Cell Biology Chapter 4

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

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

The difference between the sugar in DNA and the sugar in RNA is that the sugar in DNA _____.

Contains one less O atom

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

DNA nucleotides contain a different sugar than RNA nucleotides.

Why do researchers think the first self-replicating molecule was RNA?

RNA can carry information and catalyze chemical reactions.

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?

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

When nucleotides polymerize to form a nucleic acid _____.

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

Which of the following descriptions best fits the class of molecules known as nucleotides?

a nitrogenous base, a phosphate group, and a sugar

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

cytosine, uracil, and thymine

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?

40

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?

5'-AGCT-3' with 5'-TCGA-3' 5'-ATGC-3' with 5'-GCAT-3' 5'-GCGC-3' with 5'-TATA-3' 5'-purine-pyrimidine-purine-pyrimidine-3' with 3'-purine-pyrimidine-purine-pyrimidine-5' All of these pairs are correct.

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

5'TGCAAT3'

Compare proteins to nucleic acids. Which of the following is true?

Both have primary and secondary structure.

Which of the following are purine nitrogenous bases?

Guanine and adenine

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?

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?

It does not function as a catalyst.

NA 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 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?

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

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 _____.

Phosphorous

If 14C-labeled uracil is added to the growth medium of cells, what macromolecules will be labeled?

RNA

Which of the following is a difference between RNA and DNA

RNA has ribose sugar and DNA has deoxyribose sugar

What is the difference between a ribonucleotide and a deoxyribonucleotide?

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

DNAase is an enzyme that catalyzes the hydrolysis of the covalent bonds that join nucleotides together. What would first happen to DNA molecules treated with DNAase?

The phosphodiester bonds between deoxyribose sugars would be broken.

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?

The phosphodiester linkages of the polynucleotide backbone would be broken

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?

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

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

There is no difference

What is the structural feature that allows DNA to replicate?

complementary pairing of the nitrogenous bases

Which of the following are pyrimidine nitrogenous bases?

cytosine and uracil

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

double antiparallel helical strands

One of the primary functions of RNA molecules is to

function in the synthesis of proteins

If cells are grown in a medium containing radioactive 32P-labeled phosphate, which of these molecules will be labeled?

glucose

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

nucleotides

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

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

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 _____.

stayed the same with each round of selection

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

their phosphate groups