Ch 4 Mastering Biology

In eukaryotic cells DNA has the appearance of a _____. A) single strand B) letter U C) double helix D) triple helix E) circle

C) double helix

Which of the following best describes DNA's secondary structure? beta-pleated sheet double parallel helical strands turn-loop-turn double antiparallel helical strands

double antiparallel helical strands

An RNA molecule that can catalyze chemical reactions is called a_____. A) stem-loop B) ribozyme C) protein D) Tetrahymena

B) ribozyme Altman and Cech shared a Nobel Prize for showing that RNA could catalyze reactions. Such catalytic RNAs were termed ribozymes.

DNA and mRNA differ with respect to ... (b) the kinds of purines they contain. (a) the kind of sugar they contain. Both (a) and (b). (c) how many kinds of nucleotides are used to make the polymer. (d) the ability to make a double helix

(a) the kind of sugar they contain. RNA uses ribose; DNA uses deoxyribose. The polymer names reflect this difference: RNA is short for Ribonucleic acid; DNA is short for deoxyribonucleic acid.

Current best estimates suggest that life has been on Earth for how long? 3.5 thousand years 3.5 million years 3.5 billion years 3.5 trillion years

3.5 billion years

Nucleic acids are assembled in the _____ direction. 2' to 3' 4' to 5' 5' to 3' 1' to 5' 5' to 1'

5' to 3' New nucleotides are added to the 3' end of a growing polynucleotide.

The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases. A) hydrogen bonds B) hydrophilic interactions C) S—S bonds D) ionic bonds E) covalent bonds

A) hydrogen bonds Nitrogenous base pairs are joined by hydrogen bonds.

The work of Bartel's group on the ribozyme RNA replicase supports which conclusion? An RNA world could produce molecules that could self-replicate. Natural selection requires human oversight. Life cannot come from nonlife. DNA must have come before RNA.

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

Why is it that RNA can catalyze reactions but DNA cannot? A) The primary structure of RNA is fundamentally different than the primary structure of DNA. B) The sugar of RNA is much more reactive than the sugar of DNA. C) The bases of RNA are much more reactive than the bases of DNA. D) The phosphate groups of RNA are much more reactive than the phosphate groups of DNA.

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

The chemical evolution theory states that the first living molecule needed these two attributes: A) It could acquire energy and catalyze reactions. B) It could maintain homeostasis and acquire energy. C) It could serve as a replication template and could catalyze reactions. D) It could acquire energy and serve as a replication template.

C) It could serve as a replication template and could catalyze reactions. The first living molecule needed to be able to copy itself, requiring that it could catalyze reactions and serve as a template for replication.

DNA is composed of building blocks called _____. A) nucleic acids B) Gs C) nucleotides D) adenines E) amino acids

C) nucleotides

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) carefully synthesizing a novel ribozyme monomer by monomer based on the sequence of known ribozymes C) starting with random components and allowing selection to result in molecules that were better and better at replicating D) 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

In a DNA double helix, what kind of chemical bonds form between the complementary nitrogenous bases? A) polar covalent bonds B) phosphodiester bonds C) nitrogen bonds D) hydrogen bonds

D) hydrogen bonds Three hydrogen bonds form between GC base pairs and two hydrogen bonds form between AT base pairs.

Which statement helps to explain how DNA stores hereditary information? DNA is made from thousands of kinds of monomers. DNA is a self-replicating type of protein. DNA contains four kinds of nitrogenous bases. DNA contains 20 kinds of amino acids. DNA binds a master copy of each kind of protein.

DNA contains four kinds of nitrogenous bases. Information is stored in the sequence of nitrogenous bases along the DNA polymer. The bases include two kinds of pyrimidines and two kinds of purines.

What holds the strands of the DNA double helix together? Hydrogen bonds between purines and pyrimidines. Attractions between the ionized phosphates. Attractions between polar sugars. Covalent bonds between A and T, and between C and G. Proteins that bind to DNA bases.

Hydrogen bonds between purines and pyrimidines. A and G are purines; C and T are pyrimidines. Hydrogen bonds link them.

Researchers hypothesize that the first self-replicating molecule may have been ____. This is known as the ______world hypothesis. RNA, RNA DNA, RNA lipid, lipid protein, protein

RNA, RNA RNA is a strong candidate for the first self-replicating molecule because it can both function as an enzyme and serve as a template for replication.

How are the structures of RNA and DNA similar? They both have the same tertiary structure. They both contain the sugar ribose. Their sugar-phosphate backbones are formed by phosphodiester linkages. Adenine pairs with thymine in both.

Their sugar-phosphate backbones are formed by phosphodiester linkages. Covalent phosphodiester bonds join adjacent nucleotides.

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

are information-containing molecules

If you measure the amounts of the bases in any sample of DNA, you'll find that ... the amount of A = the amount of G; the amount of T = the amount of C. the amount of A + the amount of G = the amount of T + the amount of C. the amount of A + the amount of C = the amount of G + the amount of U. the amount of A + the amount of T = the amount of G + the amount of C. None of the above.

the amount of A + the amount of G = the amount of T + the amount of C. For every A there's a T; for every G there's a C.

