Nucleic acids Knowledge-Based Download PDF

Questions

1. 1.

   In a linear polynucleotide chain, which chemical groups are present at the unlinked termini to define the 5' end and the 3' end, respectively?

   • A) An amino group at the 5' end and a carboxyl group at the 3' end
   • B) A hydroxyl group at the 5' end and a phosphate group at the 3' end
   • C) A nitrogenous base at the 5' end and a pentose sugar at the 3' end
   • D) A phosphate group at the 5' end and a hydroxyl group at the 3' end
2. 2.

   Which structural feature distinguishes purine nitrogenous bases from pyrimidine nitrogenous bases found in cellular nucleic acids?

   • A) Purines contain a single six-membered ring, whereas pyrimidines consist of two fused rings.
   • B) Purines possess a double-ring structure composed of a six-membered ring fused to a five-membered ring, whereas pyrimidines possess a single six-membered ring.
   • C) Purines contain nitrogen atoms only in their side chains, whereas pyrimidines contain nitrogen atoms within their ring skeletons.
   • D) Purines occur exclusively in deoxyribonucleic acid, whereas pyrimidines occur exclusively in ribonucleic acid.
3. 3.

   Which of the following statements accurately describes the hydrogen bonding between complementary nitrogenous base pairs in double-stranded DNA?

   • A) Adenine pairs with thymine via three hydrogen bonds, while guanine pairs with cytosine via two hydrogen bonds.
   • B) Adenine pairs with thymine via two hydrogen bonds, while guanine pairs with cytosine via three hydrogen bonds.
   • C) Adenine pairs with cytosine via two hydrogen bonds, while guanine pairs with thymine via three hydrogen bonds.
   • D) Adenine pairs with uracil via three hydrogen bonds, while guanine pairs with cytosine via two hydrogen bonds.
4. 4.

   Which type of chemical bond covalently links adjacent nucleotides in a single polynucleotide strand to form the sugar-phosphate backbone?

   • A) Hydrogen bonds formed between opposing nitrogenous bases
   • B) Peptide bonds connecting amino and carboxyl functional groups
   • C) Glycosidic bonds directly joining adjacent pentose sugars
   • D) Phosphodiester bonds linking a 3' hydroxyl group to a 5' phosphate group
5. 5.

   Which of the following statements correctly describes the components of a nucleotide incorporated into ribonucleic acid (RNA)?

   • A) It consists of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases, which include thymine.
   • B) It consists of a ribose sugar, an amino acid, and one of four nitrogenous bases, which include uracil.
   • C) It consists of a ribose sugar, a phosphate group, and one of four nitrogenous bases: adenine, guanine, cytosine, or uracil.
   • D) It consists of a deoxyribose sugar, three phosphate groups, and one of four nitrogenous bases, which exclude cytosine.