Test Bank For iGenetics A Molecular Approach 3rd Edition by Peter J. Russell

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Test Bank For iGenetics A Molecular Approach 3rd Edition by Peter J. Russell

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WITH ANSWERS

iGenetics A Molecular Approach 3rd Edition by Peter J. Russell Test Bank 

 

iGenetics: A Molecular Approach, 3e (Russell/Bose)

Chapter 2   DNA: The Genetic Material

 

MATCHING

 

Please select the best match for each term.

 

  1. A) The basic structural unit of chromatin with bead-on-a-string morphology
  2. B) The region of a eukaryotic chromosome found near the attachment point of mitotic or meiotic spindle fibers
  3. C) A DNA molecule and associated proteins
  4. D) The constituent monomer of DNA and RNA
  5. E) The region of a prokaryotic cell where the chromosome is located

 

1) Centromere

Skill:  Factual recall

 

2) Nucleoid

Skill: Factual recall

 

3) Nucleotide

Skill: Factual recall

 

4) Chromosome

Skill:  Factual recall

 

5) Nucleosome

Skill:  Factual recall

 

Answers: 1) B 2) E 3) D 4) C 5) A

 

 

MULTIPLE CHOICE

 

6) Loosely aggregated DNA bound to proteins in a eukaryotic cell is called

  1. A) chromosomes.
  2. B) chromatin.
  3. C) chromatid.
  4. D) centromere.
  5. E) nucleoid.

Answer:  B

Skill:  Factual recall

 

7) The C-value is the amount of DNA in a

  1. A) haploid genome.
  2. B) diploid genome.
  3. C) bacterial genome.
  4. D) eukaryotic genome.
  5. E) cells nucleus.

Answer:  A

Skill:  Factual recall

8) The chromosome of most prokaryotes differs from those of eukaryotes in that

  1. A) the prokaryotic chromosome is linear, while the eukaryotic chromosome is circular.
  2. B) the prokaryotic chromosome is circular, while the eukaryotic chromosome is linear.
  3. C) the prokaryotic chromosome does not replicate before mitosis, while the eukaryotic chromosome does.
  4. D) the prokaryotic chromosome does not contain genes, while the eukaryotic chromosome does.
  5. E) the prokaryotic chromosome is not necessary for the organisms survival, while the eukaryotic chromosome is.

Answer:  B

Skill:  Factual recall

 

9) A Barr body is an example of

  1. A) constitutive euchromatin.
  2. B) facultative euchromatin.
  3. C) facultative heterochromatin.
  4. D) a nucleosome.
  5. E) constitutive heterochromatin.

Answer:  C

Skill:  Factual recall

 

10) The definition of transformation is

  1. A) the shift of genetic information from DNA to protein.
  2. B) the genetic alteration of an organism.
  3. C) the uptake of genetic information by a cell from the environment.
  4. D) Both B and C
  5. E) None of these

Answer:  D

Skill:  Factual recall

 

11) In Griffiths experiment involving the transformation of Streptococcus pneumoniae,

  1. A) the R strain was virulent.
  2. B) the S strain was virulent.
  3. C) both the R and S strains were virulent.
  4. D) the R strain had a protein capsule.
  5. E) the S strain had a protein capsule.

Answer:  B

Skill:  Factual recall

 

12) What was the transforming principle isolated in Griffiths experiment?

  1. A) Protein
  2. B) RNA
  3. C) DNA
  4. D) Virus
  5. E) Polysaccharide

Answer:  C

Skill:  Factual recall

13) Who used radioactively labeled T2 bacteriophage to confirm the identity of the transforming principle?

  1. A) Griffith
  2. B) Hershey and Chase
  3. C) Avery
  4. D) Gierer and Schramm
  5. E) Beadle and Tatum

Answer:  B

Skill:  Factual recall

 

14) Which part of the T2 bacteriophage entered E. coli cells in the experiment which confirmed the identity of the transforming principle?

  1. A) The RNA
  2. B) The DNA
  3. C) The whole virus
  4. D) The protein coat
  5. E) No part

Answer:  B

Skill:  Factual recall

 

15) Certain ________ have RNA for their genetic material.

  1. A) bacteria
  2. B) viruses
  3. C) plants
  4. D) eukaryotes
  5. E) prokaryotes

Answer:  B

Skill:  Factual recall

 

16) What did the X-ray diffraction patterns initially reveal about the DNA molecule?

  1. A) It is of uniform diameter and has a helical structure.
  2. B) It is a helical molecule with paired bases in the center.
  3. C) It is double-stranded with antiparallel strands.
  4. D) It is acidic, phosphorus-rich, and large.
  5. E) It contains hereditary information.

Answer:  A

Skill:  Factual recall

 

17) What did Watson and Crick deduce about the three-dimensional structure of DNA?

