Deck 4: Gene Function

Question 1

What was the significance of Beadle and Tatum's experiment?

A)It resulted in the central dogma.
B)It led to the discovery of bread mold.
C)It resulted in the one-gene-one-enzyme hypothesis.
D)It led to the discovery of the genetic code.
E)It proved that X-rays were mutagens.

Answer 1

C

Question 2

In a molecule of hemoglobin C,an aspartic acid residue is changed into a ________ residue.

A)lysine
B)tyrosine
C)leucine
D)phenylalanine
E)glutamine

Answer 2

A

Question 3

Amniocentesis involves

A)prenatal diagnosis of genetic defects in a fetus.
B)tests for enzyme and protein deficiencies in a fetus.
C)taking a sample of amniotic fluid with a needle.
D)analysis for DNA and chromosome defects in a fetus.
E)All of these

Answer 3

E

Question 4

Why did Garrod define alkaptonuria as a recessive genetic disease?

A)It is expressed in male members of an affected family.
B)It is expressed in all members of an affected family.
C)It is expressed under certain environmental conditions.
D)It is expressed when two alleles for the disease are present.
E)It is expressed when one of the two alleles carries the disease trait.

Question 5

Individuals with Lesch-Nyhan syndrome exhibit

A)urine that turns black when exposed to air.
B)compulsive self-mutilation behaviors.
C)lighter than normal pigmentation of skin,hair,and eyes.
D)severe anemia.
E)a cherry-colored spot on the retina.

Question 6

Normal and sickle-cell hemoglobin molecules differ

A)in the number of amino acids in each molecule.
B)by a single DNA point mutation that leads to the substitution of one amino acid for another.
C)in the number and orientation of the amino acid chains attached to the heme portion of each molecule.
D)in the number of oxygen molecules that can be carried by each molecule.
E)by the type of bone marrow that produces them.

Question 7

A mutation that has pleiotropic consequences

A)results in a single symptom in the affected person.
B)may result in only slight symptoms in a person with the mutation.
C)is only detected in homozygotes.
D)has widespread consequences in the affected person.
E)cannot be detected by enzyme assay.

Question 8

A lysosomal storage disease is caused by

A)failure of the cell to produce lysosomes.
B)the inability to synthesize glycolipids.
C)mutations in genes for lysosomic membrane proteins.
D)an excess in the production of lysosomic digestive enzymes.
E)mutations in genes that code for lysosomic digestive enzymes.

Question 9

Which of the following is a sex-linked disorder?

A)Lesch-Nyhan syndrome
B)Alkaptonuria
C)Albinism
D)Down syndrome
E)Tay-Sachs disease

Question 10

A carrier for a disease

A)is homozygous for the dominant mutation.
B)is homozygous for the recessive mutation.
C)is heterozygous for the dominant mutation.
D)is heterozygous for the recessive mutation
E)is hemizygous for any mutation.

Question 11

Which genetic disease(s)are caused by defective proteins that are not enzymes?

A)Tay-Sachs disease and phenylketonuria
B)Sickle-cell anemia and cystic fibrosis
C)Lesch-Nyhan syndrome.
D)Albinism and alkaptonuria
E)All of these

Question 12

Auxotrophs are organisms that can grow

A)on minimal media.
B)on complete media.
C)only on amino acid supplemented media.
D)only on vitamin supplemented media.
E)on any media.

Question 13

In people who do not have Tay-Sachs disease,the hexA gene encodes an enzyme that

A)converts purines to uric acid in the kidneys.
B)removes a sugar group from phenylalanine.
C)converts tyrosine to melanin in skin.
D)cleaves acetylgalactosamine from gangliosides.
E)synthesizes glycogen from glucose monomers.

Question 14

A person with sickle-cell trait has ________ at the β-globin locus.

A)two wild-type alleles
B)two mutant alleles
C)one wild-type and one mutant allele
D)one wild-type and one deleted allele
E)one mutant and one deleted allele

Question 15

The cystic fibrosis gene (CFTR)codes for a protein that is essential for

A)secretion of mucus.
B)ion transport across membranes.
C)transport of oxygen in red blood cells.
D)metabolism of certain amino acids.
E)processing of gangliosides.

