Nucleic Acids

Question 1

The DNA double helix:
A)is destabilized by hydrogen bonding
B) is stabilized by the hydrophobic effect
C)is a linear molecule with no three-dimensional shape
D)does not associate with protein
E)is stabilized by Cl-

Answer 1

B) is stabilized by the hydrophobic effect
Hydrogen between complementary nucleotides stabilizes the DNA double helix, and the double helix is stabilized by base stacking interactions and the hydrophobic effect. The DNA double helix has a three-dimensional shape to it (like all molecules), and associated with proteins such as histones and transcription factors. Cations such as Mg 2+ stabilize the DNA double helix.

Question 2

Each of the following statements describes a difference between RNA and DNA, except:
A)DNA contains deoxyribose while RNA contains ribose
B) thymine base in DNA is replaced by uracil in RNA
C)DNA typically occurs in a double helix conformation while RNA does not.
D)RNA cana catalyze chemical reactions while DNA does not
E)DNA contains only purines while RNA contains only pyramidines

Answer 2

E)DNA contains only purines while RNA contains only pyramidines
Both DNA and RNA contain both purines (G,C) and pyramidines (A,T or U). All other statements are correct

Question 3

Yarmouth county of Nova Scotia has the highest prevalence in the world of Niemann-Pick C1( NPC1) disease, a fatal inherited disorder of intracellulat cholesterol transport. Most Nova Scotian NPC1 patients are of Acadian descent and are homozygous for a point mutation that results in replacement of glycine with tryptophan at position 992 of the amino acid sequence (G992W). This would be an example of what type of mutation?
A)nonsense
B) silent
C)missense
D) frame shift
E) splice variant

Answer 3

C) missense
Resulting in substitution with a different amino acid. Nonsense and silent mutations introduce stop codons and so not result in amino acid substitutions, respectively. Frameshift mutations change the translational reading frame,while splice variants result in incorrect exon joining.

Question 4

Which of the following statements is false?
A)G-quadruplexes may have functional roles in the body
B)DNA sequences have a low information density
C)the DNA double helix has a polar exterior
D) DNA can be used to create 3D objects
E)hydrogen bonding is important for determining DNA base complementarity

Answer 4

B)DNA sequences have a low information density