ESSENTIAL/INTRODUCTORY CELL BIOLOGY AND BIOCHEMISTRY
SAMPLE QUESTIONS ON NUCLEIC ACIDS AND MACROMOLECULES
1.Which of the following statements about the structure of DNA shown in the figure on the right is false?
The width of the DNA molecule is variable since it can accommodate nucleotides containing varying numbers of nitrogen-based "rings." Hydrogen bonds determine which nitrogenous bases can pair together. A total of 10 pairs of nucleotides are included in each complete "turn" of the double helix. The outer surface contains two sugar phosphate backbones
The distance between the nitrogenous base pair "rungs" of the helix is about 0.34nm.
2.In the Meselson-Stahl experiment bacteria grown in heavy nitrogen (N15) were transferred to light nitrogen (N14) and the density of the DNA monitored over successive rounds of replication. After two rounds of replication both light DNA and hybrid (light/heavy) DNA was present. What result would you expect if the bacteria were allowed to undergo one more round of replication?
One band of heavy DNA One band of hybrid DNA
One band of hybrid DNA
One band of light DNA
One band of light DNA and one band of hybrid DNA
One band of light DNA and a second band between light and hybrid DNA
3.Put the following events in protein synthesis in chronological order.
1 After peptide linkage, the empty P site tRNA prepares to leave the ribosome
2 The ribosome releases the empty tRNA as it translocates the length of one codon
3 The next tRNA binds to the A site
4 A tRNA is positioned at the UAG start codon
5 The amino acid at the P site is transferred to the amino acid attached to the tRNA at the A site
6 The A site is now free for the next incoming tRNA
4.Which one of the following is correct for Trehalose