Choose The Correct Option For The Following Biology Of Life Quiz

1. For a couple of decades, biologists knew the nucleus contained DNA and proteins. The prevailing opinion was that the genetic material was proteins, and not DNA. The reason for this belief was that proteins are more complex than DNA. What was the basis of this thinking?

A) Proteins have a greatervariety of three-dimensional forms than does DNA

C) Proteins are made of 40 amino acids and DNA is made of four nucleotides

D) Some viruses only transmit proteins

B) Proteins have two different levels of structural organization; DNA has four

The correct answer is A) Proteins have a greater variety of three-dimensional forms than does DNA. Proteins can fold into a wide range of complex three-dimensional shapes while DNA has a more limited structural variety.

Explanation

The correct answer is A) Proteins have a greater variety of three-dimensional forms than does DNA. Proteins can fold into a wide range of complex three-dimensional shapes while DNA has a more limited structural variety.

2. In his transformation experiments, what did Griffith observe?

B) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.

Mutant mice were resistant to bacterial infections.

Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.

In Griffith's experiments, he observed that the transformation of living nonpathogenic cells into pathogenic cells occurred when a heat-killed pathogenic strain was mixed with the living nonpathogenic strain. This discovery led to the concept of genetic transformation.

Explanation

In Griffith's experiments, he observed that the transformation of living nonpathogenic cells into pathogenic cells occurred when a heat-killed pathogenic strain was mixed with the living nonpathogenic strain. This discovery led to the concept of genetic transformation.

3. What does transformation involve in bacteria?

C) the infection of cells by a phage DNA molecule

A) the creation of a strand of DNA from an RNA molecule

B) the creation of a strand of RNA from a DNA molecule

E) assimilation of external DNA into a cell

Transformation in bacteria refers to the process of taking up external DNA from the environment and incorporating it into the bacterial cell's genome. This process allows bacteria to acquire new genetic material and potentially new traits.

Explanation

Transformation in bacteria refers to the process of taking up external DNA from the environment and incorporating it into the bacterial cell's genome. This process allows bacteria to acquire new genetic material and potentially new traits.

4. The following scientists made significant contributions to our understanding of the structure and function of DNA. Place the scientists' names in the correct chronological order, starting with the first scientist(s) to make a contribution.

D) IV, V, II, I, III

B) II, I, III, V,IV

A) V, III, I, II, IV

C) III, II, V, I, IV

The correct chronological order of the scientists in terms of their contributions to the structure and function of DNA is Griffith, followed by Avery, McCarty, and MacLeod, then Hershey and Chase, Watson and Crick, and finally Meselson and Stahl.

Explanation

The correct chronological order of the scientists in terms of their contributions to the structure and function of DNA is Griffith, followed by Avery, McCarty, and MacLeod, then Hershey and Chase, Watson and Crick, and finally Meselson and Stahl.

5. After mixing a heat-killed, phosphorescent strain of bacteria with a living non-phosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait?

Protein passed from the heat-killed strain to the living strain

DNA passed from the heat-killed strain to the living strain

D) Descendants of the living cells are also phosphorescent.

The phosphorescence in the living strain is especially bright

The best evidence that the ability to fluoresce is a heritable trait would be if descendants of the living cells are also phosphorescent. This would indicate that the trait is passed down from generation to generation genetically.

Explanation

The best evidence that the ability to fluoresce is a heritable trait would be if descendants of the living cells are also phosphorescent. This would indicate that the trait is passed down from generation to generation genetically.

6. In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

E) RNA includes ribose, while DNA includes deoxyribose sugars.

C) DNA contains nitrogen, whereas protein does not.

A) DNA contains sulfur, whereas protein does not.

B) DNA contains phosphorus, but protein does not.

Hershey and Chase's experiment involved labeling viral DNA with radioactive phosphorus, which allowed them to track the viral DNA through the infection process. The fact that DNA contains phosphorus but protein does not helped them determine that DNA, not protein, is the genetic material.

Explanation

Hershey and Chase's experiment involved labeling viral DNA with radioactive phosphorus, which allowed them to track the viral DNA through the infection process. The fact that DNA contains phosphorus but protein does not helped them determine that DNA, not protein, is the genetic material.

7. For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

B) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.

C) Avery et al. have already concluded that this experiment showed inconclusive results.

D) Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.

A) There is no radioactive isotope of nitrogen.

E) Amino acids (and thus proteins) also have nitrogen atoms;thus, the radioactivity would not distinguish between DNA and proteins.

Labeling the nitrogen in DNA would not be a suitable method because amino acids and proteins also contain nitrogen, which would produce the same signal when radioactively labeled, making it impossible to distinguish between DNA and proteins.

