The process by which one strain of bacterium is apparently changed into another strain is called

1. transcription.

2. transformation.

3. duplication.

4. replication.

Bacteriophages are

1. a form of bacteria.

2. enzymes.

3. coils of DNA.

4. viruses.

Which of the following researchers used radioactive markers in experiments to show that DNA was the genetic material in cells?

1. Frederick Griffith

2. Oswald Avery

3. Alfred Hershey and Martha Chase

4. James Watson and Francis Crick

Before DNA could definitively be shown to be the genetic material in cells, scientists had to show that it could

1. tolerate high temperatures.

2. carry and make copies of information.

3. be modified in response to environmental conditions.

4. be broken down into small subunits.

Briefly describe the conclusion that could be drawn from the experiments of Frederick Griffith.

What was the key factor that allowed Hershey and Chase to show that DNA alone carried the genetic information of a bacteriophage?

Interpret Visuals Look back at Griffith's experiment shown in Figure 12–1. Describe the occasion in which the bacterial DNA withstood conditions that killed the bacteria. What happened to the DNA during the rest of the experiment?

Evaluate Avery and his team identified DNA as the molecule responsible for the transformation seen in Griffith's experiment. How did they control variables in their experiment to make sure that only DNA caused the effect?

nucleotide does NOT contain

1. a 5-carbon sugar.

2. an amino acid.

3. a nitrogen base.

4. a phosphate group.

According to Chargaff's rule of base pairing, which of the following is true about DNA?

1. A = T, and C = G

2. A = C, and T = G

3. A = G, and T = C

4. A = T = C = G

The bonds that hold the two strands of DNA together come from

1. the attraction of phosphate groups for each other.

2. strong bonds between nitrogenous bases and the sugar-phosphate backbone.

3. weak hydrogen bonds between nitrogenous bases.

4. carbon-to-carbon bonds in the sugar portion of the nucleotides.

Describe the components and structure of a DNA nucleotide.

Explain how Chargaff's rule of base pairing helped Watson and Crick model DNA.

What important clue from Rosalind Franklin's work helped Watson and Crick develop their model of DNA?

Why is it significant that the two strands of DNA are antiparallel?

Use Models How did Watson and Crick's model of the DNA molecule explain base pairing?

Infer Rosalind Franklin's X-ray pattern showed that the distance between the two phosphate-sugar backbones of a DNA molecule is the same throughout the length of the molecule. How did that information help Watson and Crick determine how bases are paired?