Polynucleotides and DNA Structure

Vocabulary flashcards covering the components of nucleotides, phosphodiester bonds, directionality, and the structural features of DNA.

Nucleotide

The monomer of a polynucleotide or nucleic acid, composed of a phosphate group, a five-carbon pentose sugar, and a nitrogenous base.

Nucleoside

The molecular component of a nucleotide consisting of only a pentose sugar and a nitrogenous base, without a phosphate group.

Pyrimidines

A family of nitrogenous bases characterized by a single ring structure, which includes Cytosine (C), Thymine (T, found in DNA), and Uracil (U, found in RNA).

Purines

A family of nitrogenous bases characterized by a double ring structure, consisting of Adenine (A) and Guanine (G).

Deoxyribose

The pentose sugar present in DNA nucleotides, characterized by having an $-H$ atom instead of an $-OH$ group attached to the $2'$ carbon.

Ribose

The pentose sugar present in RNA nucleotides, which possesses a hydroxyl group ($-OH$) attached to the $2'$ carbon.

$5'$ end

The directional terminal end of a nucleic acid strand that carries a 'free' (unbound) phosphate group.

$3'$ end

The directional terminal end of a nucleic acid strand that carries a 'free' (unbound) hydroxyl group.

Directionality of nucleic acids

The property describing how nucleic acid strands are oriented, synthesized, and written from the $5'$ end to the $3'$ end.

Phosphodiester bond

A covalent linkage formed by a condensation reaction (releasing $H_2O$) that connects the $3'$ carbon of one nucleotide to the $5'$ carbon of the next through its phosphate group to link nucleotides within a strand.

Antiparallel strands

The structural arrangement of the two complementary strands in a DNA molecule, oriented in opposite directions ($5'$ to $3'$ versus $3'$ to $5'$).

Base pairs

Complementary nitrogenous bases from opposing strands of DNA that pair and are held together by hydrogen bonds.

Adenine and Thymine pairing

The specific complementary base pairing between Adenine (A) and Thymine (T) held together by $2$ hydrogen bonds in DNA.

Guanine and Cytosine pairing

The specific complementary base pairing between Guanine (G) and Cytosine (C) held together by $3$ hydrogen bonds in DNA.

DNA helical dimensions

Structural dimensions of the DNA double helix featuring a diameter of $1\text{ nm}$, a distance of $0.34\text{ nm}$ between adjacent base pairs, and a helical turn repeat distance of $3.4\text{ nm}$.