Deck 18: Genetics of Behavior

Question 1

How are association studies different from the typical studies, which attempt to link a DNA marker to a trait?

A) Different types of DNA markers are employed.
B) More DNA markers are analyzed simultaneously.
C) Unrelated individuals are studied rather than families.
D) Much larger family groups over more generations are studied.
E) A broader description of the trait is employed.

Answer 1

C

Question 2

MZ twin concordance values are less than 100 percent in both bipolar disorder and schizophrenia. This suggests that these disorders are ______________.

A) strictly polygenic
B) multifactorial
C) X-linked
D) genetically dominant
E) not genetically based

Answer 2

B

Question 3

The genes that influence alcoholism are ______________.

A) alcohol dehydrogenase genes
B) aldehyde dehydrogenase genes
C) MAOA genes
D) a combination of two of these genes
E) unknown.

Answer 3

E

Question 4

Several types of evidence have linked bipolar disorder to genes. Which one of the following is NOT one of these types of evidence?

A) Biochemical studies
B) Twin studies
C) Adoption studies
D) Association studies
E) Studies involving degrees of relatedness

Question 5

What transgenic animal, other than mice, has been used to model human neurodegenerative diseases?

A) monkeys
B) Drosophila
C) rats
D) roundworms
E) frogs

Question 6

What is the function of a normal MAOA protein?

A) It breaks down neurotransmitters.
B) It carries neurotransmitters across synapses.
C) It is a neurotransmitter.
D) It is an enzyme essential in the formation of certain neurotransmitters.
E) It is an enzyme responsible for the construction of neurotransmitter receptors.

Question 7

Most single gene defects that affect human behavior do so

A) as a primary effect of the gene.
B) through their action on the structure, development, or function of the nervous system.
C) by affecting muscle metabolism.
D) by having only subtle effects on the nervous system.
E) by gene action that takes place only in the adult stage of life.

Question 8

Which of the following conditions is best described by a polygenic model?

A) Huntington disease
B) Lesch-Nyhan syndrome
C) Schizophrenia
D) Fragile-X syndrome
E) More than one of these

Question 9

The phenotype in many human behavioral traits are

A) due to minor genes with no single gene having a major effect.
B) due solely to environment.
C) due to environmental interaction and several genes.
D) due to minor genes with no single gene having a major effect and due to environmental interaction and several genes only.
E) due solely to environment and due to environmental interaction and several genes only.

Question 10

Since sons adopted by alcoholic men show a rate of alcoholism more like that of their biological father, there is an argument for the role of genetic factors in this disease.

Question 11

The mutant huntingtin protein that results in Huntington disease

A) causes a decrease in production of another protein.
B) leads to degeneration of cells in the brain's striatum.
C) is toxic to brain cells.
D) leads to degeneration of cells in the brain's striatum and is toxic to brain cells only.
E) has all of these traits.

Question 12

Which of the following proteins is NOT involved with Huntington disease?

A) Huntingtin
B) Rhes
C) BDNF
D) MAOA
E) All of these are proteins involved in Huntington disease

Question 13

What is the underlying molecular cause of Huntington disease?

A) The binding of a normal protein to a mutant protein making it cytotoxic.
B) Two mutant proteins in combination produce a toxic precipitate.
C) Normal proteins fold the wrong way, creating plaques that are cytotoxic.
D) mRNA molecules are degraded before they can be properly translated.
E) tRNA molecules fail to bind strongly enough with their associated amino acids.

Question 14

A mutation in the MAOA gene is associated with ____________ behavior.

A) fear-based
B) risk-taking
C) violent
D) schizophrenic
E) bipolar

Question 15

The environmental contribution to bipolar disorder is most likely, at least in part, based on _____________.

A) prenatal exposure to toxic chemicals
B) overexposure to UV light
C) mutagens that damage DNA repair enzymes
D) epigenetic changes involving methylation and demethylation
E) childhood abuse

Question 16

Many human behavioral traits

A) show genetic heterogeneity with the same phenotype resulting from different genes.
B) are due to dominant genes.
C) are a result of mutations in structural genes.
D) show genetic heterogeneity with the same phenotype resulting from different genes and are due to dominant genes.
E) none of these.

Question 17

Huntington disease is

A) a model of a multifactorial trait, controlled by several genes.
B) inherited as an X-linked dominant trait.
C) a disease with onset in early childhood.
D) one that produces no significant changes in brain cells.
E) a model of a single gene defect affecting behavior.

Question 18

The only gene that has been positively identified with the onset of Alzheimer disease encodes a protein that ___________________.

