1. 35S-labeled phage protein entered the host cell
The Hershey and Chase experiments using 35S- and 32P-labeled T2 bacteriophage supported the hypothesis that DNA is the genetic material because __________.
35S-labeled phage protein entered the host cell
new T2 progeny contained 35S-labeled protein
32P-labeled phage DNA did not enter the host cell
new T2 progeny contained 32P-labeled DNA
Answer: D
New T2 progeny did contain 32P-labeled DNA originally found in the labeled viruses that infected the bacteria (but not 35S-labeled protein), indicating that only DNA is passed on to progeny.

2. deoxyribonucleotide triphosphates (dNTPs) a DNA template
Which one of the following components is NOT required for DNA synthesis?
DNA polymerase
deoxyribonucleotide triphosphates (dNTPs)
a DNA template
ribonucleotide triphosphates (rNTPs)
Answer: D
Ribonucleotide triphosphates (rNTPs) are not required in DNA synthesis. They contain ribose instead of the deoxyribose found in DNA. rNTPs are the primary building blocks used for the synthesis of RNA molecules. 2

3. DNA directly serves as the template for protein synthesis
Data from pulse-chase studies showed that most mRNA leaves the nucleus and enters the cytoplasm. These data supported the hypothesis that __________.
DNA directly serves as the template for protein synthesis
mRNA serves as the template for protein synthesis
protein synthesis occurs in the nucleus
mRNA synthesis occurs in the cytoplasm
Answer: B
mRNAs must be synthesized using DNA templates in the nucleus (transcription). Furthermore, protein synthesis occurs in the cytoplasm at ribosomes (translation). Thus, the presence of mRNA in the cytoplasm supported this hypothesis. 3

4. Crick developed the adaptor hypothesis in response to all EXCEPT which of the following limitations of the conventionally held model for protein synthesis?
the unlikelihood that a folded RNA template could directly interact with hydrophobic amino acids
the unlikelihood that a folded RNA template could discriminate between amino acids of a similar size
the unlikelihood that a folded RNA template could form a cavity specific enough to fit only one given amino acid
the unlikelihood that a folded RNA template could directly interact with hydrophilic amino acids
Answer: D
The bases of RNA prefer hydrophilic interactions, so interaction with a hydrophilic amino acid is conceivable. This would not lead Crick to formulate the adaptor hypothesis. 4

5. Some codons must code for multiple amino acids.
The hypothesis that the genetic code consisted of groups of three nucleotides rather than groups of two nucleotides supports which of the following conclusions?
Some codons must code for multiple amino acids.
Every amino acid has at least one unique corresponding codon.
Every amino acid has only one corresponding codon.
All codons encode an amino acid.
Answer: B
With four different bases and groups of three nucleotides as the code, there are 43 or 64 possible codons and only 20 common amino acids. With groups of two nucleotides, there would be only 16 possible codons, and some codons would have to code for more than one amino acid. Thus, having 3 base pair codons ensures that every amino acid has at least one unique codon. 5

6. The synthesis of mRNA occurs in the 5 to 3 direction.
Which one of the following statements about the processes of transcription and translation is FALSE?
The synthesis of mRNA occurs in the 5 to 3 direction.
The synthesis of proteins occurs in the 5 to 3 direction.
The DNA template is read in the 3 to 5 direction during mRNA synthesis.
A transcribed mRNA and its non-template DNA strand are both oriented the same way with respect to the template DNA strand.
Answer: B
This statement is false. Protein synthesis results from the attachment of the amino-terminus of a free amino acid to the carboxy-terminus of a growing polypeptide. Only nucleic acids are synthesized in the 5 to 3 direction. 6

7. Using the table of the genetic code, identify which one of the following template DNA sequences encodes the amino acid tryptophan.
5-UGG-3
5-TGG-3
5-CCA-3
5-GGT-3
Answer: C
The codon for tryptophan is 5-UGG-3, which corresponds to the mRNA sequence. The template DNA sequence is reverse and complementary. 7