Nucleic Acids and Nucleotides Vocabulary

Vocabulary flashcards covering the key terms, structural components, and properties of nucleic acids, nucleotides, DNA helices, and RNA structures.

Nucleotide

A molecule composed of three characteristic components: a nitrogenous base, a pentose sugar, and one or more phosphate groups.

Nucleoside

A molecule consisting of a nitrogenous base attached to a pentose sugar, lacking a phosphate group.

Purine

A heterocyclic nitrogenous base structure containing two fused rings, represented in nucleic acids primarily by adenine (A) and guanine (G).

Pyrimidine

A heterocyclic nitrogenous base structure containing a single six-membered ring, represented by cytosine (C), thymine (T), and uracil (U).

2-deoxy-D-ribose

The pentose sugar present in DNA nucleotides that lacks a hydroxyl group ($-\text{OH}$) at the $2'$ position, having a hydrogen atom ($-\text{H}$) instead.

D-ribose

The pentose sugar found in RNA nucleotides that possesses a hydroxyl group ($-\text{OH}$) at the $2'$ carbon.

Phosphodiester linkage

The covalent linkage connecting successive nucleotides in DNA and RNA, joining the $5'\text{-phosphate group}$ of one nucleotide to the $3'\text{-hydroxyl group}$ of the next.

Base Stacking

Hydrophobic interactions, van der Waals forces, and dipole-dipole interactions between neighboring nitrogenous bases that minimize water contact and stabilize the three-dimensional structure of nucleic acids.

Oligonucleotide

A short nucleic acid polymer consisting of $50$ or fewer nucleotides.

Polynucleotide

A longer nucleic acid polymer containing more than $50$ nucleotides.

Chargaff's Rules

The rule governing double-stranded DNA base composition, stating that the number of adenine residues equals thymine ($A=T$) and guanine residues equals cytosine ($G=C$).

B-DNA

The standard right-handed double-helical structure of DNA under physiological conditions, featuring a diameter of $\approx 20\,\text{\AA}$, $10\,\text{base pairs}$ per helical turn, a pitch of $34\,\text{\AA}$, and a rise of $3.4\,\text{\AA}$ per base pair.

A-DNA

A wider, flatter right-handed DNA double helix formed when relative humidity is reduced to $75\%$, featuring $11.6\,\text{base pairs}$ per turn, base pairs tilted $20^\circ$ to the helix axis, and a central axial hole.

Z-DNA

A left-handed double helix with a diameter of $\approx 18\,\text{\AA}$, $12\,\text{base pairs}$ per turn ($6\,\text{dimers}$), a pitch of $44\,\text{\AA}$, a deep minor groove, and a zigzag backbone path.

UUCG Tetraloop

An exceptionally stable RNA stem-loop sequence whose stability is enhanced by base-stacking interactions within the loop.

G:U Base Pair

A non-Watson-Crick base pair commonly found in rRNA that enhances the capacity of RNA for self-complementarity.

Monocistronic mRNA

An mRNA transcript that carries the genetic code for only one single polypeptide chain, characteristic of most eukaryotic mRNAs.

Polycistronic mRNA

An mRNA transcript that codes for two or more different polypeptide chains, commonly found in bacteria and archaea.