bio chapter 4

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.

It could be either, because both molecules have catalytic properties.

DNA is the main hereditary material of all life. However, DNA lacks one important characteristic for the first forms of life. 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) DNA only has four types of bases. Therefore, DNA cannot adapt and evolve. D) The type of sugar found in DNA is too complicated to have been present early in Earth's history.

It does not function as a catalyst.

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.

One end has an unlinked 3' carbon; the other end has an unlinked 5 carbon.

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

a covalent bond forms between the sugar of one nucleotide and the phosphate of a second

Both DNA and RNA ________. A) are information-containing molecules B) show primary, secondary, tertiary, and quaternary structure C) are highly reactive catalysts in cells D) naturally occur as a double helix

are information-containing molecules

Which of the following are pyrimidine nitrogenous bases? A) guanine and adenine B) cytosine and uracil C) thymine and guanine D) ribose and deoxyribose E) adenine and thymine

cytosine and uracil

Which of the following includes all of the pyrimidines found in RNA and DNA? A) cytosine and uracil B) cytosine and thymine C) cytosine, uracil, and thymine D) cytosine, uracil, and guanine

cytosine, uracil, and thymine

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

double antiparallel helical strands

If cells are grown in a medium containing radioactive 32P-labeled phosphate, which of these molecules will be labeled? A) proteins B) cellulose C) amino acids D) nucleic acids E) glucose

glucose

Which of the following are purine nitrogenous bases? A) cytosine and guanine B) guanine and adenine C) adenine and thymine D) thymine and uracil E) uracil and cytosine

guanine and adenine

Nucleic acids are polymers made up of which of the following monomers? A) nucleotides B) ribose sugars C) amino acids D) nitrogenous bases E) phosphates

nucleotides

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

stayed the same with each round of selection

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

the sugar and the base

A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be composed of ________. A) 120 adenine and 120 uracil molecules B) 120 thymine and 120 adenine molecules C) 120 cytosine and 120 thymine molecules D) 120 adenine and 120 cytosine molecules E) 120 guanine and 120 thymine molecules

120 thymine and 120 adenine molecules

If a double-stranded DNA sample were composed of 10 percent thymine, what would be the percentage of guanine? A) 10 B) 20 C) 40 D) 80 E) It is impossible to tell from the information given.

40

Compare proteins to nucleic acids. Which of the following is TRUE? A) Both have primary and secondary structure. B) Both contain sulfur. C) Both are used as templates to synthesize polymers D) Both have monomers, which contain phosphorus.

Both have primary and secondary structure.

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) DNA nucleotides contain a different sugar than RNA nucleotides. D) DNA contains the base uracil, whereas RNA contains the base thymine. E) The bases in DNA contain sulfur, whereas the bases in RNA do not contain sulfur.

DNA nucleotides contain a different sugar than RNA nucleotides.

What is the structural feature that allows DNA to replicate? A) sugar-phosphate backbone B) complementary pairing of the nitrogenous bases C) disulfide bonding (bridging) of the two helixes D) twisting of the molecule to form an α-helix E) three-component structure of the nucleotides

complementary pairing of the nitrogenous bases

The difference between the sugar in DNA and the sugar in RNA is that the sugar in DNA ________. A) is a six-carbon sugar and the sugar in RNA is a five-carbon sugar B) can form a double-stranded molecule C) is an aldehyde sugar and the sugar in RNA is a keto sugar D) is in the α configuration and the sugar in RNA is in the β configuration E) contains one less oxygen atom

contains one less oxygen atom

One of the primary functions of RNA molecules is to ________. A) transmit genetic information to offspring B) function in the synthesis of proteins C) make a copy of itself, thus ensuring genetic continuity D) act as a pattern or blueprint to form DNA E) form the genes of higher organisms

function in the synthesis of proteins

Which of the following did Watson and Crick already know when they were trying to determine the structure of DNA? The number of ________. A) purines is always larger than the number of pyrimidines B) pyrimidines is always larger than purines C) cytosines is always the same as adenines D) guanines is always the same as thymines E) purines is always the same as pyrimidines

purines is always the same as pyrimidines

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

starting with random components and allowing selection to result in molecules that were better and better at replicating

What feature of single nucleotides 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

their phosphate groups

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

there is no difference

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA? A) 5'-purine-pyrimidine-purine-pyrimidine-3' with 3'-purine-pyrimidine-purine-pyrimidine-5' B) 5'-AGCT-3' with 5'-TCGA-3' C) 5'-GCGC-3' with 5'-TATA-3' D) 5'-ATGC-3' with 5'-GCAT-3' E) All of these pairs are correct.

5'-ATGC-3' with 5'-GCAT-3'

If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence ________. A) 5'TAACGT3' B) 5'TGCAAT3' C) 5'UAACGU3' D) 3'UAACGU5' E) 5'UGCAAU3'

5'TGCAAT3'

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) RNA molecules with variable characteristics could catalyze protein synthesis. C) Ribozymes had to be present in the first cells to generate copies of the genetic material D) Ribozymes were produced randomly through natural selection.

An RNA world could produce molecules that could self-replicate.

If 14C-labeled uracil is added to the growth medium of cells, what macromolecules will be labeled? A) phospholipids B) DNA C) RNA D) both DNA and RNA E) proteins

RNA

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 can carry information and catalyze chemical reactions. C) Self-replicating molecules of RNA exist today, in human cells. D) Fossil evidence of such a molecule was recently discovered.

RNA can carry information and catalyze chemical reactions.

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.

Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.

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

The 5' end has a phosphate group attached to the number 5 carbon of ribose.

DNA double helices are soluble in water but insoluble in alcohol. How do these physical properties reflect the chemical structure of the DNA molecule? A) The charged phosphate groups and sugars of DNA are hydrophilic. B) The purine and pyrimidine bases are hydrophilic. C) The 5 prime to 3 prime polarity of DNA makes it soluble in water but not in alcohol. D) The charged R-groups of DNA are hydrophilic.

The charged phosphate groups and sugars of DNA are hydrophilic.

Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes? A) The two strands of the double helix would separate. B) The phosphodiester linkages of the polynucleotide backbone would be broken. C) The purines would be separated from the deoxyribose sugars. D) The pyrimidines would be separated from the deoxyribose sugars. E) All bases would be separated from the deoxyribose sugars.

The phosphodiester linkages of the polynucleotide backbone would be broken.

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 prime to 3 prime.

The strands of the double helix are complementary.

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.

The sugar of RNA is much more reactive than the sugar of DNA.

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 along the length of the strand.

The width of the double helix would vary along the length of the strand.

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 demonstrate 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.

These numbers demonstrate there are 10 rungs, or steps, on the DNA "ladder" for every turn of the helix.

Which of the following descriptions best fits the class of molecules known as nucleotides? A) a nitrogenous base and a phosphate group B) a nitrogenous base and a sugar C) a nitrogenous base, a phosphate group, and a sugar D) a phosphate group and an adenine or uracil E) a sugar and a purine or pyrimidine

a nitrogenous base, a phosphate group, and a sugar

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

phosphorous