  1. A) There is a repeating pattern every 3.4 nm and every 0.34 nm.
  2. B) It is a double-stranded helix.
  3. C) It contains a lot of phosphorus.
  4. D) It is a large molecule.
  5. E) It consists of supercoiled chromatin.

Answer:  B

Skill:  Factual recall

18) Which of the following is a nonhistone protein found in chromatin?

  1. A) H1
  2. B) HMG
  3. C) H2A
  4. D) H5
  5. E) All of these

Answer:  B

Skill:  Factual recall

 

19) Antiparallel means that

  1. A) the two polynucleotide chains run in opposite directions.
  2. B) each DNA molecule consists of one old and one new strand.
  3. C) opposite strands are held together by base pairing.
  4. D) the helix twists to the right.
  5. E) there is complementary base-pairing.

Answer:  A

Skill:  Factual recall

 

20) Complementary base-pairing allows for

  1. A) spontaneous mutations to occur.
  2. B) genes to be expressed as a phenotype.
  3. C) DNA to serve as its own template for replication.
  4. D) replication to be semiconservative.
  5. E) covalent bonds to form between the opposite bases.

Answer:  C

Skill:  Factual recall

 

 

21) Which of the following are the purine nucleotides in DNA?

  1. A) Adenine and thymine
  2. B) Cytosine and guanine
  3. C) Adenine and cytosine
  4. D) Guanine and adenine
  5. E) Thymine and uracil

Answer:  D

Skill:  Factual recall

 

22) Topoisomerases function to

  1. A) remove nucleotides from DNA.
  2. B) join DNA pieces together.
  3. C) twist DNA
  4. D) attach DNA loops to scaffold proteins.
  5. E) move chromosomes along spindle fibers.

Answer:  C

Skill:  Factual recall

23) Which form of DNA is a left-handed double helix?

  1. A) A-DNA
  2. B) B-DNA
  3. C) L-DNA
  4. D) R-DNA
  5. E) Z-DNA

Answer:  E

Skill:  Factual recall

 

24) The displacement loop (D-loop) may be a characteristic of

  1. A) centromeres.
  2. B) telomeres.
  3. C) A-DNA.
  4. D) B-DNA.
  5. E) Z-DNA.

Answer:  B

Skill:  Factual recall

 

25) Which nucleotide is absent in RNA?

  1. A) Adenine
  2. B) Guanine
  3. C) Uracil
  4. D) Cytosine
  5. E) Thymine

Answer:  E

Skill:  Factual recall

 

 

TRUE/FALSE

 

26) DNA and RNA both contain phosphate and ribose.

Answer:  FALSE

Explanation:  They both contain phosphate, but DNA contains the sugar deoxyribose rather than ribose.

Skill:  Factual recall

 

27) Hershey and Chase used radioactive sulfur to label the genetic material of bacteriophages.

Answer:  FALSE

Explanation:  The radioactive sulfur labeled the protein coat.

Skill:  Factual recall

 

28) In a strand of DNA, a hydrogen bond connects the phosphate group of one nucleotide to the sugar of the adjacent nucleotide.

Answer:  FALSE

Explanation:  A covalent phosphodiester bond connects the two adjacent nucleotides.

Skill:  Factual recall

 

29) The genome of the T-even family of bacteriophage consists of single-stranded RNA.

Answer:  FALSE

Explanation:  It consists of double-stranded DNA.

Skill:  Factual recall

30) Borrelia burgdorferi is a bacterium whose genome consists of one large and several small linear chromosomes.

Answer:  TRUE

Skill:  Factual recall

 

31) By weight, the amount of DNA in chromatin is less than that of histone.

Answer:  FALSE

Explanation:  The weights of DNA and histone in chromatin are equal.

Skill:  Factual recall

 

32) The virus first shown to have RNA as its genetic material was tobacco mosaic virus (TMV).

Answer:  TRUE

Skill:  Factual recall

 

33) The more condensed a part of a chromosome is, the more likely it is that the genes in that region will be active.

Answer:  FALSE

Explanation:  The genes in a region are less likely to be active the more condensed a part of a chromosome is.

Skill:  Factual recall

 

 

34) The genome of most prokaryotes consists of moderately repetitive DNA.

Answer:  FALSE

Explanation:  The genome of most prokaryotes consists of unique-sequence DNA.

Skill:  Factual recall

 

35) In eukaryotes, the greatest relative amount of tandemly repeated DNA is associated with centromeres and telomeres.

Answer:  TRUE

Skill:  Factual recall

 

SHORT ANSWER

 

36) In Griffiths transformation experiments, under what conditions did the injected mice die?

Answer:  The mice died when they were injected with living, virulent bacteria, and when they were injected with living, nonvirulent bacteria mixed with heat-killed, virulent bacteria.

