Question 1

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?

Accepted Answer

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 2

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

Accepted Answer

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 3

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?

Accepted Answer

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 4

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

Accepted Answer

A)  RNA contains genetic information like DNA,but is not as stable.
B)  RNA can catalyze reactions,but not as well as 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 5

What can be inferred about the free-energy profile for the self-cleavage reaction from the information provided in the paragraph?

Accepted Answer

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

Question 6

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

Accepted Answer

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

Question 7

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

Accepted Answer

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

Question 8

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

Accepted Answer

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

Question 9

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

Accepted Answer

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

Question 10

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

Accepted Answer

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

Question 11

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

Accepted Answer

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 12

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?

Accepted Answer

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 0.34m.
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 ten times longer than they are wide.

Question 13

When doing gel electrophoresis,why do researchers add a "ladder" made up of molecules of known size?

Accepted Answer

A)  to help the molecules they are studying get through the gel more easily
B)  to help the researchers identify the size of each molecule after the separation has occurred
C)  to make sure the radioactivity doesn't interfere with the movement of the molecules that are being studied
D)  The molecules being studied would not show up without the ladder.

Question 14

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

Accepted Answer

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

Question 15

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

Accepted Answer

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

Question 16

Why is DNA said to be antiparallel?

Accepted Answer

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)  The DNA strands twist into a helix conformation once the bases have joined to form major and minor grooves.
C)  Each strand of the double helix is made up of a sugar phosphate backbone which runs in the 5'3' direction.
D)  DNA has polarity such that one strand runs in the 3'5' direction and the other in the 5'3' direction.

Question 17

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

Accepted Answer

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

Question 18

All organisms have which of the following attributes?

Accepted Answer

A)  They can reproduce.
B)  They can perform metabolism.
C)  They are composed of cells.
D)  They can reproduce and they are composed of cells.
E)  They can reproduce,perform metabolism,and are composed of cells.

Question 19

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

Accepted Answer

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

Question 20

Is Nakano's quote consistent with the textbook's claim that RNA is a good candidate for the first life-form?

Accepted Answer

A)  yes
B)  no

Exam 4: Nucleic Acids and the Rna World

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

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

Is Nakano's quote consistent with the textbook's claim that RNA is a good candidate for the first life-form?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Why is DNA said to be antiparallel?

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

All organisms have which of the following attributes?

Correct AnswerverifiedShow Answer

When doing gel electrophoresis,why do researchers add a "ladder" made up of molecules of known size?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

What can be inferred about the free-energy profile for the self-cleavage reaction from the information provided in the paragraph?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

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