Nucleic Acids, Protein Synthesis, and Molecular Genetics

Vocabulary practice flashcards covering nucleic acid structures, DNA replication, transcription, translation, mutations, biotechnology tools, viruses, and vaccine immunology.

Nuclein

The acidic, phosphorus-rich material isolated by Friedrich Miescher in 1869 from the nuclei of pus cells, which was later recognized as nucleic acid.

Nucleic Acids

Unbranched biopolymers composed of nucleotide monomers (such as DNA and RNA) responsible for storing, transmitting, and expressing genetic information in living cells.

Deoxyribonucleic Acid (DNA)

A double-stranded, helical nucleic acid containing 2-deoxy-D-ribose and the bases adenine, guanine, cytosine, and thymine, which stores and transmits genetic information across generations.

Ribonucleic Acid (RNA)

A typically single-stranded nucleic acid polymer containing D-ribose and the bases adenine, guanine, cytosine, and uracil that translates genetic instructions from DNA into proteins.

Nucleotide

The monomer building block of nucleic acids, consisting of three components: a nitrogen-containing base, a pentose sugar, and a phosphate group.

Pyrimidine

A single-ring, nitrogenous aromatic heterocyclic base found in nucleic acids; includes cytosine (C), thymine (T), and uracil (U).

Purine

A double-ring, nitrogen-containing heterocyclic base composed of fused six-membered and five-membered rings; includes adenine (A) and guanine (G).

Nucleoside

A molecular compound formed when a nitrogen atom of a nitrogenous base forms a $\beta\text{-N-glycosidic bond}$ to the $C1'$ anomeric carbon of a pentose sugar (base + sugar).

Phosphodiester Bond

The covalent ester linkage that connects the $3'\text{-OH}$ group of one sugar to the $5'\text{-phosphate}$ group of an adjacent sugar, forming the structural backbone of nucleic acids.

Complementary Base Pairs

Specific pairs of nitrogenous bases joined by hydrogen bonding in double-stranded DNA: adenine pairs with thymine via $2$ hydrogen bonds, and guanine pairs with cytosine via $3$ hydrogen bonds.

Histones

Proteins rich in basic amino acids that bind electrostatically to negatively charged acidic DNA to package and condense it into chromosomes.

Nucleosome

A repeating structural subunit of chromatin consisting of a section of double-stranded DNA wound around an octameric core of eight basic histone proteins.

Solenoid

A condensed $30\,\text{nm}$ chromatin fiber formed by the coiling of nucleosomes with six nucleosomes per turn.

Gene

A functional segment of a DNA molecule (typically $1{,}000$ to $2{,}000$ nucleotides long) that carries the necessary sequence information to synthesize a specific protein.

Ribosomal RNA (rRNA)

The most abundant type of cellular RNA, found in ribosomes, which serves as the physical site for protein synthesis.

Messenger RNA (mRNA)

The RNA molecule synthesized during transcription that carries genetic instructions from nuclear DNA out to cytoplasmic ribosomes for translation.

Transfer RNA (tRNA)

The smallest type of RNA ($70$ to $90$ nucleotides long) containing an anticodon loop and a $3'$ CCA acceptor stem that delivers specific amino acids to the ribosome during protein synthesis.

Semiconservative Replication

The mechanism of DNA synthesis in which each resulting double helix is composed of one intact conserved parental strand and one newly formed daughter strand.

Leading Strand

The newly synthesized DNA strand that is assembled continuously in the $5' \rightarrow 3'$ direction toward the advancing replication fork.

Lagging Strand

The newly synthesized DNA strand that is assembled discontinuously in short segments away from the replication fork in the $5' \rightarrow 3'$ direction.

Helicase

An enzyme that binds to a DNA strand and unwinds the double helix by disrupting hydrogen bonds between complementary base pairs.

Primase

An enzyme that synthesizes short RNA primers ($4$ to $15$ nucleotides) necessary to initiate complementary DNA strand synthesis.

DNA Polymerase

An enzyme that catalyzes the synthesis of a new DNA strand by joining incoming nucleoside triphosphates to the free $3'\text{-OH}$ group of a growing nucleic acid chain.

DNA Ligase

An enzyme that catalyzes the covalent joining of Okazaki fragments along the lagging strand during DNA replication.

Transcription

The enzymatic process wherein the base sequence of a DNA template strand is copied into a complementary single-stranded mRNA molecule by RNA polymerase.

Template Strand

The single strand of DNA that runs in the $3' \rightarrow 5'$ direction and is read by RNA polymerase to synthesize complementary RNA.

Coding Strand

The informational DNA strand that is complementary to the template strand and has the same sequence as the synthesized mRNA transcript (with thymine instead of uracil).

Genetic Code

The language of 64 nucleotide triplets (codons) in mRNA that specifies which of the 20 amino acids is incorporated during protein synthesis, along with start and stop signals.

Codon

A specific sequence of three consecutive nucleotides in an mRNA molecule that codes for a single amino acid or signals translation termination.

Anticodon

A triplet of nucleotides on a loop of a tRNA molecule that base-pairs with a complementary triplet codon on an mRNA strand.

Translation

The process occurring on ribosomes in which the nucleotide sequence of an mRNA molecule is decoded to assemble a polypeptide chain with a specific amino acid sequence.

Point Mutation

A gene mutation involving the substitution or replacement of a single base in a DNA sequence with a different base.

Frameshift Mutation

A mutation resulting from the insertion or deletion of one or more nucleotide bases in DNA, altering the triplet reading frame of all downstream codons.

Silent Mutation

A mutation that changes a nucleotide base in DNA but results in the same encoded amino acid, having a negligible effect on the organism.

Recombinant DNA

Synthetic DNA constructed in the laboratory by combining DNA sequences originating from two or more different biological sources.

Restriction Endonuclease

A bacterial enzyme, such as EcoRI, that cleaves double-stranded DNA at specific nucleotide recognition sequences, often generating staggered, single-stranded sticky ends.

Polymerase Chain Reaction (PCR)

A laboratory technique used to amplify a targeted DNA segment into millions of copies through repeating thermal cycles of strand denaturation, primer annealing, and extension by DNA polymerase.

DNA Fingerprinting

An analytical method of individual identification based on amplifying unique DNA regions by PCR, cutting them with restriction enzymes, and separating fragments by size using gel electrophoresis.

Retrovirus

An RNA virus (such as HIV) that replicates by synthesizing viral DNA from its RNA core via reverse transcription upon invading a host cell.

Reverse Transcriptase

A viral enzyme that catalyzes the synthesis of complementary DNA from an RNA template strand.

Adjuvant

A substance paired with an antigen in a vaccine to augment or enhance the magnitude of the host's immune response.

Innate Immunity

Early, non-specific immune defenses that respond immediately to an invading pathogen without providing pathogen-specific recognition or long-term immunological memory.

Neutralizing Antibodies

Specific adaptive immune proteins that bind to a pathogen and directly block it from entering or infecting host cells.

Antibody-Dependent Enhancement (ADE)

A phenomenon wherein pathogen-bound antibodies fail to neutralize the pathogen and instead facilitate viral entry into host cells like a Trojan horse, worsening the severity of the disease.