Skill:  Factual recall

 

37) How could you test whether the transforming ability of a cell extract was due to DNA or RNA?

Answer:  You could treat the extract with a DNase or RNase enzyme and test whether its transforming ability was intact.

Skill:  Application of knowledge

 

38) One of the strands in a DNA double helix has the nucleotide sequence 5-ACCTGCTACGG-3. What is the sequence of the complementary DNA strand?

Answer:  3-TGGACGATGCC-5

Skill:  Problem-solving

39) What is the function of dispersed repeated sequences such as SINEs and LINEs in eukaryotes?

Answer:  Little is known about the function of such sequences, but one hypothesis is that they have no function at all. Another is that they are involved in regulating gene expression.

Skill:  Factual recall

 

40) What is the C-value paradox, and what is its cause?

Answer:  There is also no direct relationship between the C-value (the total amount of DNA in the haploid genome) and the structural or organizational complexity of the organism. This is due in part to the amount of repetitive-sequence DNA found in the genome of some organisms.

Skill:  Conceptual understanding

 

41) Define Chargaffs rules of the base composition of DNA.

Answer:  Chargaffs rules include the following: (1) the amount of adenine = the amount of thymine, (2) the amount of guanine = the amount of cytosine, and (3) the amount of purines = the amount of pyrimidines.

Skill:  Factual recall

 

 

42) Describe the differences between heterochromatin and euchromatin in chromosomes. Are there any situations in which one can be changed into the other?

Answer:  Euchromatin contains actively transcribed genes and undergoes normal cycles of condensation and decondensation in the cell cycle. Heterochromatin remains condensed and contains genes that are usually transcriptionally inactive. Euchromatin can be inactivated, as in the case of Barr bodies. It is then known as facultative heterochromatin.

Skill:  Factual recall

 

43) What are the three necessary characteristics of the hereditary molecule in cells?

Answer:  (1) It must be able to carry information, (2) it must be able to accurately pass on the information to progeny cells (replicate), and (3) it must be capable of change (evolution).

Skill:  Conceptual understanding

 

44) Name the constituent parts of a nucleoside and a nucleotide.

Answer:  A nucleoside consists of a pentose sugar covalently bonded to a nitrogenous base; a nucleotide is a nucleoside with the addition of a phosphate group.

Skill:  Factual recall

 

45) The DNA phage 174 was found to have a ratio of bases of 25A:33T:24G:18C. This departs from the usual A/T = 1 and G/C = 1 ratios. How can you explain this?

Answer:  The genome of the phage consists of single-stranded, rather than double-stranded, DNA.

Skill:  Conceptual understanding

 

46) If the human egg has 3 billion base pairs, how many nucleosomes will be present in the nucleus of a human somatic cell?

Answer:  In humans, the DNA wrapped around each nucleosome is approximately 200 bp (147 bp + 53 bp linker). As such, there will be approximately 3  109/2  102 = 1.5 107 nucleosomes in a human egg nucleus. However, the egg is haploid, whereas the somatic cells are diploid. Therefore, there will be approximately 1.5 107  2 = 3 107 nucleosomes in the nucleus of a human somatic cell.

Skill:  Problem-solving

47) Why are the amino acid sequences of eukaryotic histones so similar to one another, even among distantly related species?

Answer:  Evolutionary conservation of these sequences is a strong indicator that histones perform the same basic role in organizing the DNA in the chromosomes of all eukaryotes.

Skill:  Conceptual understanding

 

48) Describe the packing of chromatin from the 10-nm to the 30-nm fiber stage. What is the role of histones?

Answer:  10-nm chromatin fiber consists of nucleosomesbeads of DNA wound around eight core histone proteinsconnected by strands of linker DNA. The 30-nm chromatin fiber is created by the binding of histone H1, which brings the linker DNA and the nucleosomes closer together. In the solenoid model of the 30-nm fiber, the nucleosomes are brought together into a spiraling helical structure, with about six nucleosomes per complete turn.

Skill:  Conceptual understanding

 

49) What is the role of centromeres and telomeres?

Answer:  Centromeres are the chromosomal regions where mitotic or meiotic spindle fibers attach. They are therefore responsible for the accurate segregation of chromosomes to daughter cells during replication. Telomeres are heterochromatic regions of chromosomes that are also required for replication and stability. They are usually found at the ends of the chromosome and are associated with the nuclear envelope.

Skill:  Factual recall

 

50) If the base pairs in a DNA helix are 0.34 nm apart, and a complete (360) turn of the helix takes 3.4 nm, how many base pairs per turn are there in a DNA molecule?

Answer:  There are 10 base pairs per turn.

