Deck 4: Nucleic Acids and the Rna World

Question 1

Which of the following nitrogenous bases are purines?

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

Answer 1

D

Question 2

All organisms have which of the following attributes?

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.

Answer 2

E

Question 3

What forms the "backbone" of a nucleic acid?

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

Answer 3

A

Question 4

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 0.34m.
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 5

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

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

Question 6

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

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

Question 7

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

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

Question 8

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 9

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

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

Question 10

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 11

What does it mean when some bands on an autoradiograph are darker than others?

A)The concentration of the radioactive molecule in that band is higher.
B)This is normal because most of the radioactivity migrates to the same place.
C)The experiment failed because the radioactivity should be evenly distributed throughout the gel.
D)The darker bands represent larger molecules.

Question 12

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)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 13

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

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

Question 14

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 15

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

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 16

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 17

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

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

Question 18

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

Question 19

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 20

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 21

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 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 22

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

Question 23

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 24

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 25

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

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 26

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

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

Question 27

The term ribozyme describes what property of RNA molecules?

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

Question 28

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 29

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

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

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

Question 31

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)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 32

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

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

Question 34

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 35

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

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

Question 36

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

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

Question 37

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

Question 38

Which factors contributed to the lack of credit often given to Rosalind Franklin in the discovery of the structure of DNA?

A)Wilkins showed her photographs to Watson and Crick without her knowledge or permission.
B)She died at an early age so her career was shortened.
C)She was a woman working in a field dominated by men when sexism was more common.
D)All of the above apply.

Question 39

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

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

Question 40

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 natural selection to evolve molecules that were better and better at replicating.
D)examining protein replicases and reverse-engineering an RNA molecule capable of doing the same job.