Molecular Biology – Core Vocabulary

Vocabulary flashcards summarizing essential molecular biology terms and definitions from the lecture notes.

Restriction endonuclease

An enzyme that recognizes specific 4–6 bp DNA sequences and cleaves the DNA at those sites, producing blunt or sticky ends for molecular manipulation.

Blunt end

A DNA fragment end produced by straight, even cleavage across both strands with no overhanging bases.

Sticky end

A DNA fragment end with short, single-stranded overhangs created by staggered cuts, enabling complementary annealing.

DNA ligase

The enzyme that covalently joins DNA fragments, efficiently sealing compatible sticky ends during cloning.

Isoschizomer

A pair of restriction enzymes that cut different recognition sequences yet generate identical overhangs.

Polynucleotide kinase (PNK)

An enzyme that transfers phosphate groups to 5′ DNA ends, used for low-activity DNA labeling.

Terminal transferase

A low-activity enzyme that adds nucleotides to 3′ DNA ends for labeling or tailing reactions.

Nick translation

A high-activity DNA-labeling method using DNA polymerase I and DNase I to incorporate labeled nucleotides at single-strand nicks.

Random priming

A high-activity DNA-labeling technique where random oligonucleotides prime DNA polymerase I to synthesize labeled strands.

Polymerase Chain Reaction (PCR)

A high-activity method employing Taq DNA polymerase to exponentially amplify specific DNA segments.

Coding DNA

Genomic regions transcribed and translated into proteins; <2 % of the human genome.

Junk DNA

Non-coding genomic sequences with functions not yet fully understood.

Allele

Different versions of a gene that vary slightly in sequence and can influence phenotype.

Exon

A protein-coding segment of a gene that remains in mature mRNA after splicing.

Intron

A non-coding sequence within a gene removed from pre-mRNA during splicing.

Human genome size

Approximately 3 300 Mb of DNA per haploid set.

PhiX174

The bacteriophage whose 5 375-nucleotide genome was the first sequenced (Sanger, 1977).

Nucleotide

The basic DNA/RNA building block composed of a phosphate, a pentose sugar, and a nitrogenous base.

A–T base pair

DNA pairing between adenine and thymine via two hydrogen bonds.

G–C base pair

DNA pairing between guanine and cytosine via three hydrogen bonds.

Uracil (U)

The RNA base that replaces thymine and pairs with adenine.

Central Dogma

The flow of genetic information: DNA → RNA → Protein.

RNA polymerase

The enzyme that synthesizes RNA from a DNA template during transcription.

Start codon (AUG)

The mRNA triplet that signals initiation of translation, coding for methionine.

Stop codons

mRNA triplets UAA, UAG, or UGA that terminate translation.

Transfer RNA (tRNA)

Adaptor molecule that delivers specific amino acids to the ribosome according to mRNA codons.

Primary protein structure

The linear sequence of amino acids in a polypeptide chain.

Secondary protein structure

Local folding patterns (α-helices, β-sheets) stabilized by hydrogen bonds.

Tertiary protein structure

Three-dimensional folding of a single polypeptide due to side-chain interactions.

Quaternary protein structure

Assembly of multiple polypeptide subunits into a functional protein complex.

Semi-conservative replication

DNA duplication mechanism where each daughter molecule retains one parental strand and synthesizes one new strand.

Restriction endonuclease

An enzyme originating from bacteria that recognizes specific 4–6 bp palindromic DNA sequences and cleaves the DNA at those precise sites. This cleavage produces either blunt ends (straight cuts) or sticky ends (single-stranded overhangs), which are crucial for subsequent molecular manipulation, particularly for inserting DNA fragments into vectors during cloning experiments.