Explanation

Labeling the nitrogen in DNA would not be a suitable method because amino acids and proteins also contain nitrogen, which would produce the same signal when radioactively labeled, making it impossible to distinguish between DNA and proteins.

8. Which of the following investigators was/were responsible for the following discovery? Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA.

D) Erwin Chargaff

C) Oswald Avery, Maclyn McCarty, and Colin MacLeod

A) Frederick Griffith

B) Alfred Hershey and Martha Chase

Oswald Avery, Maclyn McCarty, and Colin MacLeod were responsible for the discovery that DNA is the transforming agent. They conducted experiments that showed that DNA was the substance responsible for genetic transformation.

Explanation

Oswald Avery, Maclyn McCarty, and Colin MacLeod were responsible for the discovery that DNA is the transforming agent. They conducted experiments that showed that DNA was the substance responsible for genetic transformation.

9. Which of the following investigators was/were responsible for the following discovery? Phage with labeled proteins or DNA was allowed to infect bacteria. It was shown that the DNA, but not the protein, entered the bacterial cells, and was therefore concluded to be the genetic material.

B) Alfred Hershey and Martha Chase

A) Frederick Griffith

E) Matthew Meselson and Franklin Stahl

C) Oswald Avery, Maclyn McCarty, and Colin MacLeod

Alfred Hershey and Martha Chase conducted the famous Hershey-Chase experiment in 1952, which provided solid evidence that DNA, rather than proteins, transmitted genetic information. Their experiment involved the use of bacteriophages and radioactively labeled DNA and proteins to track the entry of genetic material into bacterial cells.

Explanation

Alfred Hershey and Martha Chase conducted the famous Hershey-Chase experiment in 1952, which provided solid evidence that DNA, rather than proteins, transmitted genetic information. Their experiment involved the use of bacteriophages and radioactively labeled DNA and proteins to track the entry of genetic material into bacterial cells.

10. Which of the following investigators was/were responsible for the following discovery: In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine?

D) Erwin Chargaff

C) Maurice Wilkins

B) Rosalind Franklin

A) James Watson and Francis Crick

Erwin Chargaff was a biochemist who made important contributions to the understanding of DNA composition. Chargaff's rules, which state that in DNA the amount of adenine equals thymine and the amount of guanine equals cytosine, played a crucial role in the discovery of the structure of DNA.

Explanation

Erwin Chargaff was a biochemist who made important contributions to the understanding of DNA composition. Chargaff's rules, which state that in DNA the amount of adenine equals thymine and the amount of guanine equals cytosine, played a crucial role in the discovery of the structure of DNA.

11. When T2 phages infect bacteria and make more viruses in the presence of radioactive sulfur, what is the result?

B) The viral proteins will be radioactive.

D) both A and B

A) The viral DNA will be radioactive.

C) The bacterial DNA will be radioactive.

When T2 phages infect bacteria in the presence of radioactive sulfur, the sulfur is incorporated into the viral proteins during replication, making the viral proteins radioactive. This is due to the fact that proteins are composed of amino acids, some of which may contain sulfur atoms. The viral DNA does not typically incorporate sulfur, so it does not become radioactive. Similarly, the bacterial DNA is not affected by the presence of radioactive sulfur.

Explanation

When T2 phages infect bacteria in the presence of radioactive sulfur, the sulfur is incorporated into the viral proteins during replication, making the viral proteins radioactive. This is due to the fact that proteins are composed of amino acids, some of which may contain sulfur atoms. The viral DNA does not typically incorporate sulfur, so it does not become radioactive. Similarly, the bacterial DNA is not affected by the presence of radioactive sulfur.

12. Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

C) 31

B) 24

A) 12

D) 38

To find the approximate percentage of thymine, we know that in DNA, Cytosine (C) pairs with Guanine (G) and Thymine (T) pairs with Adenine (A). Since Cytosine makes up 38%, Thymine will also be 12% as the base pairs are equal in a DNA molecule, each comprising 50% and since both Guanine and Adenine make up the remaining 62%, Thymine (T) will also be 12%.

Explanation

To find the approximate percentage of thymine, we know that in DNA, Cytosine (C) pairs with Guanine (G) and Thymine (T) pairs with Adenine (A). Since Cytosine makes up 38%, Thymine will also be 12% as the base pairs are equal in a DNA molecule, each comprising 50% and since both Guanine and Adenine make up the remaining 62%, Thymine (T) will also be 12%.

13. Chargaff's analysis of the relative base composition of DNA was significant because he was able to show that

D) the amount of ribose is always equivalent to deoxyribose.

