Deck 4: Nucleic Acids and the Rna World

Question 1

What feature of mononucleotides provides the energy needed for polymerization when nucleic acids are formed?

A)their methyl groups
B)their sugar groups
C)their nitrogenous bases
D)their phosphate groups

Answer 1

D

Question 2

Which of the following best describes DNA's secondary structure?

A)beta-pleated sheet
B)double parallel helical strands
C)turn-loop-turn
D)double antiparallel helical strands

Answer 2

D

Question 3

RNA and proteins combine in cells to form structures called ribosomes.Ribosomes contain the active site for peptide bond formation.Based on their chemical structures,do you think protein or RNA molecules actually form the active site within the ribosome?

A)protein,because RNA cannot catalyze reactions
B)RNA,because proteins cannot catalyze a reaction that involves another protein
C)proteins,because only proteins can catalyze a reaction that involves another protein
D)It could be either,because both molecules have catalytic properties.

Answer 3

D

Question 4

You have a polymer of DNA with 10 adenine bases followed by 10 cytosine bases.If that strand bonded to a strand of 20 thymine bases,how would the double helix shape vary from a typical DNA double helix?

A)The double helix would be longer than normal.
B)The double helix would be shorter than normal.
C)One strand of the double helix would be longer than the other strand.
D)The width of the double helix would vary as you moved down the strand.

Question 5

Nucleic acids have a definite polarity,or directionality.Stated another way,one end of the molecule is different from the other end.How are these ends described?

A)One end has a hydroxyl group on the 2 carbon;the other end has a hydrogen atom on the 2 carbon.
B)One end contains a nitrogenous base;the other end lacks it.
C)One end has an unlinked 3 carbon;the other end has an unlinked 5 carbon.
D)One end has one phosphate group;the other end has two phosphate groups.

Question 6

Which of the following includes all of the pyrimidines found in RNA and/or DNA?

A)cytosine and uracil
B)cytosine and thymine
C)cytosine,uracil,and thymine
D)cytosine,uracil,and guanine

Question 7

What is gel electrophoresis used for?

A)to denature proteins for further analysis
B)to separate macromolecules by size or charge
C)to separate the two helices that make up the DNA double helix
D)to identify the first self-replicating molecule that formed during chemical evolution

Question 8

Compare proteins to nucleic acids.Which of the following is true?

A)Both have primary and secondary structure.
B)Both contain sulfur.
C)Both take on structural roles in the cell.
D)Monomers of both contain phosphorus.

Question 9

What is/are the variable structure(s)of a nucleotide?

A)the phosphate group
B)the sugar
C)the base
D)the sugar and the base

Question 10

Nucleic acids are polymers made up of which of the following monomers?

A)nucleotides
B)sugars
C)amino acids
D)nitrogenous bases

Question 11

Franklin and Wilkins analyzed DNA by bombarding DNA crystals with X-rays.Their analysis yielded two numbers that sparked interest,3.4 nm and 0.34 nm.What is the significance of these numbers?

A)It turned out to be just a coincidence.
B)DNA molecules are 3.4 nm long and 0.34 nm wide.
C)The width of a DNA molecule is 3.4 nm,whereas the width of a nucleotide monomer is 0.34 m.
D)These numbers tell us there are 10 rungs,or steps,on the DNA "ladder" for every turn of the helix.
E)The 10-to-1 ratio signifies that DNA molecules are 10 times longer than they are wide.

Question 12

Why is it that RNA can catalyze reactions but DNA cannot?

A)The sugar of RNA is much more reactive than the sugar of DNA.
B)The bases of RNA are much more reactive than the bases of DNA.
C)The phosphate groups of RNA are much more reactive than the phosphate groups of DNA.
D)The primary structure of RNA is fundamentally different than the primary structure of DNA.

Question 13

When nucleotides polymerize to form a nucleic acid _____.

A)a covalent bond forms between the sugar of one nucleotide and the phosphate of a second
B)a hydrogen bond forms between the sugar of one nucleotide and the phosphate of a second
C)covalent bonds form between the bases of two nucleotides
D)hydrogen bonds form between the bases of two nucleotides

Question 14

What is the difference between a ribonucleotide and a deoxyribonucleotide?

A)Ribonucleotides contain a phosphate group.
B)Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
C)Ribonucleotides contain a sugar with five carbon atoms.
D)Ribonucleotides have a hydrogen atom on the 1 carbon of their sugar subunit.

Question 15

DNA double helices are soluble in water but insoluble in alcohol.How do these physical properties reflect the chemical structure of the molecule?

