Nucleic Acids Lecture Flashcards

A set of vocabulary flashcards covering the chemical structure, organization, and types of nucleic acids (DNA and RNA) based on the lecture notes.

3′ → 5′-phosphodiester bond

The specific covalent linkage that joins mononucleotides to form polynucleotides in both DNA and RNA.

Nucleoside

A structure consisting of a ribose or deoxyribose sugar linked covalently via an N-glycosidic bond at C-1 to the N-9 of a purine or the N-1 of a pyrimidine.

Nucleotide

A molecule consisting of a nitrogenous base, a sugar, and at least one phosphate group, typically phosphorylated at the 5'-carbon of the ribose.

Purines

A category of nitrogenous bases that includes Adenine and Guanine.

Pyrimidines

A category of nitrogenous bases that includes Cytosine, Thymine (found in DNA), and Uracil (found in RNA).

ATP (Adenosine 5'-triphosphate)

A nucleotide that serves as a primary energy carrier and part of many coenzymes.

Watson and Crick Model

A structural model describing DNA as two antiparallel helical polynucleotide chains coiled around a common axis to form a right-handed double helix.

Complementary Base Pairing

The specific pairing in DNA where Adenine binds with Thymine via two hydrogen bonds ($A=T$) and Guanine binds with Cytosine via three hydrogen bonds ($G \text{≡} C$).

Chargaff's Rule

The finding that the amount of purines equals the amount of pyrimidines in DNA ($G+A=C+T$).

B-DNA

The structural form of DNA that prevails under physiologic conditions of low ionic strength and high hydration.

Nucleosome

A unique DNA-histone complex formed by DNA wrapped around an octamer of highly positively charged histone proteins.

Histones

Basic proteins rich in lysine and arginine whose positive charges interact with the negative charge of DNA to permit tight packing.

Chromatin

The chromosomal material composed of DNA, RNA, and protein complexes (primarily histones).

Mitochondrial DNA (mtDNA)

Small circular double-stranded DNA found in mitochondria, transmitted via maternal inheritance, constituting approximately $1\%$ of cellular DNA.

DNA Denaturation

The process of separating the two strands of the DNA double helix, which can be induced by high temperature or extremes of pH.

Reannealing (Hybridization)

The process where separated complementary DNA strands reform base pairs as they cool.

Transcription

The process by which RNA is synthesized from a DNA template.

Messenger RNA (mRNA)

A type of RNA ($2–5\%$ of total) that carries genetic information from DNA to the cytosol, characterized by a 5'-cap of 7-methyl guanine and a 3' poly-A tail.

Transfer RNA (tRNA)

Molecules consisting of $74–95$ nucleotides that act as adaptors for transferring genetic information into amino acids during translation.

Ribosomal RNA (rRNA)

The most abundant type of RNA ($80\%$) that associates with proteins to form components of the ribosome.

Small nuclear RNA (snRNA)

A type of RNA with enzymatic function (ribozyme) that plays a role in the maturation of mRNA.

MicroRNA (miRNA)

RNA molecules representing less than $1\%$ of total cellular RNA involved in the regulation of gene expression.