Skill:  Problem-solving

iGenetics: A Molecular Approach, 3e (Russell/Bose)

Chapter 4   Gene Function

 

MATCHING

 

Please select the best match for each term.

 

  1. A) Hexosaminidase A
  2. B) Galactose-1-phosphate uridyl transferase
  3. C) Homogentisic acid oxidase
  4. D) Hypoxanthine guanine phosphoribosyltransferase
  5. E) Fructose-1,6-diphosphatase

 

1) Alkaptonuria

Skill: Factual recall

 

2) TaySachs disease

Skill:  Factual recall

 

3) LeschNyhan syndrome

Skill:  Factual recall

 

4) Galactosemia

Skill:  Factual recall

 

5) Hypoglycemia

Skill:  Factual recall

 

Answers: 1) C 2) A 3) D 4) B 5) E

 

 

MULTIPLE CHOICE

 

6) Why did Garrod define alkaptonuria as a recessive genetic disease?

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

Answer:  D

Skill:  Factual recall

 

7) What was the significance of Beadle and Tatums experiment?

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

Answer:  C

Skill:  Factual recall

 

8) What does a gene actually code for?

  1. A) A polypeptide
  2. B) An enzyme
  3. C) An amino acid
  4. D) A protein
  5. E) A nucleotide

Answer:  A

Skill:  Factual recall

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

  1. A) TaySachs disease and phenylketonuria
  2. B) Sickle-cell anemia and cystic fibrosis
  3. C) LeschNyhan syndrome.
  4. D) Albinism and alkaptonuria
  5. E) All of these

Answer:  B

Skill:  Factual recall

 

10) Amniocentesis involves

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

Answer:  E

Skill:  Factual recall

 

 

11) Auxotrophs are organisms that can grow

  1. A) on minimal media.
  2. B) on complete media.
  3. C) only on amino acid supplemented media.
  4. D) only on vitamin supplemented media.
  5. E) on any media.

Answer:  B

Skill:  Factual recall

 

12) A lysosomal storage disease is caused by

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

Answer:  E

Skill:  Factual recall

 

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

  1. A) Pyruvate kinase
  2. B) CFTR protein
  3. C) Hexosaminidase A
  4. D) Hemoglobin
  5. E) Tyrosine kinase

Answer:  B

Skill:  Factual recall

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

  1. A) lysine
  2. B) tyrosine
  3. C) leucine
  4. D) phenylalanine
  5. E) glutamine

Answer:  A

Skill:  Factual recall

 

15) A mutation that has pleiotropic consequences

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

Answer:  D

Skill:  Factual recall

 

 

16) Individuals with LeschNyhan syndrome exhibit

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

Answer:  B

Skill:  Factual recall

 

17) A mutagen is

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

Answer:  B

Skill:  Factual recall

 

18) In people who do not have TaySachs disease, the hexA gene encodes an enzyme that

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

Answer:  D

Skill:  Factual recall

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

  1. A) two wild-type alleles
  2. B) two mutant alleles
  3. C) one wild-type and one mutant allele
  4. D) one wild-type and one deleted allele
  5. E) one mutant and one deleted allele

Answer:  C

Skill:  Factual recall

 

20) Which of the following is a sex-linked disorder?

  1. A) LeschNyhan syndrome
  2. B) Alkaptonuria
  3. C) Albinism
  4. D) Down syndrome
  5. E) TaySachs disease

Answer:  A

Skill:  Factual recall

 

 

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

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

Answer:  E

Skill:  Factual recall

 

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

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

Answer:  B

Skill:  Factual recall

 

23) A carrier for a disease

  1. A) is homozygous for the dominant mutation.
  2. B) is homozygous for the recessive mutation.
  3. C) is heterozygous for the dominant mutation.
  4. D) is heterozygous for the recessive mutation
  5. E) is hemizygous for any mutation.

Answer:  D

Skill:  Factual recall

24) Normal and sickle-cell hemoglobin molecules differ

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

Answer:  B

Skill:  Factual recall

 

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

  1. A) 100%
  2. B) 75%
  3. C) 50%
  4. D) 25%
  5. E) 0%

Answer:  D

Skill:  Problem-solving

 

 

TRUE/FALSE

 

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

Answer:  FALSE

Explanation:  A tryptophan auxotroph cannot synthesize its own tryptophan. It should be grown on a medium that contains tryptophan.

Skill:  Factual recall

 

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

Answer:  TRUE

Skill:  Factual recall

 

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

Answer:  FALSE

Explanation:  If her normal allele has undergone lyonization (random X inactivation), the carrier female may display symptoms.

Skill:  Factual recall

 

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

Answer:  FALSE

Explanation:  This person will have normal hemoglobin and normal red blood cells.

Skill:  Factual recall

 

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

Answer:  TRUE

Skill:  Factual recall

31) Albinism is caused by an inborn error of metabolism.

