Level 2 Bio: Gene Expression

Vocabulary flashcards covering key terms from gene expression, DNA/RNA structure, nucleotides, and protein structure for AS91156.

Gene Expression

The process by which the information encoded in a gene is used to direct the synthesis of a protein or functional RNA.

Gene

A length of DNA (100–2,000,000 base pairs) that codes for one protein; humans have ~25,000.

Chromosome

A package of DNA containing thousands of genes; human cells carry two copies of each chromosome.

Genome

The complete set of genes or genetic material present in a cell or organism.

Nucleus

Membrane-bound organelle in eukaryotes where genetic information (DNA) is stored.

DNA (Deoxyribonucleic Acid)

Double-stranded, helical nucleic acid that stores and transmits genetic information.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid that helps make proteins; contains ribose and bases A, U, C, G.

Nucleotide

The monomer of nucleic acids, consisting of a nitrogenous base, a pentose sugar, and a phosphate group.

Nitrogenous Base

Component of a nucleotide; in DNA: A, T, C, G; in RNA: A, U, C, G.

Pentose Sugar

Five-carbon sugar in nucleotides; deoxyribose in DNA, ribose in RNA.

Phosphate Group

Part of a nucleotide that links sugars of adjacent nucleotides, forming the nucleic-acid backbone.

Complementary Base Pairing

Specific hydrogen bonding of A with T (or U) and C with G in nucleic acids.

Purine

Double-ring nitrogenous base (adenine or guanine).

Pyrimidine

Single-ring nitrogenous base (cytosine, thymine, or uracil).

Monomer

A small molecule that can join others to form a polymer.

Polymer

A large molecule made of repeating monomers; DNA and RNA are nucleic-acid polymers.

Polynucleotide

A chain of many nucleotides linked together, forming DNA or RNA strands.

Double Helix

The twisted-ladder shape of double-stranded DNA.

Amino Acid

Building block of proteins; contains an alpha carbon, amino group, carboxyl group, and variable R-group.

Peptide Bond

Covalent bond joining amino acids in a protein backbone.

Protein

Polymer of amino acids that performs structural, enzymatic, transport, hormonal, and immune functions.

Primary Structure

Linear sequence of amino acids in a polypeptide held by peptide bonds.

Secondary Structure

Local folding of a polypeptide into α-helices or β-pleated sheets via hydrogen bonds.

α-Helix

Spiral secondary-structure motif stabilized by hydrogen bonds (e.g., in keratin).

β-Pleated Sheet

Folded secondary-structure motif forming sheets (e.g., in silk).

Tertiary Structure

Overall 3-D shape of a polypeptide stabilized by hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions.

Disulfide Bridge

Covalent S–S bond between two cysteine residues, stabilizing tertiary protein structure.

Hydrophobic Interaction

Non-polar side chains clustering away from water, aiding protein folding.

Quaternary Structure

Assembly of two or more polypeptide chains into a functional protein.

Hemoglobin

Quaternary protein with four subunits that transports oxygen in blood.

DNA Polymerase

Multi-subunit enzyme involved in DNA replication; exhibits quaternary structure.

Transcription

Process in which DNA is transcribed into messenger RNA (mRNA).

Translation

Process in which mRNA is decoded to synthesize a protein at the ribosome.