

A "marker" in a genetic sense usually represents a site along a chromosome where a specific nucleotide sequence exists.What specific phrase is used when such markers are identified by restriction endonucleases and a particular set of DNA fragments is generated?

A)restriction site
B)expression QTL
C)RFLP
D)QTL

Question 43

In the analysis of quantitative traits,positions on chromosomes called quantitative trait loci QTLs are often discussed.In the same context,restriction fragment length polymorphisms RFLPs are also discussed.What is the relationship between QTLs and RFLPs?

Question 44

Concordance refers to the frequency with which members of a twin pair express a___ trait.

A)unrelated
B)mutated
C)similar
D)different

Question 45

What are QTLs?

Question 46

Heritability is a measure of the degree to which the phenotypic variation of a given trait is due to ___.

A)somatic mutations
B)epigenetic regulation
C)environmental factors
D)genetic factors

Question 47

How would the use of a large series of monozygotic and dizygotic twins enhance studies on the genetic basis of human behavior?

Question 48

Expression QTL mapping allows researchers to characterize___ .

A)loci that modify the rate of protein translation
B)loci that control gene expression
C)loci that have high mutating rates
D)loci that encode phenotypes

Question 49

Typically,one thinks of identical MZ twins being genetically identical.However,genomic differences do exist between MZ twins by epigenetic processes.What are epigenetic processes?

Question 50

___alleles are those that are not epistatic over nonallelic genes that influence the same phenotypic characteristic.

A)Additive
B)Threshold
C)Nonadditive
D)Discontinuous

Question 51

Which trait is probably not caused primarily by genes that behave codominantly or epistatically?

A)height
B)general body structure
C)skin color
D)eye color

Question 52

Which theory suggests that many factors or genes contribute to the phenotype in a cumulative or quantitative manner?

A)threshold gene theory
B)heritability theory
C)additive gene theory
D)multiple factor hypothesis