Answer:  TRUE

Skill:  Factual recall

 

32) 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.

Answer:  FALSE

Explanation:  If knowledge about the role of heredity in a genetic disorder is lacking, genetic counseling can only give a general estimate of risk. In many circumstances, however, the physician can give a person precise probabilities about the risk of passing on a genetic defect.

Skill:  Factual recall

 

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

Answer:  TRUE

Skill:  Factual recall

 

 

34) Cystic fibrosis is a pleiotropic disease.

Answer:  TRUE

Skill:  Factual recall

 

35) TaySachs disease is most prevalent among populations of the Pennsylvania Amish in the United States.

Answer:  FALSE

Explanation:  It is most prevalent among Ashkenazi Jews of central and eastern European descent.

Skill:  Factual recall

 

SHORT ANSWER

 

36) 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?

Answer:  A

Skill:  Analytical reasoning

 

37) What is an essential amino acid? Give an example.

Answer:  An essential amino acid is one that humans must consume as part of their diet, because they are unable to synthesize it. An example is phenylalanine.

Skill:  Conceptual understanding

 

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

Answer:  The two forms of hemoglobin have different electrical charges. Therefore, you could distinguish between them by their migration patterns on an electrophoresis gel.

Skill:  Application of knowledge

39) 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?

Answer:  The PKU mutation is in the gene for phenylalanine hydroxylase, the enzyme that converts phenylalanine to tyrosine. Tyrosine is essential for melanin and adrenaline production. A PKU individual cannot make tyrosine, and it is difficult to obtain enough tyrosine from food intake to avoid any symptoms of the disease.

Skill:  Analytical reasoning

 

 

40) 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?

Answer:  Pedigree analysis can be done by compiling phenotypic records from both families over several generations. This can determine the likelihood that a particular allele is present in either family.

Skill:  Application of knowledge

 

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

Answer:  An inborn error of metabolism is a genetic disease caused by the absence of a particular enzyme necessary to fulfill a biochemical pathway. An example is alkaptonuria, in which an enzyme necessary for homogentisic acid (HA) metabolism is not made. Therefore, people with this disease cannot metabolize HA and it is excreted in their urine.

Skill:  Factual recall

 

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

Answer:  This is because first cousins have many alleles in common, so the chances are greater for recessive alleles to be homozygous in children of first-cousin marriages.

Skill:  Conceptual understanding

 

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

Answer:  They are all marked by a block in the phenylalanine-tyrosine metabolic pathways.

Skill:  Factual recall

 

44) 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?

Answer:  You would grow the strain on a series of media each supplemented with a chemical intermediate in the methionine biosynthetic pathway and observe for growth. The mutant will be able to grow on any medium that contains an intermediate substance in the pathway that comes after the step controlled by its mutant gene. It will also accumulate the intermediate compound used in the step where it is blocked.

Skill:  Analytical reasoning

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

Answer:  There are a number of biochemical steps in melanin biosynthesis from tyrosine. For this reason, albinism can be caused by different enzyme deficiencies at different steps of the pathway. If each of the parents albinism stems from a different enzyme deficiency, they can therefore have a child with normal pigment.

Skill:  Analytical reasoning

 

 

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

Answer:  The cystic fibrosis gene was identified by a combination of genetic and modern molecular biology techniques. It was first localized to chromosome 7, and then molecularly cloned and sequenced. The sequence of the mutant allele was compared with the allele of a normal person to discover a three base-pair deletion in the cystic fibrosis gene. To determine the genes function, its amino acid sequence and three-dimensional structure was deduced. This was compared with a database of protein sequences to determine the genes function as an active transport protein.

Skill:  Factual recall

 

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

Answer:  If they were a carrier, the person, as a heterozygote, would be expected to produce only half the normal enzyme or protein product for the gene in question.

Skill:  Analytical reasoning

 

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

Answer:  Chorionic villus sampling is generally performed up to four weeks earlier than amniocentesis, allowing parents to make an earlier decision regarding potential termination of pregnancies. It is also a faster test that does not require cell culture to do biochemical assays.

Skill:  Factual recall

 

49) Explain the difference between the one-geneone-enzyme hypothesis and the one-geneone-polypeptide hypothesis.

Answer:  A relationship is found between a mutation in a single gene and the loss of production of a single enzyme in a metabolic pathway. However, more than one gene may control each step in a pathway because some enzymes (and some non-enzyme proteins such as hemoglobin) consist of two or more polypeptide chains, each of which is coded for by a different gene. Thus, it is more accurate to use the phrase one-geneone-polypeptide.

Skill:  Conceptual understanding

50) 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?

