Fundamental Molecular Biology, 2nd Edition Instructor Test Bank
Lizabeth A. Allison

Chapter 1 The Beginnings of Molecular Biology

Multiple Choice

1) In 1869 Friedrich Miescher isolated a substance called “nuclein” from pus from soiled 
bandages that was a(n)
A. acidic, phosphorus-rich substance
B. basic, phosphorus-rich substance
C. amino acid-rich substance
D. phospholipid-rich substance
Answer: A

2) The basic principles of genetics attributed to Gregor Johann Mendel are:
A. the laws of segregation and independent assortment
B. the Punnett square
C. the concept of dominant and recessive traits
D. A and C
E.  A, B, and C
Answer: D

3)	The Augustinian monk, Gregor Johann Mendel, crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F2 generation. The results were as follows: 6018 yellow and 2002 green (8020 total). The allele for green seeds has what relationship to the allele for yellow seeds? 
A.	semidominant
B.	incompletely dominant
C.	recessive
D.	dominant
Answer: C

4)	Why is the allele for wrinkled seed shape in garden peas considered recessive?
A.	The wrinkled allele is a rare mutant that is less common than the dominant allele. 
B.	The trait associated with the allele is not expressed in heterozygotes.
C.	Individuals with the allele have overall lower fitness than that of individuals with the dominant allele.
D.	 The wrinkled allele  “recedes” in the F2 generation when homozygous parents are crossed.
Answer: B

5) 	In 1928 Frederick Griffith discovered that Streptococcus pneumonia caused pneumonia in mice. In his experiments, mice were injected with different strains of treated and untreated bacteria. Which of the following is not likely to have occurred in the series of experiments by Griffith?
A.	Mice injected with living S (pathogenic) strain die.
B.	Mice injected with living R (nonpathogenic) strain live.
C.	Mice injected with living R plus heat-killed S die.
D.	Mice injected with living S plus heat-killed R live. 
Answer: D

6)	In 1928, Frederick Griffith injected living S (smooth) Streptococcus pneumonia into mice, and the mice died. When he injected living R (rough) Streptococcus pneumonia into mice, the mice lived. When he injected heat-killed S bacteria into mice, the mice lived. What was the result when he mixed heat-killed S bacteria with live R bacteria and injected this mixture into mice?
A.	The mice died, and living bacteria that appeared smooth could be isolated from the dead mice.
B.	The mice lived, and living bacteria that appeared smooth could be isolated from the living mice.
C.	The mice died, indicating that the heat-killed S bacteria came back to life. 
D.	The mice lived and neither smooth nor rough-appearing bacteria could be isolated from the living mice.
Answer:  A

7) 	In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty used an in vitro agglutination assay to demonstrate that purified DNA was sufficient to cause transformation of cells, and that the transforming factor could be destroyed by 
A. ribonucleases but not by deoxyribonuclease or protease enzymes.
B. proteases but not by deoxyribonuclease or ribonuclease enzymes.
C. deoxyribonucleases but not by protease or ribonuclease enzymes. 
D. both deoxyribonucleases and proteases but not by ribonuclease enzymes.
Answer: C

A     B     C     D
   enzyme a           enzyme b           enzyme c

8)	According to Beadle and Tatum’s one-gene, one-enzyme hypothesis, how many different genes are apparently operating in the pathway shown above? 
A.	It cannot be determined from the pathway.
B.	1
C.	2
D.	3
Answer: D

9)	Beadle and Tatum’s “one gene – one enzyme” hypothesis was later revised to the 
A.	one gene – one polypeptide hypothesis.
B.	one gene – one protein hypothesis.
C.  one gene – one DNA molecule hypothesis.
D.	one gene – one enzyme, one lipid, one RNA molecule, or one carbohydrate hypothesis. 
Answer: A

10) In the 1950s, Hershey and Chase conducted a now famous experiment to determine whether DNA or protein carried the hereditary information in bacteriophage T2. What method did they used to selectively label the DNA and protein components of bacteriophage T2?
A.	35S to label the DNA and 32P to label the protein
B.	35S to label the protein and 32P to label the DNA
C.  35P to label the protein and 32S to label the DNA
D.	none of the above
Answer: B

11)	The classic experiment performed by Alfred Hershey and Martha Chase revealed:
A.	RNA was not the hereditary material.
B.	Microbes could exchange genetic information.	
C.	In a bacteriophage infection, protein was transferred into the infected bacterial cell.
D.	In a bacteriophage infection, DNA was transferred into the infected bacterial cell.
Answer: D

