Structure of DNA Practice Flashcards

Flashcards covering the molecular structure, components, and conformational variations of DNA and RNA based on the lecture transcript.

Genome

The hereditary basis of every living organism, consisting of a long sequence of DNA that provides the complete set of hereditary information; it includes chromosomal, plasmid, and organellar DNA.

Nucleotide

The basic building block of nucleic acids consisting of three components: a nitrogenous base, a pentose sugar, and one or more phosphates.

Nucleoside

A structure consisting of a nitrogenous base linked to the $1'$ carbon of a pentose sugar by a glycosidic bond.

2' deoxyribose

The specific pentose sugar found in DNA, which differs from ribose by the absence of a hydroxyl group at the $2'$ carbon.

Ribose

The pentose sugar found in RNA that contains a hydroxyl ($-OH$) group on the $2'$ carbon of the pentose ring.

5'–3' phosphodiester linkages

The bonds that form the sugar–phosphate backbone of a polynucleotide by linking the $5'$ carbon of one pentose ring to the $3'$ carbon of the next via a phosphate group.

Purine

A type of nitrogenous base with a double-ring structure; examples include adenine ($A$) and guanine ($G$).

Pyrimidine

A type of nitrogenous base with a single-ring structure; examples include cytosine ($C$), thymine ($T$), and uracil ($U$).

Uracil ($U$)

The pyrimidine found in RNA instead of thymine, which lacks a methyl group at position $C5$ compared to thymine.

Complementary Base Pairing

The specific hydrogen bonding between nitrogenous bases where $G$ forms three bonds with $C$, and $A$ forms two bonds with $T$.

Antiparallel

The arrangement in the DNA double helix where the two polynucleotide chains run in opposite directions, one in the $5'$ to $3'$ direction and the other in the $3'$ to $5'$ direction.

B-DNA

The standard 'right-handed' double helix model where turns run clockwise and each base pair is rotated about $36^{\circ}$ relative to the next, resulting in approximately $10$ base pairs per complete turn.

Major Groove

The larger of the two twisting indentations in the DNA double helix, measuring about $22\,\text{Å}$ ($2.2\,\text{nm}$) across.

Minor Groove

The smaller of the two twisting indentations in the DNA double helix, measuring about $12\,\text{Å}$ ($1.2\,\text{nm}$) across.

A-form DNA

A right-handed helical structure of DNA observed when it is dehydrated; it is shorter and thicker than the standard B-form.

Z-DNA

A left-handed DNA helix named for its 'zig-zag' backbone pattern; it is longer and narrower than the B-form.

Overwound DNA

A state of the DNA double helix where it contains more base pairs per turn than the standard average structure.

Underwound DNA

A state of the DNA double helix where it contains fewer base pairs per turn than the standard average structure.