In a nucleotide, the nitrogenous base is attached to the sugar's _____ carbon and the phosphate group is attached to the sugar's _____ carbon. 1' ... 3' 2' ... 1' 1' ... 2' 1' ... 5' 2' ... 3'

1' ... 5'

A nucleotide is composed of a(n) _____. A) glycerol, a nitrogen-containing base, and a five-carbon sugar B) phosphate group, a nitrogen-containing base, and a hydrocarbon C) sulfhydryl group, a nitrogen-containing base, and a five-carbon sugar D) amino group, a nitrogen-containing base, and a five-carbon sugar E) phosphate group, a nitrogen-containing base, and a five-carbon sugar

E) phosphate group, a nitrogen-containing base, and a five-carbon sugar

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

RNA

Why do researchers think the first self-replicating molecule was RNA? Self-replicating molecules of RNA exist today, in human cells. Fossil evidence of such a molecule was recently discovered. RNA can carry information and catalyze chemical reactions. RNA is the only type of molecule that can catalyze a chemical reaction.

RNA can carry information and catalyze chemical reactions.

Which of the following is a difference between RNA and DNA? RNA is single-stranded and DNA is usually triple-stranded. RNA is made from nucleotide monomers and DNA is made from amino acid monomers. RNA has ribose sugar and DNA has deoxyribose sugar. DNA contains adenine and RNA does not.

RNA has ribose sugar and DNA has deoxyribose sugar.

What is the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in RNA? The sugar molecule is different. The number of phosphates is three instead of two. The nitrogen-containing base is different. There is no difference. The number of phosphates is three instead of one.

There is no difference.

Which of these nitrogenous bases is found in DNA but not in RNA? uracil cytosine guanine adenine thymine

thymine

In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand. cytosine ... thymine uracil ... cytosine guanine ... adenine cytosine ... uracil thymine ... cytosine

thymine ... cytosine This is referred to as specific base pairing.

The information in DNA tells a cell how to make ... (a) proteins. (b) DNA. (c) tRNA. Both (a) and (b). (a), (b), and (c).

(a), (b), and (c). The information in DNA tells how to make every nucleic acid and protein that the cell's parent could make.

RNA nucleotides contain __________ than DNA nucleotides. less oxygen more oxygen less phosphorus different purines None of the above.

more oxygen RNA uses the sugar ribose, which has one more oxygen atom than the sugar used in DNA (deoxyribose).

Which statement expresses a real difference between DNA and RNA? (a) DNA can make a double helix; RNA cannot. (b) DNA is much longer than RNA. (c) DNA has more kinds of bases than RNA. Both (a) and (b). (a), (b), and (c).

(b) DNA is much longer than RNA. RNA is made by copying short segments of DNA.

Which of the following statements about the 5' end of a polynucleotide strand of RNA is correct? A) The 5' end has a phosphate 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 is the fifth position on one of the nitrogenous bases. D) The 5' end has a carboxyl group attached to the number 5 carbon of ribose. E) The 5' end has a hydroxyl group attached to the number 5 carbon of ribose.

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

How would you expect the structure of ribozymes in organisms that grow in very hot environments, such as hot springs or deep-sea vents, to differ from those in organisms that grow in cooler environments? A) The hairpins would have more G's and C's in the primary structure. B) These ribozymes would exhibit no tertiary structure. C) These ribozymes would have more hairpin secondary structures. D) The hairpins would have more A's and U's in the primary structure.

A) The hairpins would have more G's and C's in the primary structure.

The condensation reaction that forms nucleic acid polymers occurs between a _____ group on one nucleotide and a _____ group on a second nucleotide. A) nitrogenous base, nitrogenous base B) phosphate, hydroxyl C) carbon, carbon D) nitrogenous base, sugar

B) phosphate, hydroxyl A phosphate group on the 5' carbon of the sugar forms a phosphodiester bond with a hydroxyl on the 3' carbon of a second sugar, forming a sugar-phosphate backbone.

Which of these is a difference between a DNA and an RNA molecule? A) DNA contains uracil, whereas RNA contains thymine. B) DNA contains nitrogenous bases, whereas RNA contains phosphate groups. C) DNA contains five-carbon sugars, whereas RNA contains six-carbon sugars. D) DNA is a polymer composed of nucleotides, whereas RNA is a polymer composed of nucleic acids. E) DNA is usually double-stranded, whereas RNA is usually single-stranded.

E) DNA is usually double-stranded, whereas RNA is usually single-stranded. With some exceptions, DNA is a double-stranded molecule and RNA is a single-stranded molecule.

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

E) These numbers tell us there are ten rungs, or steps, on the DNA "ladder" for every turn of the helix.

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

E) purines is always the same as pyrimidines

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? It is not stable enough to have withstood early Earth's harsh atmosphere. It does not function as a catalyst. DNA only has four types of bases. Therefore, DNA cannot adapt and evolve. 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.

If life exists or originated on another planet, most scientists today believe that it is which of the following planets? Mars Saturn Neptune Venus

Mars

Which of the following is true regarding current scientific thought? DNA originated before RNA. RNA originated before DNA. RNA and DNA originated at the same time. RNA and DNA are the same thing.

RNA originated before DNA.

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

The strands of the double helix are complementary.

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

complementary pairing of the nitrogenous bases

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

function in the synthesis of proteins