Answer:  Since the woman has the disease, she must be homozygous recessive for the defective autosomal gene. If her husband is not a carrier, all their children will be heterozygous carriers of the disease. However, since the man and woman are closely related, there is a high probability that the man is a carrier of the PKU gene. If he is a carrier, there is a 50% chance that any of their children will have the disease. You would perform a detailed pedigree analysis for the couple to better determine the probability that the husband carries the recessive allele.

Skill:  Problem-solving

iGenetics: A Molecular Approach, 3e (Russell/Bose)

Chapter 12   Chromosomal Basis of Inheritance

 

MATCHING

 

Please select the best match for each term.

 

  1. A) Mammalian female
  2. B) Polyploidy
  3. C) Turner syndrome
  4. D) Klinefelter syndrome
  5. E) Aneuploidy

 

1) XXY

Skill:  Factual recall

 

2) XO

Skill:  Factual recall

 

3) XX

Skill:  Factual recall

 

4) 2N+1

Skill:  Factual recall

 

5) 3N

Skill:  Factual recall

 

Answers: 1) D 2) C 3) A 4) E 5) B

 

 

MULTIPLE CHOICE

 

6) A person with an XO genotype for the sex chromosomes would be phenotypically

  1. A) male.
  2. B) female.
  3. C) intersex (both male and female).
  4. D) male or female with equal probability.
  5. E) neither male nor female.

Answer:  B

Skill:  Factual recall

 

7) Cells obtained from a Triplo-X woman would contain ________ Barr bodies.

  1. A) 0
  2. B) 1
  3. C) 2
  4. D) 3
  5. E) 4

Answer:  C

Skill:  Application of knowledge

 

8) In human males, genes on the X chromosome are

  1. A) homozygous.
  2. B) heterozygous.
  3. C) homogametic.
  4. D) heterogametic.
  5. E) hemizygous.

Answer:  E

Skill:  Factual recall

9) In butterflies, males are the ________ sex.

  1. A) homozygous
  2. B) heterozygous
  3. C) homogametic
  4. D) heterogametic
  5. E) hemizygous

Answer:  C

Skill:  Factual recall

 

10) The key gene in mammalian sex determination is

  1. A) the testis-determining factor gene.
  2. B) the Y-factor gene.
  3. C) the holandric factor gene.
  4. D) the X-inactivation center.
  5. E) the lyonization gene.

Answer:  A

Skill:  Factual recall

 

 

11) A litter produced by a calico cat is not expected to include

  1. A) solid-colored female kittens.
  2. B) calico female kittens.
  3. C) solid-colored male kittens.
  4. D) calico male kittens.
  5. E) Any of these

Answer:  D

Skill:  Application of knowledge

 

12) A human male who undergoes a sex-change operation will be chromosomally

  1. A) XX.
  2. B) XY.
  3. C) XXY.
  4. D) XYY.
  5. E) YYY.

Answer:  B

Skill:  Factual recall

 

13) The chromosome theory of inheritance states that

  1. A) genes are located on chromosomes.
  2. B) chromosomes replicate before cell division.
  3. C) alleles of a gene segregate during cell division.
  4. D) chromosomes consist of DNA.
  5. E) different chromosomes assort independently of one another.

Answer:  A

Skill:  Factual recall

14) The spindle fibers attach to the centromere via a protein complex called

  1. A) tubulins.
  2. B) microtubules.
  3. C) chromatid.
  4. D) kinetochore.
  5. E) chiasma.

Answer:  D

Skill:  Factual recall

 

15) Plants that produce separate male and female flowers are said to be

  1. A) hermaphroditic.
  2. B) heterosexual.
  3. C) monoecious.
  4. D) dioecious.
  5. E) homosexual.

Answer:  D

Skill:  Factual recall

 

 

16) In an organism with 16 chromosomes per cell, how many DNA molecules are present in a cell undergoing anaphase of mitosis?

  1. A) 8
  2. B) 16
  3. C) 24
  4. D) 32
  5. E) 64

Answer:  D

Skill:  Application of knowledge

 

17) Synaptonemal complex forms during

  1. A) leptonema.
  2. B) zygonema.
  3. C) pachynema.
  4. D) diplonema.
  5. E) diakinesis.

Answer:  B

Skill:  Factual recall

 

18) Phenotypically, a female (XX) mouse embryo that was transformed with a small piece of a Y chromosome bearing the SRY gene would develop as

  1. A) a male.
  2. B) a female.
  3. C) an intersex individual.
  4. D) a male initially, then revert to female after birth.
  5. E) a female initially, then revert to male after birth.

Answer:  A

Skill:  Factual recall

19) Which of the following is an example of genetic mosaicism?

