Nucleic Acids and Molecular Biology

Comprehensive vocabulary flashcards covering the central dogma, DNA and RNA structure, mutations, packaging, and specific types of nucleic acids from the lecture notes.

Replication

The process of DNA synthesis to copy or duplicate the genetic information.

Transcription

The process that copies genetic information from DNA into messenger RNA (mRNA).

Translation

The process where the genetic code of the mRNA is decoded into a linear amino acid sequence to form protein.

Nucleotide

A molecule composed of a $5 \text{-carbon}$ sugar, a nitrogenous base, and one, two, or three phosphoryl groups.

Purine

A class of nitrogenous bases that includes adenine and guanine, found in both DNA and RNA.

Pyrimidine

A class of nitrogenous bases that includes cytosine (DNA and RNA), thymine (DNA only), and uracil (RNA only).

B-DNA

The normal form of DNA found in cells, characterized as a double-stranded right-handed helix with $10.4 \text{ bp/turn}$, a diameter of $2.0 \text{ nm}$, and $3' \text{-} 5'$ phosphodiester bonds.

Stacking interactions

Forces that stabilize the double helix where aromatic base pairs form van der Waals contacts between each other.

Electrostatic interactions

Stabilizing forces in DNA where cations, particularly $\text{Mg}^{2+}$, reduce the repulsion between negative phosphodiester groups.

Transition Mutations

Mutations that arise from incorrect base pairing due to the tautomers of purine bases.

Alkylating agents

External factors that cause mutations by adding alkyl groups, such as methyl groups, to bases like adenine and guanine.

Intercalating agents

Planar molecules that cause mutations by inserting themselves between the DNA strands.

A-DNA

A partially dehydrated form of DNA with base pairs tilted at $20^{\text{o}}$, containing $11 \text{ bp/turn}$ and a diameter of $2.6 \text{ nm}$.

Z-DNA

A left-handed helix with a zigzag conformation containing $12 \text{ bp/turn}$, typically observed in segments with alternating purine and pyrimidine bases like CGCGCG.

H-DNA

A triple helix structure formed under low pH consisting of a long segment of a polypurine strand $\text{H-bonded}$ to a polypyrimidine strand.

Negatively supercoiled DNA

Underwound DNA where the duplex is twisted opposite to the direction of the double helix, often forming an interwound supercoil.

Polyamines

Polycationic molecules such as spermidine and spermine that assist in attaining the compressed DNA structure in prokaryotes.

Centromeres

Constricted regions on a chromosome with specific $\text{AT-rich}$ DNA sequences that attach to spindle fibers during cell division.

Telomeres

$\text{CCCA}$ repetitive regions at the ends of chromosomes that prevent the unraveling of DNA.

Histones

Small basic proteins rich in lysine, categorized into five major classes: $H1$, $H2A$, $H2B$, $H3$, and $H4$.

Nucleosome

A "bead" structure composed of DNA coiled around an octameric histone core containing two copies each of $H2A$, $H2B$, $H3$, and $H4$.

Linker DNA

A short segment of DNA that connects adjacent nucleosomes.

Introns

Noncoding sequences interspersed between gene coding sequences in eukaryotic DNA.

Exons

Gene coding sequences in eukaryotic DNA.

Ribosomal RNA (rRNA)

The most abundant form of RNA which makes up the ribosomes, the site of protein synthesis.

Prokaryotic Ribosome

A $70S$ ribosome consisting of $50S$ and $30S$ subunits.

Transfer RNA (tRNA)

An RNA molecule with a cloverleaf secondary structure that carries activated amino acids to the ribosome.

Polycistronic mRNA

Prokaryotic mRNA that contains several genes on one messenger strand and is translated directly after synthesis.

Monocistronic mRNA

Eukaryotic mRNA that contains the coding sequence for a single protein and undergoes extensive processing like capping and splicing.

Heterogenous nuclear RNA (hnRNA)

The primary transcripts of DNA that serve as precursors to mRNA.

Small nuclear RNA (snRNA)

RNA complexed with proteins to form small nuclear ribonucleoprotein particles (snRNP) involved in splicing.

RNA splicing

The post-transcriptional process involving the removal of introns (non-protein coding portions) from the primary transcript.