Question 16

A mutagen is

A)the process that generates mutants.
B)the agent that induces mutants.
C)the mutants that are generated by an agent.
D)the experiment that generates mutants.
E)the process that corrects mutants.

Question 17

Which of the following statements about phenylketonuria (PKU)is false?

A)Buildup of phenylpyruvic acid affects the nervous system.
B)The amino acid tyrosine cannot be made.
C)Production of the hormone thyroxin s affected.
D)The skin color of those with phenylketonuria is light because of decreased levels of melanin.
E)Adrenalin levels increase in the blood stream.

Question 18

What does a gene actually code for?

A)A polypeptide
B)An enzyme
C)An amino acid
D)A protein
E)A nucleotide

Question 19

Cystic fibrosis is caused by a mutation in the gene that encodes which enzyme?

A)Pyruvate kinase
B)CFTR protein
C)Hexosaminidase A
D)Hemoglobin
E)Tyrosine kinase

Question 20

Genetic counseling is the best advice that a physician can give a person about his or her risk of having a child with a genetic disorder while lacking precise statistical evidence.

Question 21

How do scientists,lacking the ability to make controlled genetic crosses in humans,study the inheritance of and give genetic counseling on human genetic disorders?

Question 22

The Guthrie test screens for excessive phenylalanine in the blood of infants.

Question 23

What is an inborn error of metabolism? Give an example.

Question 24

Cystic fibrosis is an autosomal recessive disorder.What is the chance that two carrier parents will have an affected child?

A)100%
B)75%
C)50%
D)25%
E)0%

Question 25

Sickle-cell disease is more common among people who are of African rather than European descent.

Question 26

You discover a mutant strain of Neurospora crassa that will not grow on a minimal medium but that will grow on a medium supplemented by the amino acid methionine.How can you determine which step in the methionine synthesis pathway is affected by the mutation?

Question 27

What is an essential amino acid? Give an example.

Question 28

A Neurospora mutant that is a tryptophan auxotroph does not need to be grown on a medium that contains tryptophan.

Question 29

The sickle-cell mutant allele and wild-type β-globin allele are codominant.

Question 30

Tay-Sachs disease is most prevalent among populations of the Pennsylvania Amish in the United States.

Question 31

Albinism is caused by an inborn error of metabolism.

Question 32

Cystic fibrosis is a pleiotropic disease.

Question 33

Why are genetic diseases much more common among children of marriages involving first cousins than among children of marriages between unrelated partners?

Question 34

Because Lesch-Nyhan syndrome is a recessive X-linked disease,females who have an allele with the mutation responsible for this disease are generally symptom-free.

Question 35

A person who is homozygous for the gene for hemoglobin A will have sickle-cell disease.

Question 36

A person with PKU controls the buildup of phenylpyruvic acid in his or her blood by restricting dietary intake of phenylalanine,thus avoiding the severe symptoms of mental retardation,slow growth rate,and early death.Yet he or she still exhibits the symptoms of fair skin and low adrenaline levels.Why?

Question 37

The following is a representation of a metabolic pathway that involves genes for enzymes A,B,C,and D: A → B → C → D → product
A mutation in the B gene would result in an accumulation of which gene product?

Question 38

In the laboratory,how could you distinguish between normal hemoglobin A and hemoglobin S?

Question 39

What factor do the diseases PKU,albinism,and alkaptonuria all have in common?

Question 40

What advantages does chorionic villus sampling have over amniocentesis for fetal analysis of genetic defects?

Question 41

Classic albinism is an autosomal recessive mutation.However,two parents with albinism may produce a child with normal pigment.How can this be so?

Question 42

How can enzyme assay be used to detect carriage of a recessive gene mutation in a person of normal phenotype?

Question 43

While the defective gene product in patients with PKU was identified using biochemical analysis,how was the cystic fibrosis gene identified?

Question 44

You are a doctor who specializes in genetic diseases.A married couple comes to see you for genetic counseling.The woman has PKU,the symptoms of which she manages by diet.The man and woman are first cousins and would like to know the probability that any of their children will have the disease.What would you tell them?

Question 45

Explain the difference between the one-gene-one-enzyme hypothesis and the one-gene-one-polypeptide hypothesis.