12) In 1953, James Watson and Francis Crick proposed 
A. the tetranucleotide structure of DNA.
B. the one gene – one enzyme hypothesis.
C. the double helix as a model for the structure of DNA.
D. that Griffith’s transforming principle was DNA.
Answer: C

13) The primary principle of the “neutral” theory of natural selection is that 
A.  evolution is primarily driven by purifying selection against deleterious mutations.
B.  advantageous and deleterious mutations play an equal role in evolution.
C.  genetic drift by random allele fixation plays a dominant role in evolution.
D.  it is impossible to deduce whether observed allele frequencies are caused by positive or negative selection.  
Answer: C

14) Neo-Darwinism did not recognize a significant role of _________________ variation in evolution.
A.  advantageous
B.  deleterious
C.  adaptive
D.  neutral 
Answer: D

15) Which of the following theories suggests that mutations create a pool of genetic diversity that may undergo selection at a later time when conditions change?
A.  Darwinism 
B.  Neo-Darwinism
C.  Neutral Theory
D.  Nearly Neutral Theory
Answer: D

16) Darwin’s original theory of evolution recognized ________________ variations.
A. advantageous, deleterious, and neutral
B. advantageous, deleterious, and dominant
C. dominant, recessive, and advantageous
D. neutral, dominant, and recessive
Answer: A

Short answer/analytical

17) Define the terms “in vivo” and “in vitro.”
Answer: Section 1.2, p. 6

18) The discovery by Avery, MacLeod, and McCarty that Griffith’s transforming principle was DNA came as a surprise to scientists at the time. Provide an explanation for why their finding was unexpected.
Answer: Section 1.2, p. p.8

19) Explain how technological advances allowed Alfred Hershey and Martha Chase to carry out their classic experiment in 1952. 
Answer: Section 1.2, p. 11

20) Discuss scientific findings at the time that provided the necessary context for the proposed structure of DNA by Watson and Crick in 1953.
Answer: Section 1.2, p. 11-12

21) Sodium hydroxide denatures both proteins and nucleic acids, while phenol denatures proteins but not nucleic acids. In the transformation experiments performed by Griffith with Streptococcus pnemoniae, what result would be expected if an extract of S-strain bacteria was treated with phenol? What would be expected if it was treated with sodium hydroxide?

Answer: If an extract of S-strain bacteria was treated with phenol and then injected into mice along with live R-strain cells, one would expect the mice to die. Phenol would denature the proteins but not the nucleic acids in the bacterial extract. The S-strain bacterial DNA would be able to transform the R-strain bacteria. If the extract of S-strain bacteria was treated with sodium hydroxide and then injected into mice along with live R-strain cells, one would expect the mice to remain healthy. The extract would not promote transformation, since the DNA would be denatured.

22) When Hershey and Chase infected bacterial cells that had been grown in the presence of radioactive phosphorus with bacteriophage T2, both the phage RNA and DNA must also have incorporated the labeled phosphorus and yet the experimental results were not affected. Why not?

Answer: Even if both the phage RNA and DNA incorporated the labeled phosphorus, the experimental results would not be affected because only the phage DNA is packaged in the progeny particles that were isolated from the lysed bacteria. Either way, the experiment still demonstrated that the protein coat did not enter the host bacterium and therefore could not be providing the genetic information.

23) Four independent methionine auxotrophs of Neurospora were studied to determine which related compounds might substitute for their methionine requirement. In the table below “+” indicates growth on minimal medium supplemented with the indicated compound, and “-” indicates no growth.
 
Mutant strain	Nothing added: (minimal medium)	O-acetyl 
homoserine	Methionine	Homocysteine	Cystathione	
Wild-type	+	+	+	+	+	
Mutant A	-	+	+	+	+	
Mutant B	-	-	+	+	+	
Mutant C	-	-	+	+	-	
Mutant D	-	-	+	-	-	

Based on the results, give the order of these four compounds in the biosynthetic pathway of methionine.

Answer: The order of the four compounds in the biosynthetic pathway of methionine would be: O-acetyl homoserine   cystathione  homocysteine  methionine. 
Mutant B can grow on medium supplemented with both cystathione and homocysteine, but not when supplemented with O-acetyl homoserine alone, indicating that the block in the pathway must occur after homoserine, but before cystathione and homocysteine. Mutant C can grow on medium supplemented with homocysteine, but not with cystathione, indicating that the block in the pathway occurs after cystathione but before homocysteine. From this, the order of these four compounds can be deduced.

24) Explain how Tomoko Ohta’s “nearly neutral” theory of molecular evolution reconciled the differences between neutral evolutionary theory and selection evolutionary theory.
Answer: Section 1.5, p. 14-15