Deck 5: Complex Patterns of Inheritance

Question 1

Twins are said to be concordant for a trait when

A) both twins exhibit the trait.
B) only identical twins exhibit the trait.
C) only fraternal twins exhibit the trait.
D) fraternal twins more often show the trait than identical twins.
E) None of these is true.

Answer 1

A

Question 2

A heritability value of 0.6 for IQ indicates that 60 percent of a person's IQ results from genetic influence.

Answer 2

False

Question 3

The additive model for polygenic inheritance proposes that the genes controlling a trait are all on one chromosome.

Answer 3

False

Question 4

Clubfoot and cleft palate are traits

A) that are congenital birth defects.
B) that have discontinuous distribution.
C) that are multifactorial.
D) whose distribution can best be explained by the threshold model.
E) that have all of these characteristics.

Question 5

Which statement about the interaction between genes and environment is most correct?

A) Phenotypic variation is derived from a single source.
B) The phenotype, once determined, is invariable.
C) The phenotype is produced by interaction of genotype and the environment.
D) The phenotype can be quantified into genotypic and environmental components.
E) None of these is true.

Question 6

A diet rich in ___ has been shown to reduce the incidence of spina bifida.

A) vitamin C
B) niacin
C) folate
D) vitamin D
E) vitamin E

Question 7

If a trait has a heritability of 0.5, this means that

A) all variation in the population is caused by genotypic differences.
B) all variation in the population is caused by environmental differences.
C) the variation in the population is the result of epigenetic effects.
D) the genotype and environment contribute equally to the variation seen in the population.
E) None of these is true.

Question 8

Sickle cell disease exhibits a variety of symptoms and is more severe under stressful situations. Sickle cell disease is an example of a _____ genetic disorder.

A) discontinuous
B) continuous
C) polygenic
D) multifactorial
E) phenotypic

Question 9

King Frederick William of Prussia failed in his attempts to create an army of giants because of all the following reasons except one. Select the exception.

A) Human life spans are too long.
B) Children of the crosses were actually shorter than their parents.
C) Size in humans is too complex a trait.
D) There was too much resistance to his program because of ethical considerations.
E) There are no exceptions. All of these reasons are correct.

Question 10

The multifactorial threshold model is helpful in genetic counseling to predict recurrence risks.

Question 11

Mendel's experiments with pea plants yielded useful results because

A) pea plants exhibit continuous variation.
B) pea plants exhibit a variety of inheritance patterns.
C) pea plants show discontinuous variation and complete dominance.
D) pea plants are sterile.
E) more than one of these are correct.

Question 12

Which of the following is not a characteristic of continuous variation?

A) Traits can be quantified by measurement.
B) Only a single gene pair contributes to the phenotype.
C) The effect of each additive allele is small.
D) Phenotypes show wide variation in expression.
E) All of these are characteristics of continuous variation.

Question 13

Many studies have been conducted on the heritability of obesity. With fairly strong consistency they indicate that the heritability of this trait is about:

A) 0.1
B) 0.3
C) 0.5
D) 0.7
E) 0.9

Question 14

For threshold traits the liability for a genetic disorder is distributed among individuals in a normal curve.

Question 15

The heritability of a trait can be defined as

A) the sum of all phenotypic variation in the population
B) the average amount of genetic variation in each individual
C) the proportion of variability in a population that is caused by genetic variance
D) the absolute measurement of genotypic variation in a population
E) the proportion of variability caused by the environment

Question 16

Most evidence indicates that skin color is controlled by how many gene pairs?

A) One
B) Two to three
C) Three to four
D) Five to seven
E) More than twelve

Question 17

According to the threshold model, for a family in which a disorder occurs, the risk of the disorder decreases as relatedness decreases.

Question 18

The tall and short phenotypes in pea plants are examples of

A) polygenic traits.
B) continuous traits.
C) multifactorial traits.
D) discontinuous traits.
E) gene interaction.

Question 19

The role of nutrition in the improvement of spina bifida is an example of a _____ effect.

A) cumulative
B) polygenic
C) epigenetic
D) penetrative
E) phenotypic

Question 20

In a certain population with a mean IQ of 100, the heritability of IQ was measured at 0.6. A chapter of Mensa in this population has an average IQ of 140. If they are otherwise typical of their population, about how many of their IQ points can be attributed to their genes?

A) 60
B) 84
C) 24
D) 100
E) 40

Question 21

How have twins been useful in studies of multifactorial traits?

Question 22

Scientists are now using an expanded definition of intelligence, beyond IQ, called ____________________.

Question 23

Name five human traits that could be described as multifactorial from twin studies and concordance rates.

Question 24

The correlation coefficient for totally unrelated people is ____________________.

Question 25

DZ twins are no more or less genetically similar to each other than ____________________ are.

Question 26

All multifactorial traits are polygenic but the reverse is not true.

Question 27

Phrenology and craniometry are no longer considered valid methods of studying intelligence.

Question 28

Davenport and Davenport estimated that two genes control skin color in humans, while, according to others, as many as four different genes are involved. Why has there been so much difficulty in determining the number of genes controlling this trait?

Question 29

The heritability of IQ is about 0.5. This is interpreted by some to mean that IQ is 50 percent genetic and 50 percent environmental. Is this correct? What exactly does a heritability value of 0.5 mean?

Question 30

If a trait is genetically determined, the correlation between DZ twins should be lower than that for MZ twins.

Question 31

The hormone leptin is produced in ____________________ cells.

Question 32

______________ twins result from a single fertilization event.

Question 33

Give two different genotypes for individuals with intermediate skin color and show the different types of gametes that they could produce.

Question 34

______________ traits are those that result from the interaction of genes and the environment..

Question 35

Concordance values for twins are only useful in studying traits that are completely heritable.

Question 36

Discuss the factors responsible for regression to the mean.

Question 37

How would you go about determining whether a trait was controlled by a single gene or by polygenes? Would pedigree analysis be of use in answering this question?

Question 38

The type of breeding experiments done by King Frederick William of Prussia would not be possible today given available technologies.

Question 39

Provide evidence from a specific example that argues for a substantial role for the environment in determining IQ.

Question 40

While monozygotic twins share the same genome, their fingerprints are not identical. Why is this so?

Question 41

Using a large poster board, construct a Punnet Square involving three genes for skin color. One of the parents is completely dominant for all three genes and the other parent is completely recessive for all three genes. Then construct a graph of the number of offspring (y-axis) versus phenotype (skin color from lightest to darkest on the x-axis).