In his transformation experiments, what did Griffith observe?

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

• Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.

What does transformation involve in bacteria?

• the infection of cells by a phage DNA molecule

• assimilation of external DNA into a cell

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

• DNA contains phosphorus, but protein does not.

• DNA contains nitrogen, whereas protein does not.

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 wonʹt this experiment work?

• Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.

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

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?

• 12%

• 24%

• 31%

• 38%

Chargaffʹs analysis of the relative base composition of DNA was significant because he was able to show that

• the relative proportion of each of the four bases differs within individuals of a species.

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

Tags

NGSS.HS-LS1-1

Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?

• the diameter of the helix

• the rate of replication

Why does the DNA double helix have a uniform diameter?

• Purines pair with pyrimidines.

• Deoxyribose sugars bind with ribose sugars.

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

• hydrogen

• ionic

• covalent

In an analysis of the nucleotide composition of DNA, which of the following will be found?

• A = G and C = T

• A + C = G + T