  1. A) Calico coat color in cats
  2. B) Albinism in mice
  3. C) Male pattern baldness in humans
  4. D) Red-green color blindness in humans
  5. E) White eyes in Drosophila

Answer:  A

Skill:  Factual recall

 

20) Individuals with Turner syndrome are

  1. A) euploid.
  2. B) aneuploid.
  3. C) polyploid.
  4. D) haploid.
  5. E) monoploid.

Answer:  B

Skill:  Factual recall

 

 

21) Which of the following organisms has a ZZ-ZW method of sex determination?

  1. A) House mice
  2. B) Monarch butterflies
  3. C) Fruit flies
  4. D) Humans
  5. E) Worms

Answer:  B

Skill:  Factual recall

 

22) The largest human autosome is chromosome ________ and the smallest is chromosome ________.

  1. A) 1, 22
  2. B) 1, 21
  3. C) 1, Y
  4. D) X, 22
  5. E) None of these

Answer:  B

Skill:  Factual recall

 

23) Chromosomes with only one arm are known as

  1. A) metacentric.
  2. B) submetacentric.
  3. C) acrocentric.
  4. D) telocentric.
  5. E) acentric.

Answer:  D

Skill:  Factual recall

24) Red-green color blindness in humans is an X-linked recessive trait. What will the progeny ratios be if a carrier female is mated with a normal male?

  1. A) All the sons will be color blind; all the daughters will be normal.
  2. B) All the sons and half the daughters will be color blind.
  3. C) Half the sons will be color blind; all the daughters will be carriers.
  4. D) Half the sons will be color blind; half the daughters will be carriers.
  5. E) All the sons and all the daughters will be normal.

Answer:  D

Skill:  Problem-solving

 

25) Which of the following statements is not true?

  1. A) Many plants exhibit alternation between haploid and diploid stages.
  2. B) Chromosome number is generally constant within groups of organisms with common ancestry.
  3. C) The Y-bearing sex is known as the heterogametic sex.
  4. D) Sex determination is chromosomal in some organisms and genic in others.
  5. E) The sex chromosome systems of birds and mammals are likely to have evolved independently.

Answer:  B

Skill:  Factual recall

 

TRUE/FALSE

 

26) A person with two X chromosomes is the homogametic sex.

Answer:  TRUE

Skill:  Factual recall

 

27) A woman who is heterozygous for the hemophilia allele has a 100% chance of having an affected son.

Answer:  FALSE

Explanation:  The woman has one affected and one unaffected allele and will donate only one of these, with equal probability, to each of her sons.

Skill:  Factual recall

 

28) Half a womans somatic cells express her paternal X chromosome and half express her maternal X chromosome.

Answer:  FALSE

Explanation:  X-inactivation is random, so the maternal and paternal copies of her X chromosomes will not be inactivated with equal frequency.

Skill:  Factual recall

 

29) Synapsis usually forms between nonsister chromatids.

Answer:  TRUE

Skill:  Conceptual understanding

 

30) X-linked or sex-linked traits are expressed in males but not in females.

Answer:  FALSE

Explanation:  Such traits are expressed most commonly in males due to their hemizygosity, but can be expressed in females homozygous for the X-linked alleles.

Skill:  Factual recall

31) Barr bodies are inactivated X chromosomes.

Answer:  TRUE

Skill:  Factual recall

 

32) In flowering plants, gametes are produced mitotically from spores.

Answer:  TRUE

Skill:  Factual recall

 

33) The centrioles are highly conserved chromosome regions that interact with spindle fibers during cell division.

Answer:  FALSE

Explanation:  The chromosome region that interacts with spindle fibers is the centromere.

Skill:  Factual recall

 

34) Some cells may exit the cell cycle and enter a nondividing G0 state.

Answer:  TRUE

Skill:  Factual recall

 

35) Nondisjunction is the failure of sex chromosomes to separate during gamete formation.

Answer:  FALSE

Explanation:  Nondisjunction is the failure of chromosomes to separate. This can involve either autosomes or sex chromosomes, and may occur either during mitosis or meiosis.

Skill:  Factual recall

 

SHORT ANSWER

 

36) Describe two dosage compensation mechanisms found in animals.

Answer:  X-inactivation in females, in which one X chromosome is silenced, and X-hyperactivation in males, in which genes on the X chromosome have increased expression.

Skill:  Factual recall

 

37) X-linked traits are more likely to be expressed in males. Why? Under what circumstances are they expressed in females?

Answer:  Males are hemizygous, with only one X chromosome; therefore, any genes on that chromosome are expressed, regardless of whether they are dominant or recessive. Females must be homozygous for a recessive X-linked allele to be expressed.

Skill:  Conceptual understanding

 

38) What is the connection between the work of Mary Lyon and Murray Barr?

Answer:  Mary Lyon put forth the theory of X-inactivation, now called lyonization. Murray Barr was the first to describe Barr bodies, which we now know are inactivated X chromosomes.