A) the relative proportion of each of the four bases differs within individuals of a species.

C) the amount of A isalways equivalent to T, and C to G.

B) the human genome is more complex than that of other species.

Chargaff's analysis of DNA base composition established the principle that the amount of adenine (A) is equal to thymine (T) and the amount of cytosine (C) is equal to guanine (G) in the DNA of a species.

Explanation

Chargaff's analysis of DNA base composition established the principle that the amount of adenine (A) is equal to thymine (T) and the amount of cytosine (C) is equal to guanine (G) in the DNA of a species.

14. Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?

B) the rate of replication

C) the sequence of nucleotides

D) the bond angles of the subunits

A) the diameter of the helix

X-ray diffraction photographs of crystallized DNA provide information about the physical structure of the DNA molecule, such as the spacing between the bases which allows for determination of the diameter of the DNA helix. However, factors like the rate of replication, specific nucleotide sequences, and bond angles are not directly determined from X-ray diffraction photographs.

Explanation

X-ray diffraction photographs of crystallized DNA provide information about the physical structure of the DNA molecule, such as the spacing between the bases which allows for determination of the diameter of the DNA helix. However, factors like the rate of replication, specific nucleotide sequences, and bond angles are not directly determined from X-ray diffraction photographs.

15. Why does the DNA double helix have a uniform diameter?

D) Nucleotides bind with nucleosides.

A) Purines pair with pyrimidines.

B) C nucleotides pair with A nucleotides.

C) Deoxyribose sugars bind with ribose sugars.

The DNA double helix has a uniform diameter because purines (adenine and guanine) always pair with pyrimidines (thymine and cytosine), ensuring that the structure maintains a constant width.

Explanation

The DNA double helix has a uniform diameter because purines (adenine and guanine) always pair with pyrimidines (thymine and cytosine), ensuring that the structure maintains a constant width.

16. Watson and Crick realized that the DNA molecule could carry a vast amount of hereditary information primarily in which of the following?

C) complementary pairing of bases

D) side groups of nitrogenous bases

A) sequence of bases

B) phosphate-sugar backbones

The hereditary information in DNA is encoded in the specific sequence of nucleotide bases (adenine, thymine, cytosine, and guanine) along the DNA strand. This sequence of bases determines the genetic instructions for an organism, making option A the correct choice.

Explanation

The hereditary information in DNA is encoded in the specific sequence of nucleotide bases (adenine, thymine, cytosine, and guanine) along the DNA strand. This sequence of bases determines the genetic instructions for an organism, making option A the correct choice.

17. Replication in prokaryotes differs from replication in eukaryotes for which of these reasons?

B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many

C) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes.

E) Prokaryotes have telomeres, and eukaryotes do not.

A) The prokaryotic chromosome has histones, whereas eukaryotic chromosomes do not.

In prokaryotes, replication typically begins at a single origin of replication, while in eukaryotes, replication occurs at multiple origins. This is one of the fundamental differences in the mechanisms of DNA replication between prokaryotes and eukaryotes.

Explanation

In prokaryotes, replication typically begins at a single origin of replication, while in eukaryotes, replication occurs at multiple origins. This is one of the fundamental differences in the mechanisms of DNA replication between prokaryotes and eukaryotes.

18. What is meant by the description 'antiparallel' regarding the strands that make up DNA?

A) The twisting nature of DNA creates nonparallel strands.

C) Base pairings create unequal spacing between the two DNA strands.

B) The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

D) One strand is positively charged and the other is negatively charged.

In DNA, the strands are antiparallel because one strand runs in the 5' to 3' direction while the other runs in the opposite 3' to 5' direction. This characteristic is essential for the complementary base pairing that allows DNA replication and transcription to take place effectively.

Explanation

In DNA, the strands are antiparallel because one strand runs in the 5' to 3' direction while the other runs in the opposite 3' to 5' direction. This characteristic is essential for the complementary base pairing that allows DNA replication and transcription to take place effectively.

19. Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

E) DNA in both daughter cells would be radioactive.

B) Neither of the two daughter cells would be radioactive.

D) Radioactive thymine would pair with nonradioactive guanine.

A) One of the daughter cells, but not the other, would have radioactive DNA.

When a cell replicates in the presence of radioactive thymine, the DNA in both daughter cells would be radioactive due to the incorporation of the radioactive base during DNA synthesis.

Explanation

When a cell replicates in the presence of radioactive thymine, the DNA in both daughter cells would be radioactive due to the incorporation of the radioactive base during DNA synthesis.