A)The charged phosphate groups and sugars of DNA "like" to interact with polar water molecules.
B)The purine and pyrimidine bases "like" to interact with polar water molecules.
C)The 5 prime to 3 prime polarity of DNA make it soluble in water but not in alcohol.
D)The charged R-groups of DNA "like" to interact with polar water molecules.

Question 16

In the context of chemical evolution,DNA's structure is interesting because it suggests a possible copying mechanism.What about DNA's structure facilitates copying?

A)It has the same number of purines and pyrimidines.
B)The nitrogenous bases are located on the inside of the double helix.
C)The strands of the double helix are complementary.
D)DNA always goes from 5 to 3.

Question 17

Which of these scientists was not directly involved in the discovery of DNA's structure?

A)James Watson
B)Rosalind Franklin
C)Sidney Altman
D)Francis Crick
E)Maurice Wilkins

Question 18

Which of the following did Watson and Crick already know when they were trying to determine the structure of DNA?

A)The number of purines is always larger than the number of pyrimidines.
B)The number of pyrimidines is always larger than the number of purines.
C)The number of cytosines is always the same as the number of adenines.
D)The number of guanines is always the same as the number of thymines.
E)The number of purines is always the same as the number of pyrimidines.

Question 19

Some viruses consist only of a protein coat surrounding a nucleic acid core.If you wanted to radioactively label the nucleic acids separately from the protein,you would use _____.

A)radioactive sulfur
B)radioactive carbon
C)radioactive nitrogen
D)radioactive phosphorus

Question 20

Which of the terms or phrases below apply to both DNA and RNA?

A)an information-containing structure
B)shows primary,secondary,tertiary,and quaternary structure
C)is the most common type of organic molecule to catalyze chemical reactions in cells
D)All of the above apply.

Question 21

Although DNA is the main hereditary material in all life-forms,it lacks one important characteristic of being a candidate for the first life-form.Why have researchers rejected the idea that DNA was found in the first life-form?

A)It does not function as a catalyst.
B)It is not stable enough to have withstood early Earth's harsh atmosphere.
C)Because it has only four different bases,it does not carry enough information;therefore,it cannot adapt and evolve.
D)The type of sugar found in DNA is much too complicated to have been present early in Earth's history.

Question 22

Use the following information when answering the corresponding question(s).
Shu-ichi Nakano reported in Science in February 2000 that "The RNA enzyme (ribozyme)from hepatitis delta virus catalyzes self-cleavage of a ...[chemical] ...bond." This reaction is inherently slow due to the formation of an unfavorable negative charge on the ribozyme.The author goes on to show that this self-cleavage is made faster by joining it with an acid-base reaction that neutralizes the negative charge.Nakano's model describes a positively charged cytosine base on the ribozyme acting as the acid,and magnesium hydroxide acting as the base.Specifically,the cytosine donates its proton (H⁺)to neutralize the unstable negative charge that would have formed on the ribozyme.
Refer to Nakano's quote from Science.If the cytosine is positively charged (+)before self-cleavage,what would its charge be after self-cleavage?

A)+ (positive)
B)- (negative)
C)0 (neutral)
D)no way to predict

Question 23

Which one of the following is not a way that RNA is seen as intermediate between DNA and proteins?

A)RNA contains genetic information like DNA,but is not as stable.
B)RNA can catalyze reactions,but not as well as can proteins.
C)RNA is composed of nucleotides,but forms tertiary and quaternary structures like a protein.
D)RNA has 5 and 3 termini like DNA,but it also has amino and carboxy termini like protein.

Question 24

Which of the following is a difference between RNA and DNA?

A)One is typically single stranded and the other is typically triple stranded.
B)One contains uracil and the other does not.
C)One contains ribose sugar and the other contains a deoxyribose sugar.
D)One is made from nucleotide monomers and the other one is not.

Question 25

Use the following information when answering the corresponding question(s).
Shu-ichi Nakano reported in Science in February 2000 that "The RNA enzyme (ribozyme)from hepatitis delta virus catalyzes self-cleavage of a ...[chemical] ...bond." This reaction is inherently slow due to the formation of an unfavorable negative charge on the ribozyme.The author goes on to show that this self-cleavage is made faster by joining it with an acid-base reaction that neutralizes the negative charge.Nakano's model describes a positively charged cytosine base on the ribozyme acting as the acid,and magnesium hydroxide acting as the base.Specifically,the cytosine donates its proton (H⁺)to neutralize the unstable negative charge that would have formed on the ribozyme.
Which of the following chemical bonds do you think Nakano is referring to in his quote?

