Deck 24: Neurogenetics

Question 1

List at least three areas of research that deal with the genetics of behavior in humans.

Answer 1

Huntington disease, fragile X syndrome, autism

Question 2

Briefly describe the mutant status of the HD gene.

Answer 2

The HD gene encodes a 350 kd protein (huntingtin) in which mutant alleles have extra CAG trinucleotide repeats near the 5' end. Normal individuals have 7 to 34 repeats, whereas those with HD carry more than 40 repeats.

Question 3

Suggest two problems with determining the genetic basis of a behavioral trait in humans.

Answer 3

influence of the environment and difficulty in conducting genetic studies on humans

Question 4

Determining the genetic influence on two fairly common human behavioral disorders has eluded researchers for many years. One involves passive deficits in thinking, language, feelings, and social skills; the other includes a variety of psychotic symptoms, perceptual disorders (hearing voices), and withdrawal from reality. Evidence from pedigrees and twins indicates that these two behaviors have a genetic component. Which behaviors are being described here?

Question 5

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

Question 6

Huntington disease (HD) is a well-studied, autosomal dominant disorder that affects the nervous system. Symptoms usually appear after age 40, and victims usually die within 10 to 15 years after onset of the disease. It appears that at least in some cases of HD, "stutter" mutations occur. Such mutations are characterized by ________.

A) uncontrolled verbal capacity of patients
B) extra trinucleotide repeats within the HD gene
C) RNA polymerase imperfections leading to altered DNAs
D) repeated DNA polymerases generating too many coding symbols
E) links between monoamine oxidase A (MAOA) and hexokinase

Question 7

What is the biochemical role of adenyl cyclase?

Question 8

Fragile X syndrome is a neurological disorder that is caused by a dominantly inherited mutant allele on the X chromosome?

Question 9

Humans are relatively unavailable as experimental subjects in genetic investigations, yet considerable interest surrounds intelligence, language, personality, and emotional behaviors. One difficulty in studying such behaviors is the high likelihood that they ________.

A) are strongly influenced by birth order and diet
B) are affected by the environment
C) follow non-Mendelian patterns of inheritance
D) follow extranuclear patterns of inheritance
E) have no likely genetic influence

Question 10

How are electrical impulses propagated from neuron to neuron?

Question 11

What anatomical structure is responsible for the transfer of impulses between neurons?

Question 12

Present an overview of the research dealing with the genetics of behavior in small mammals (mice or rats) and Drosophila.

Question 13

Recent research using gene expression profiles indicates that schizophrenia and autism spectrum disorders are ________.

A) like opposite sides of the same coin
B) identical at the molecular level
C) completely unrelated
D) likely to be caused by the same dominant gene
E) likely to be caused by the same recessive gene

Question 14

The HD gene, one of the first genes to be mapped in humans by RFLP, is located on the short arm of chromosome 4. It codes for ________.

Question 15

What is a major problem that arises in the study of the genetic basis of human behavior?

A) Memories of individuals are unreliable.
B) People are too short lived.
C) Behaviors are difficult to define objectively.
D) The environment plays no role in behavioral expression.
E) The environment is the only factor that determines human behavior.

Question 16

Why is cyclic AMP considered important in behavioral studies?

Question 17

Much effort has been expended to understand genetic involvement in brain function in Drosophila. Why might this research be important in understanding the functioning of the human brain?

Question 18

Autism spectrum disorders are neurodevelopmental disorders that appear to be ________.

A) caused by a single dominant gene
B) multifactorial and complex in nature with a genetic component
C) caused by several genes located on the X chromosome
D) caused by a low number of recessive genes located mainly on the autosomes
E) directly related to trinucleotide repeat increases but not decreases

Question 19

What conclusion has been reached regarding the genetic status of schizophrenia using genome-wide association studies?

A) A single dominant gene is involved.
B) No single gene or allele makes a significant contribution.
C) A single recessive gene is involved.
D) Several dominant genes located on the X chromosome cause this disease.
E) No more than three loci are involved in the expression of schizophrenia.

Question 20

One of the oldest recorded behavior mutants is the waltzer mutation in the mouse. Mutant mice can be observed "dancing" and "head shaking"; some are also deaf. Mice must be homozygous for a mutation to express the trait. Based on this information, the genetic cause of this trait is most likely a(n) ________.

A) simple recessive pattern of inheritance
B) multifactor, polygenic pattern of inheritance
C) dominant/recessive pattern typical of other behavioral traits
D) epistatic pattern with incomplete dominance
E) variable gene activity pattern with overdominance causing deafness

Question 21

Individuals with Huntington disease have a point mutation in a gene coding for the p53 protein.

Question 22

Research on alcoholism indicates that at least in mouse and animal models, a single dominant gene is responsible.

Question 23

Drosophila can learn and remember.

Question 24

Evidence from genome-wide association studies on schizophrenia indicates that no single gene or allele makes a significant contribution to this disorder.

Question 25

Mitochondrial ribosomes are responsible for determining the learning and memory development in Drosophila.

Question 26

In studies attempting to determine a genetic basis for a given behavior, if the environment is held constant, and behavioral differences directly correlate with genetic differences, a genetic basis for the behavioral state is supported.

Question 27

The symptoms of Huntington disease usually appear in the third to fifth decade of life in humans.

Question 28

A transgenic mouse model now exists for Huntington disease in humans.

Question 29

The availability of a large series of monozygotic and dizygotic twins often enhances studies on the genetic basis of human behavior.