ch 16 bio 101

Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately, what percentage of the nucleotides in this sample will be thymine?

A) 12

Avery and his colleagues purified various chemicals from pathogenic bacteria and showed that ____ was (were) the transforming agent.

A) DNA

For a couple of decades, biologists knew the nucleus contained DNA and proteins. The prevailing opinion was that the genetic material was proteins, and not DNA. The reason for this belief was that proteins are more complex than DNA. This is because

A) Proteins have a greater variety of three-dimensional forms than does DNA.

What kind of chemical bond is found between paired bases of the DNA double helix?

A) hydrogen

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in its

A) sequence of bases

Tobacco mosaic virus has RNA rather than DNA as its genetic material. In a hypothetical situation where RNA from a tobacco mosaic virus is mixed with proteins from a related DNA virus, the result could be a hybrid virus. If that virus were to infect a cell and reproduce, what would the resulting "offspring" viruses be like?

A) tobacco mosaic virus

Phage with labeled proteins or DNA was allowed to infect bacteria. It was shown that the DNA, but not the protein, entered the bacterial cells, and was therefore the genetic material.

B) Alfred Hershey and Martha Chase

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

B) DNA contains phosphorus, but protein does not.

The following scientists made significant contributions to our understanding of the structure and function of DNA. Place the scientists' names in the correct chronological order, starting with the first scientist(s) to make a contribution.

B) II, I, III, V, IV

In his transformation experiments, Griffith observed that

B) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.

When T2 phages infect bacteria and make more viruses in the presence of radioactive sulfur, what is the result?

B) The viral proteins will be radioactive.

All of the following can be determined directly from X-ray diffraction photographs of crystallized DNA except the

B) helical shape of DNA.

Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA.

C) Oswald Avery, Maclyn McCarty, and Colin MacLeod

Chargaff's analysis of the relative base composition of DNA was significant because he was able to show that

C) the amount of A is always equivalent to T, and C to G.

After mixing a heat-killed, phosphorescent strain of bacteria with a living non-phosphorescent strain, you discover that some of the living cells are now phosphorescent. The best evidence that the ability to fluoresce is a heritable trait would be an observation that

D) Descendants of the living cells are also phosphorescent.

In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine

D) Erwin Chargaff

Which of the following statements does not apply to the Watson and Crick model of DNA?

D) The two strands of the helix are held together by covalent bonds.

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

E) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

What does transformation involve in bacteria?

E) assimilation of external DNA into a cell

The DNA double helix has a uniform diameter because ____, which have two rings, always pair with ____, which have one ring.

a. purines; pyrimidines