Biology DPMA

In his work with pneumonia-causing bacteria & mice, Griffith found that 

• the protein coat from pathogenic cells was able to transform nonpathogenic cells.
• heat-killed pathogenic cells caused pneumonia.
• some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
• the polysaccharide coat of bacteria caused pneumonia.

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

• DNA polymerase can join new nucleotides to the 3' end of the preexisting strand.
• Helicases and single-strand binding proteins work at the 5' end.
• The origins of replication occur only at the 5' end.
• DNA ligase works only in the 3' to 5' direction

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

• A = G
• A + G = C + T
• A + T = G + G
• A = C

The elongation of the leading strand during DNA synthesis 

• progresses away from the replication fork.
• occurs in the 3' to 5' direction.
• produces Okazaki fragments
• depends on the action of DNA polymerase

In a nucleosome, the DNA is wrapped around

• polymerase molecules.
• ribosomes.
• histones.
• a thymine dimer.

E. coli cells grown on N-15 medium are transferred to N-14 medium and allowed to grow for 2 more generations.  DNA extracted from these cells is centrifuged.  What density distribution of DNA would you expect in this experiment?

• one high-density and one low-density band
• One intermediate-density band
• one high-density and one intermediate-density band
• one low-density and one intermediate-density band

A student isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication.  After adding some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long.  What has the student probably left out of the mixture?

• DNA polymerase
• DNA ligase
• Okazaki fragments
• primase

In eukaryotic cells, transcription cannot begin until 

• the two DNA strands have completely separated and exposed the promoter.
• several transcription factors have bound to the promoter.
• the 5' caps are removed from the mRNA.
• the DNA introns are removed from the template.

Which of the following is NOT true of a codon?

• It may code for the same amino acid as another codon.
• It never codes for more than one amino acid.
• It extends from one end of a tRNA molecule.
• It is the basic unit of the genetic code.

The anticodon of a particular tRNA molecule is 

• complementary to the corresponding mRNA codon.
• complementary to the corresponding triplet in rRNA.
• the part of tRNA that bonds with a specific amino acid.
• catalytic, making the tRNA a ribozyme.