20. In the late 1950s, Meselson and Stahl grew bacteria in a medium containing 'heavy' nitrogen (15N) and then transferred them to a medium containing 14N. Which of the following results would be expected after one round of DNA replication in the presence of 14N?

C

D

A

B

The correct answer is D because after one round of DNA replication in the presence of 14N, the DNA molecules will consist of one hybrid band (1/2 15N and 1/2 14N), which is represented by result D in the figure.

Explanation

The correct answer is D because after one round of DNA replication in the presence of 14N, the DNA molecules will consist of one hybrid band (1/2 15N and 1/2 14N), which is represented by result D in the figure.

21. A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in Figure 16.1 would you expect if the DNA was replicated in a conservative manner?

C

B

D

A

In conservative replication, the original double-stranded DNA remains intact and two new strands are synthesized. Option B represents conservative replication where one molecule is entirely comprised of the parent DNA, while the other is entirely comprised of the newly synthesized DNA.

Explanation

In conservative replication, the original double-stranded DNA remains intact and two new strands are synthesized. Option B represents conservative replication where one molecule is entirely comprised of the parent DNA, while the other is entirely comprised of the newly synthesized DNA.

22. Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?

D) Replication is not conservative

C) Replication is not semi-conservative.

A) Replication is semi-conservative.

B) Replication is not dispersive.

Meselson and Stahl's experiment with E. coli DNA replication using isotopic labeling demonstrated that DNA replication is not conservative, but rather semi-conservative. This conclusion was based on the observation of DNA hybrid molecules with one heavy strand and one light strand after one round of replication.

Explanation

Meselson and Stahl's experiment with E. coli DNA replication using isotopic labeling demonstrated that DNA replication is not conservative, but rather semi-conservative. This conclusion was based on the observation of DNA hybrid molecules with one heavy strand and one light strand after one round of replication.

23. Which of the following arrangements describe an Okazaki fragment?

B) 3' RNA nucleotides, DNA nucleotides 5'

A) primase, polymerase, ligase

D) DNA polymerase I, DNA polymerase III

C) 5' RNA nucleotides, DNA nucleotides 3'

Okazaki fragments are short, newly synthesized DNA fragments formed on the lagging strand during DNA replication. They are composed of RNA nucleotides on the 5' end and DNA nucleotides on the 3' end, hence option C is correct.

Explanation

Okazaki fragments are short, newly synthesized DNA fragments formed on the lagging strand during DNA replication. They are composed of RNA nucleotides on the 5' end and DNA nucleotides on the 3' end, hence option C is correct.

24. In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?

No proofreading will occur.

The DNA will supercoil.

Replication will occur via RNA polymerase alone.

B) No replication fork will be formed.

The alteration of the helicase due to the dnaB mutation would prevent the formation of the replication fork, leading to a disruption in the replication process.

Explanation

The alteration of the helicase due to the dnaB mutation would prevent the formation of the replication fork, leading to a disruption in the replication process.

25. Which enzyme catalyzes the elongation of a DNA strand in the 5' - 3' direction?

B) DNA ligase

C) DNA polymerase III

A) primase

D) topoisomerase

26. What determines the nucleotide sequence of the newly synthesized strand during DNA replication?

C) the nucleotide sequence of the template strand

B) the relative amounts of the four nucleoside triphosphates in the cell

A) the particular DNA polymerase catalyzing the reaction

D) the primase used in the reaction

The nucleotide sequence of the newly synthesized DNA strand is determined by complementary base pairing with the template strand during replication, where adenine pairs with thymine and guanine pairs with cytosine. The template strand provides the 'instructions' for the correct nucleotide sequence in the newly synthesized strand.

Explanation

The nucleotide sequence of the newly synthesized DNA strand is determined by complementary base pairing with the template strand during replication, where adenine pairs with thymine and guanine pairs with cytosine. The template strand provides the 'instructions' for the correct nucleotide sequence in the newly synthesized strand.

27. Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?

A) The evolution of telomerase enzyme

C) Gaps left at the 5' end of the lagging strand because of the need for a 3' onto which nucleotides can attach

D) Gaps left at the 3' end of the lagging strand because of the need for a primer

B) DNA polymerase that cannot replicate the leading strand template to its 5' end

Eukaryotic telomeres have unique structural features that require specialized mechanisms for replication. The gaps left at the 5' end of the lagging strand due to the 'end replication problem' result in the need for a 3' end onto which nucleotides can attach, leading to the unique replication process of telomeres.

Explanation

Eukaryotic telomeres have unique structural features that require specialized mechanisms for replication. The gaps left at the 5' end of the lagging strand due to the 'end replication problem' result in the need for a 3' end onto which nucleotides can attach, leading to the unique replication process of telomeres.