Skill:  Factual recall

 

39) Why will a human embryo develop as a male in the presence of a Y chromosome, regardless of the number of X chromosomes present?

Answer:  Sex is determined by genes located on the Y chromosome that lead to the development of masculine traits. Even one Y copy, regardless of the number of X chromosomes, is thus sufficient to initiate male development.

Skill:  Conceptual understanding

40) Nondisjunction can lead to two forms of aneuploidy. What are they, and how do they occur?

Answer:  The two most common aneuploid conditions are N + 1 and N 1 (one extra and one missing chromosome, respectively). The N + 1 condition arises when two chromatids of a given chromosome fail to separate during meiosis, giving the resulting gamete an additional copy of that chromosome. Likewise, the N 1 condition is found in the gamete missing a chromatid that stayed paired with its sister.

Skill:  Conceptual understanding

 

41) A woman who is color blind, a sex-linked trait, has several children with a man who has normal vision. What are the possible phenotypes of their children with respect to this trait?

Answer:  All their daughters will have normal vision, while all their sons will be color blind.

Skill:  Problem-solving

 

 

42) What are the differences between metaphase I and metaphase II of meiosis?

Answer:  Metaphase I of meiosis has the same number of chromosomes as the original cells, while metaphase II of meiosis has half the number of chromosomes. In metaphase I, the homologous chromosomes are arranged in pairs at the metaphase plate, whereas in metaphase II there are no homologs, and therefore, individual chromosomes are arranged separately at the metaphase plate.

Skill:  Factual recall

 

43) The chromosome theory of inheritance sought to explain Mendelian patterns in terms of chromosome movement. Can you think of an experimental approach to test for the Mendelian principle of segregation using chromosomes?

Answer:  If replicating chromosomes could be chemically marked, permitting identification of each daughter chromatid, the movement of each could then be tracked. Radioisotopes are commonly used in such labeling experiments.

Skill:  Analytical reasoning

 

44) How did chromosomes get their name?

Answer:  The term, literally meaning colored bodies, was coined in the late nineteenth century at a time when these nuclear structures could be only indistinctly viewed through a microscope with staining.

Skill:  Conceptual understanding

 

45) Describe a situation in which two aneuploid gametes would yield a euploid zygote.

Answer:  The aneuploidy of the gametes must be such that the same chromosomes are affected in each, one with an extra copy of the chromosome and the other only deficient in that same chromosome. Fusion of these two gametes would restore euploidy.

Skill:  Analytical reasoning

 

46) You are a breeder of animals with an X-linked coat-color gene, one allele of which gives black fur and another of which gives white fur. If you cross a black-colored female with a white-colored male, what would their male and female offspring look like?

Answer:  Their male offspring would be all black, while their female offspring would be mottled, owing to X-inactivation:

XbXb  XwY            males: XbY (black)

females: XbXw (some fur patches black, some white)

Skill:  Problem-solving

47) Describe Calvin Bridgess classic study of nondisjunction of sex chromosomes, which provided support for the chromosome theory of inheritance.

Answer:  Bridges performed crosses with fruit flies, tracking the sex-linked eye-color trait. Red-eyed males were crossed with white-eyed females, yielding mostly white-eyed male offspring and red-eyed female offspring. A handful of anomalous individuals proved informative: about 1/2,000 offspring were white-eyed females or red-eyed males. Karyotypic study of these anomalous individuals revealed they had suffered nondisjunction of the sex chromosomes.

Skill:  Problem-solving

 

 

48) Closely related species, like chimpanzees and humans, often differ in chromosome number by only one or two chromosomes, suggesting that chromosomes can experience fission and fusion over evolutionary time. Can you think of a way to test this?

Answer:  Generate a karyotype for the species of interest and stain the chromosomes to obtain banding patterns. Compare the banding patterns of chromosomes that you speculate may be the product of fission or fusionbanding patterns are highly conservedand you should be able to match up the chromosomes from one species with those of another.

Skill:  Analytical reasoning

 

49) Drosophila fruit flies, like mammals, have an X-Y sex-determination system. The insect differs from the mammalian system in an important respect, however. What is it?

Answer:  While Drosophila has X-Y sex determination, where XX individuals are female and XY individuals are male, studies have shown that sex determination is based on the ratio of X chromosomes to autosomes rather than on Y-linked genes. Thus, XO Drosophila develop as males and XXY Drosophila develop as femalesthe same X : autosome ratio as XY and XX individuals.

Skill:  Factual recall

 

50) What pattern of expression is expected for an X-linked dominant trait like hereditary enamel hypoplasia?

Answer:  An affected father will have affected daughters and no affected sons; an affected mother will have a 50% chance of having an affected son and a 50% chance of having an affected daughter (assuming the mother is heterozygous).

Skill:  Problem-solving

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