Deck 4: Nucleic Acids and the Rna World

Question 1

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

Answer 1

A

Question 2

In the secondary structure of DNA, the a- helical twists are organized into

A) large and minor grooves.
B) major and minor grooves.
C) large and small grooves.
D) major and small grooves.

Answer 2

B

Question 3

Which of the following statements best summarizes the differences between DNA and RNA?

A) DNA encodes hereditary information, whereas RNA does not.
B) The bases in DNA contain sugars, whereas the bases in RNA do not contain sugar.
C) The bases in DNA contain sulfur, whereas the bases in RNA do not contain sulfur.
D) DNA contains the base uracil, whereas RNA contains the base thymine.
E) DNA nucleotides contain a different sugar than RNA nucleotides.

Answer 3

E

Question 4

Which of the following nitrogenous bases is found in RNA, but not DNA?

A) adenine
B) guanine
C) thymine
D) uracil

Question 5

What is the difference if any) between the structure of ATP and the structure of the precursor of the A nucleotide in RNA?

A) The sugar molecule is different.
B) The number of phosphates is three instead of two.
C) The number of phosphates is three instead of one.
D) The nitrogen- containing base is different.
E) There is no difference.

Question 6

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

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

Question 7

Why is DNA said to be antiparallel?

A) The two strands of DNA are joined together via complementary base pairing such that AT run in the 3'5' direction and CG run in the 5'3' direction.
B) Each strand of the double helix is made up of a sugar phosphate backbone which runs in the 5'3' direction.
C) DNA has polarity such that one strand runs in the 3'5' direction and the other in the 5'3' direction.
D) The DNA strands twist into a helix conformation once the bases have joined to form major and minor grooves.

Question 8

By convention, the sequence of bases in a nucleic acid is always written in which direction?

A) 3' - 5'
B) amino to carboxyl
C) 5' - 3'
D) carboxyl to amino

Question 9

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

Question 10

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

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

Question 11

If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence

A) 5'TGCAAT3'.
B) 5'TAACGT3'.
C) 5'UAACGU3'.
D) 3'UAACGU5'.
E) 5'UGCAAU3'.

Question 12

What forms the "backbone" of a nucleic acid?

A) purine and pyrimidine pairs, hydrogen- bonded to each other
B) a chain of sugar and phosphate groups, linked through phosphodiester bonds
C) a double helix of antiparallel strands
D) a chain of amino and carboxyl groups, linked via peptide bonds

Question 13

What is the difference between a ribonucleotide and a deoxyribonucleotide?

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

Question 14

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

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

Question 15

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

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

Question 16

Which of the following statements about the 5' end of a polynucleotide strand of RNA is correct?

A) The 5' end has a hydroxyl group attached to the number 5 carbon of ribose.
B) The 5' end has phosphate attached to the number 5 carbon of the nitrogenous base.
C) The 5' end has a carboxyl group attached to the number 5 carbon of ribose.
D) The 5' end is the fifth position on one of the nitrogenous bases.
E) The 5' end has a phosphate group attached to the number 5 carbon of ribose.

Question 17

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

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

Question 18

A nucleotide is made up of which of the following subunits?

A) a 5- carbon sugar and a nitrogenous base
B) a 5- carbon sugar, an amino group, and an "R- group"
C) a 5- carbon sugar and a phosphate group
D) a 5- carbon sugar, a phosphate group, and a nitrogenous base

Question 19

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

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

Question 20

Which of the following nitrogenous bases are purines?

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

Question 21

Use the following information when answering the corresponding questions).
Shuichi 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.
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 exothermic.
B) It must be endergonic.
C) It must be exergonic.
D) It must be endothermic.

Question 22

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

A) examining protein replicases and reverse- engineering an RNA molecule capable of doing the same job.
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 natural selection to evolve molecules that were better and better at replicating.
D) carefully synthesizing a novel ribozyme monomer by monomer based on the sequence of known ribozymes.

Question 23

Which of the following is not a difference between RNA and DNA?

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

Question 24

If a molecule of DNA contains 10% cytosine, it has guanine and adenine respectively.

A) 40%; 10%
B) 10%; 40%
C) 10%; 80%
D) 10%; 45%
E) 40%; 40%

Question 25

Why do many researchers consider RNA to be the best candidate for the first life- form?

A) It is simple in structure.
B) It carries more information than any other molecule.
C) All of its nucleotide components have been created under laboratory conditions that mimic early Earth.
D) It is capable of self- replication and catalysis.

Question 26

What is the structural feature that allows DNA to replicate?

A) three- component structure of the nucleotides
B) disulfide bonding bridging) of the two helixes
C) complementary pairing of the nitrogenous bases
D) sugar- phosphate backbone
E) twisting of the molecule to form an a- helix

Question 27

Use the following information when answering the corresponding questions).
Shuichi 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) ionic
C) glycosidic
D) phosphodiester

Question 28

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

Question 29

Hairpins and stem- and- loop patterns make up what part of RNA's structure?

A) secondary
B) tertiary
C) quaternary
D) primary

Question 30

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) DNA always goes from 5 to 3.
D) The strands of the double helix are complementary.

Question 31

Use the following information when answering the corresponding questions).
Shuichi 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.
If the cytosine is positively charged +) before self- cleavage, what would its charge be after self- cleavage?

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

Question 32

Use the following information when answering the corresponding questions).
Shuichi 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, a proton H+) is being transferred. What is acting as the proton acceptor?

A) cytosine
B) magnesium hydroxide
C) the virus
D) A, B, or C. Any one of these can act as the acceptor.

Question 33

If DNA is heated to 95°C, the bonds between complementary strands break, resulting in two single strands of DNA. In this process, which bases will separate first because they have less hydrogen bonds between them?

A) adenine and cytosine
B) guanine and thymine
C) guanine and cytosine
D) adenine and thymine

Question 34

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

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

Question 35

The "information system" of the cell involves stable genetic information being stored as , which can be used to make a "disposable" relatively short- lived) copy of this information as .

A) DNA; RNA
B) RNA; RNA
C) RNA; DNA
D) DNA; DNA

Question 36

What is responsible for holding the two strands together in the DNA double helix?

A) hydrogen bonds
B) ionic bonds
C) covalent bonds
D) phosphodiester bonds

Question 37

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

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

Question 38

The term ribozyme describes what property of RNA molecules?

A) its shape
B) catalytic
C) the fact that part of RNA molecules can be double- stranded similar to DNA
D) single- stranded

Question 39

Why is DNA more appropriate than RNA as the information storing molecule of the cell?

A) DNA has the ability to catalyze reactions and make proteins.
B) RNA has only four different bases and thus cannot carry enough information.
C) DNA is far less reactive than RNA, and thus the information sequence is more stable.
D) RNA is more stable than DNA and has the ability to catalyze reactions.

Question 40

Use the following information when answering the corresponding questions).
Shuichi 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 consistent with the textbook's claim that RNA is a good candidate for the first life- form?

A) yes
B) no