Nucleic Acids: Structure and DNA/RNA Overview

Practice flashcards covering nucleic acid basics, nucleotide components, RNA vs DNA, backbone and bonds, base pairing, DNA structure, and the central dogma.

What are nucleic acids?

Polymers made of nucleotides; they are the biological polymers analogous to proteins being polymers of amino acids.

What are the three components of a nucleotide?

A phosphate group, a five-carbon sugar (pentose), and a nitrogenous base; both the phosphate and the base attach to the sugar.

What forms the sugar–phosphate backbone in nucleic acids?

Phosphodiester linkages joining the sugar of one nucleotide to the phosphate of the next.

What is a phosphodiester bond?

The covalent bond between a sugar’s phosphate and the next nucleotide’s sugar; a polar covalent bond.

What sugar is used in RNA?

Ribose, which has a hydroxyl group at the 2' position, making RNA more reactive.

What sugar is used in DNA?

Deoxyribose, which lacks the 2' hydroxyl, making DNA more stable.

Which nitrogenous bases are purines, and which are pyrimidines?

Purines: adenine (A) and guanine (G) with two rings; Pyrimidines: cytosine (C), thymine (T) in DNA, and uracil (U) in RNA.

Which bases pair with which in DNA?

A pairs with T (two hydrogen bonds); G pairs with C (three hydrogen bonds).

Which bases are unique to RNA and DNA?

Uracil is found in RNA; thymine is found in DNA.

What is meant by 5' and 3' ends in nucleic acids?

The 5' end has the phosphate attached to the 5' carbon of the sugar; the 3' end has the 3' hydroxyl that accepts the next nucleotide.

What is the significance of strand directionality and antiparallel orientation?

Nucleic acids are read 5' to 3'; the two strands run in opposite directions (antiparallel) in a double helix.

What stabilizes the DNA double helix?

Hydrogen bonds between complementary bases (A–T and G–C) and the antiparallel, complementary arrangement.

Who proposed the DNA double-helix and complementary base pairing?

Watson and Crick, with Rosalind Franklin (and Wilkins) contributing data, proposing the antiparallel double helix and base pairing.

What is the role of histone proteins?

Histones help compact and tightly pack DNA into chromatin in the nucleus, aiding in packaging during cell division.

What are the three levels of DNA structure mentioned?

Primary (sugar–phosphate backbone and sequence), Secondary (double helix with base-pair hydrogen bonds), and Tertiary (supercoiling/packing).

What is the central dogma described here?

DNA stores hereditary information; transcription to RNA; translation to protein; proteins perform cellular functions.

What is meant by a gene in this context?

A sequence of bases that encodes information to produce RNA and ultimately a protein.

How does complementary base pairing enable prediction of the other DNA strand?

Knowing one strand’s sequence allows deduction of the other strand using A↔T and G↔C base-pair rules.

What is the role of a phosphodiester bond in nucleic acids?

A covalent, polar bond that links sugars and phosphates between adjacent nucleotides, forming the backbone.

What happens during condensation in nucleic acid polymerization?

Removal of water allows nucleotides to join via phosphodiester bonds.

What analogy is used for the nitrogenous bases and genetic information?

Bases are like letters that form words (genes); their sequence encodes hereditary information.