A)peptide
B)glycosidic
C)phosphodiester
D)ionic

Question 26

Use the following information when answering the corresponding question(s).
Shu-ichi Nakano reported in Science in February 2000 that "The RNA enzyme (ribozyme)from hepatitis delta virus catalyzes self-cleavage of a ...[chemical] ...bond." This reaction is inherently slow due to the formation of an unfavorable negative charge on the ribozyme.The author goes on to show that this self-cleavage is made faster by joining it with an acid-base reaction that neutralizes the negative charge.Nakano's model describes a positively charged cytosine base on the ribozyme acting as the acid,and magnesium hydroxide acting as the base.Specifically,the cytosine donates its proton (H⁺)to neutralize the unstable negative charge that would have formed on the ribozyme.
Is Nakano's quote from Science consistent with the textbook's claim that RNA is a good candidate for the first life-form?

A)yes
B)no

Question 27

You isolate what you think is DNA from a tissue sample.Which of the following will verify that you do,indeed,have DNA (rather than some other type of molecule)?

A)You determine the molecule has carbon-carbon bonds.
B)You determine the molecule has primary and secondary structure.
C)You determine the molecule contains nitrogen and phosphorus.
D)None of answers A-C will verify that the isolated molecule is DNA.

Question 28

Why do researchers think the first self-replicating molecule was RNA?

A)RNA is the only type of molecule that can catalyze a chemical reaction.
B)RNA has the capacity to provide a template and is known to catalyze reactions (although no existing self-replicating molecules of RNA have been discovered).
C)Self-replicating molecules of RNA exist today,in human cells.
D)Fossil evidence of such a molecule was recently discovered.

Question 29

Use the following information when answering the corresponding question(s).
Shu-ichi Nakano reported in Science in February 2000 that "The RNA enzyme (ribozyme)from hepatitis delta virus catalyzes self-cleavage of a ...[chemical] ...bond." This reaction is inherently slow due to the formation of an unfavorable negative charge on the ribozyme.The author goes on to show that this self-cleavage is made faster by joining it with an acid-base reaction that neutralizes the negative charge.Nakano's model describes a positively charged cytosine base on the ribozyme acting as the acid,and magnesium hydroxide acting as the base.Specifically,the cytosine donates its proton (H⁺)to neutralize the unstable negative charge that would have formed on the ribozyme.
Refer to Nakano's quote.What can be inferred about the free-energy profile for the self-cleavage reaction from the information provided in the paragraph?

A)It must be endergonic.
B)It must be exergonic.
C)It must be endothermic.
D)It must be exothermic.

Question 30

The work of Bartel's group on the ribozyme RNA replicase supports which conclusion?

A)An RNA world could produce molecules that could self-replicate.
B)Natural selection does not work unless humans are present to help it.
C)DNA must have come before RNA.
D)Life cannot come from nonlife.

Question 31

Bartel's research group showed that an RNA replicase ribozyme could be created by _____.

A)carefully synthesizing a novel ribozyme monomer by monomer based on the sequence of known ribozymes
B)creating large numbers of random RNA segments and testing each one to see if any replicase activity was present
C)starting with random components and allowing selection to result in molecules that were better and better at replicating
D)examining protein replicases and reverse-engineering an RNA molecule capable of doing the same job

Question 32

Recall the Bartel lab group experiment to create a ribozyme from scratch.If they had created exact copies of each ribozyme (rather than creating copies with a few differences),what would have been the most likely result?

A)The ribozymes would have become more efficient with each round of selection.
B)The ribozymes would have stayed the same with each round of selection.
C)The ribozymes would have become less efficient with each round of selection.
D)The ribozymes would have stopped catalyzing reactions after just a few rounds of selection.

Question 33

Use the following information when answering the corresponding question(s).
Shu-ichi Nakano reported in Science in February 2000 that "The RNA enzyme (ribozyme)from hepatitis delta virus catalyzes self-cleavage of a ...[chemical] ...bond." This reaction is inherently slow due to the formation of an unfavorable negative charge on the ribozyme.The author goes on to show that this self-cleavage is made faster by joining it with an acid-base reaction that neutralizes the negative charge.Nakano's model describes a positively charged cytosine base on the ribozyme acting as the acid,and magnesium hydroxide acting as the base.Specifically,the cytosine donates its proton (H⁺)to neutralize the unstable negative charge that would have formed on the ribozyme.
In the acid-base reaction described in the preceding paragraph about Nakano's research on RNAs,a proton (H⁺)is being transferred.What is acting as the proton acceptor?

A)cytosine
B)magnesium hydroxide
C)the virus
D)cytosine,magnesium hydroxide,or the virus