DNA Class test-1

Which characteristic is shared by purines and pyrimidines?

• Both contain two heterocyclic rings with aromatic character.
• Both can form multiple non-covalent hydrogen bonds.
• Both exist in planar configurations with a hemiacetal linkage.
• Both exist as neutral zwitterions under cellular conditions.

Which characteristic is shared by both adenine and cytosine?

• Both contain one methyl group.
• Both are anomeric.
• Both contain one keto group.
• Both are heterocyclic.

On sequence analysis of a double stranded DNA, the results showed the content of cytosine, C was 20%. What is the amount of A and T put together?

• 20%
• 30%
• 50%
• 60%

What is the number of hydrogen bonds in helical B-DNA structure of 100 base pairs with 20 adenines and 10 thymines in one of the two strands?

• 200
• 230
• 270
• 300

In a DNA double helix:

• the individual strands are not helical.
• hydrogen bonds form between a purine and a pyrimidine base on the same strand.
• adenine on one strand is hydrogen­-bonded to thymine on the opposite strand.
• phosphodiester bonds are oriented toward the interior of the helix.
• the outside of the helix is neutral.

Mark the correct statements

• ATP is an example of a deoxynucleoside triphosphate .
• The most common ribonucleoside triphosphates have phosphate attached to the 5' carbon of the sugar moiety .
• An A/T base pair and a C/G base pair have about the same physical dimensions .
• If GGGGCCCC represents the sequence of bases in one strand of a double-stranded DNA then the complementary strand must have the sequence CCCCGGGG .
• The conformation of sugar in DNA is α-2'-deoxy-D-ribofuranose.

Which component is found in both adenosine and deoxycytidine?

• Both contain a purine.
• Both contain a 1,1’-N-glycosidic bond.
• Both contain a pyrimidine.
• Both contain a 3’-OH group.

Which property is found in nucleosides and nucleotides?

• Both contain a nitrogenous base, a pentose, and at least one phosphate group.
• Both contain a covalent phosphodister bond that is broken in strong acid.
• Both contain an anomeric carbon atom that is part of a β-N-glycosidic bond.
• Both contain a nitrogenous base that forms covalent H-bonds.

Polynucleotide is a polymer in which:

• the two ends are structurally equivalent.
• the monomeric units are joined together by phosphodiester bonds.
• there are at least 20 different kinds of monomers that can be used.
• the monomeric units are not subject to hydrolysis.
• purine and pyrimidine bases are the repeating units.