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Genetics > Chapter 23 - Quantitative Genetics > Flashcards

Chapter 23 - Quantitative Genetics Flashcards

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1
Q

Two classes of traits that do NOT show continuous variation are meristic traits, which do not have an infinite range of phenotypes, and threshold traits, which have a small number of discrete phenotypic classes.

  • True
  • False
A

True

Meristic traits and threshold traits are two classes of polygenic traits that do not show continuous variation.

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2
Q

Which of the following is an example of a meristic trait?

  • Weight
  • Number of bristles on a fruit fly
  • Oil content in corn kernels
  • Height
A

Number of bristles on a fruit fly

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3
Q

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

  • Usually a pattern that clearly reflects dominance and recessiveness
  • Discontinuous distributions such as 3:1
  • A 9:3:3:1 ratio
  • Typical of Mendelian inheritance
  • Continuous variation of phenotypic expression
A

Continuous variation of phenotypic expression

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4
Q

Environmental factors typically influence inheritance of…

  • Polygenic traits
  • Codominance
  • Dominantly inherited traits
  • Trihybrid crosses
  • Multiple alleles
A

Polygenic traits

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5
Q

When a trait is polygenic, but distinguished from continuous and meristic traits by having a small number of discrete classes, it is said to be a ______ trait.

A

Threshold

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6
Q

Polygenes are involved in determining continuously varying or multiple-factor traits.

  • True
  • False
A

True

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7
Q

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

A

9 phenotypic classes

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8
Q

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

3 gene pairs

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9
Q

Two samples with identical means do not necessarily have the same standard deviation.

  • True
  • False
A

True

(One sample may have either greater or lesser variation than another sample, even though the means of the two samples are the same.)

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10
Q

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

  • Codominance
  • Hemizygosity
  • Incomplete dominance
  • Alternation of generations
  • Multiple-factor inheritance
A

Multiple-factor inheritance

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11
Q

Characteristics exhibited by continuously varying traits include…

  • A 9:3:3:1 ratio
  • 3:1 and 1:1 ratios
  • Quantification by measuring, weighing, counting, etc
  • Sex-linked genes only
  • Autosomal genes only
A

Quantification by measuring, weighing, counting, etc.

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12
Q

Which term is defined as “a measure of the variation in a phenotype (for a polygenic trait in a given population) due to genetic “factors”?

  • Variance
  • Narrow-sense heritability
  • Broad-sense heritability
  • Response
A

Broad-sense heritability.

Broad sense heritability is expressed as the ratio of the total genetic variance to the phenotypic variance, Vg:Vp

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13
Q

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

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14
Q

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

  • True
  • False
A

True

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15
Q

Traits such as height, general body structure, skin color, and some behavioral traits are probably caused primarily by genes that behave codominantly or epistatically.

  • True
  • False
A

False

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16
Q

Which of the following statements about twin and twin studies is FALSE?

  • Twin studies have been used to try to determine the role of heredity versus environment
  • Fraternal twins are as close genetically to each other as are monozygotic twins
  • If the concordance values for monozygotic twins are much higher than for dizygotic twins, the trait probably has a strong genetic basis
  • Dizygotic twins are an important control for any study using monozygotic twins
A

Fraternal twins are as close genetically to each other as are monozygotic twins

(This statement is false. Fraternal twins arise from two sperm fertilizing two eggs and are no more genetically similar than any two other siblings. Monozygotic twins have identical genetic compositions.)

17
Q

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

  • True
  • False
A

False

18
Q

What is the difference between an eQTL and a pQTL?

  • An eQTL phenotype is the amount of protein produced; a pQTL phenotype is the amount of RNA produced
  • The term eQTL refers to twins that both express a given trait; the term pQTL refers to twins where only one twin expresses the trait
  • A pQTL phenotype of the amount of protein produced; an eQTL phenotype is the amount of RNA produced
  • An eQTL is a proportion of an F2 population carrying the dominant phenotype, and a pQTL is the proportion containing the recessive phenotype
A

A pQTL phenotype of the amount of protein produced; an eQTL phenotype is the amount of RNA produced

19
Q

What is the difference between continuous and discontinuous variation?

  • In discontinuous variation the influences of each gene pair are not additive and more typical Mendelian ratios. In continuous variation, different gene pairs interact (usually additively) to produce a phenotype that is less “stepwise” in distribution.
  • In continuous variation the influences of each gene pair are not additive and more typical Mendelian ratios. In discontinuous variation, different gene pairs interact (usually additively) to produce a phenotype that is less “stepwise” in distribution.
A

In discontinuous variation the influences of each gene pair are not additive and more typical Mendelian ratios. In continuous variation, different gene pairs interact (usually additively) to produce a phenotype that is less “stepwise” in distribution.

20
Q

Which of the two is most likely to be the result of polygenic inheritance?

  • Inheritance involving polygenic systems follows a more continuous distribution
  • Inheritance involving polygenic systems follows a more discontinuous distribution
A

Inheritance involving polygenic systems follows a more continuous distribution.

Genetics (4 decks)

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