A) is involved in cholesterol metabolism
B) breaks down neurotransmitters
C) maintains the health of striatum cells
D) attaches amino acids to tRNA molecules
E) breaks down fatty deposits around neurons

Question 19

For which of the following diseases would animal models likely yield the most information?

A) Alcoholism
B) Schizophrenia
C) Bipolar disorder
D) Huntington disease
E) PKU

Question 20

Studies of CNVs (copy number variations) reveal that schizophrenia and autism may be ______________.

A) the same disorder
B) opposite faces of the same disorder
C) always inherited together
D) linked to bipolar disorder
E) X-linked dominant disorders

Question 21

The FOXP2 gene that has been associated with a language disorder codes for a ____________________, which is a protein that switches on genes.

Question 22

The normal form of huntingtin protein enhances the production of another protein, _________________.

Question 23

Amyloid plaques are routinely found in many brains but are much more common in the brains of people who have ____________________.

Question 24

It is difficult to decide whether many behaviors should be considered abnormal behaviors or just variants.

Question 25

A 15 percent concordance rate in MZ twins, with a 8 percent rate in same-sex DZ twins, indicates that genes play a major role in a trait.

Question 26

Huntington disease involves multiple trinucleotide repeats of the nucleotide sequence _____________.

Question 27

The so-called language gene is a transcription factor called _____________.

Question 28

Transgenic mice carrying a mutant human SOD1 gene are used as models to study ____________________.

Question 29

Linkage studies are sufficient to establish the genetic basis of a behavioral trait.

Question 30

The FOXP2 gene encodes a protein involved in aggressive behavior.

Question 31

A pattern of earlier onset of a disease along with more severe symptoms is called ________________.

Question 32

Genome screening with molecular markers is a useful model for studying the genetics of homosexuality.

Question 33

People carrying less than 35 CAG trinucleotide repeats are more likely to develop Huntington disease.

Question 34

Schizophrenia has been shown to be a single gene disorder.

Question 35

The gene associated with aggressive behavior identified in 1993 is to be linked to an enzyme called ____________________.

Question 36

The lesions in the brains of people with Alzheimer disease are caused by a protein fragment called ___________________.

Question 37

The FOXP2 gene encodes a transcription factor and has been shown to be important for ______________ development.

Question 38

Alleles at different loci can interact in a non-additive fashion in some behavioral traits.

Question 39

All behavioral traits have an early onset.

Question 40

MAOA is an enzyme that breaks down ______________.

Question 41

Outline some of the difficulties in studying the genetics of human behavior traits.

Question 42

Association studies compare affected individuals from different families with unaffected individuals, seeking to find genetic differences between those with and without a behavior disorder. Given the size and complexity of the human genome, do you think this approach can be used to systematically scan the genome for loci controlling behavior? How will you know when you have found one? How do you differentiate between polymorphisms and genuine differences?

Question 43

Alcohol dehydrogenase converts alcohol into _____________________.

Question 44

An early model of bipolar illness postulated that a single gene was responsible for the phenotype. This led to the "discovery" of a locus on chromosome 11 thought to be the gene responsible for this behavioral abnormality. Further work caused the retraction of this discovery, but the issues raised in this case have not been fully resolved. What are the problems associated with a single gene model, and how do they affect the search for the gene?

Question 45

Alcoholism has been proposed as a genetically controlled or influenced trait. Outline some of the difficulties in studying the genetics of this behavior trait, beginning with the definition of the phenotype. Can you define the problem in such a way that will provide a hypothesis as to the nature of the disorder, allowing a genetic approach to be mounted?

Question 46

Some have proposed that alcoholism is not a specific trait but only one manifestation of a trait called "addictive personality" that would include other drug addictions and habits. What have you learned about alcoholism that would make this proposal seem reasonable? How could research on alcoholism be changed to test this hypothesis?

Question 47

Emphasis is now being placed on the relationship between abnormalities in neurotransmitters and altered social behavior. Does it seem likely that metabolic differences can alter only behavior, and not produce effects on other systems such as muscle movement and coordination? How do you reconcile such apparent contradictions?

Question 48

Give evidence that might prove that human personality could be partially inherited.

Question 49

Sexual orientation (heterosexual, homosexual, or bisexual) may be a multifactorial trait involving several genes and unidentified environmental components. Read the paper by Hamer, et al., (1993 Science 261: 321-327) on male sexual orientation and outline the steps taken in constructing this study. Do you think these steps biased the outcome in any way? Why or why not?

Question 50

Discuss the tools used to see if human behavior has a genetic component, and give two examples of either normal or abnormal behavior that appears to have a genetic component.

Question 51

How are twins used in research behavioral traits?