Molecular Genetics – Lectures 1-5 (Central Dogma, Transcription, Translation, Replication, Mutation)

Vocabulary flashcards covering core terms from ANU Molecular Genetics lectures on DNA, transcription, translation, replication and mutation.

Nucleic Acid

Polymer of nucleotides that stores and transmits genetic information (DNA or RNA).

Chromosome

Condensed chromatin structure of DNA and proteins formed for cell division.

Translation

Process that converts mRNA information into a polypeptide on a ribosome.

Transcription

Synthesis of an RNA strand complementary to a DNA template by RNA polymerase.

Central Dogma

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

Griffith’s Experiment

1928 study showing a ‘transforming principle’ that converted non-virulent R bacteria into virulent S form.

Transforming Principle

Heritable material in dead S cells that altered living R cells; later identified as DNA.

Avery–MacLeod–McCarty Experiment

1944 work demonstrating DNA is the transforming principle by destroying DNA with nuclease and halting transformation.

Hershey–Chase Experiment

1952 bacteriophage study using 32P-DNA and 35S-protein to show DNA, not protein, enters infected cells.

Chargaff’s Rules

In DNA, amount of A equals T and G equals C; base composition varies by species.

Nucleotide Monophosphate

DNA/RNA building block consisting of a base, a sugar, and one phosphate group.

Phosphodiester Bond

Covalent linkage joining nucleotides in the sugar-phosphate backbone of nucleic acids.

Antiparallel

Orientation of the two complementary DNA strands running 5′→3′ and 3′→5′.

Purine

Double-ring nitrogenous base (adenine or guanine).

Pyrimidine

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

Genotype

Complete genetic makeup of an organism.

Phenotype

Observable traits or properties produced by genotype–environment interaction.

Beadle & Tatum Experiment

1941 Neurospora study establishing ‘one gene–one enzyme’ by isolating metabolic mutants.

Prototroph

Organism able to synthesize all required organic molecules from minimal medium.

Autotroph (in genetics)

Mutant strain requiring added nutrients because it lost a biosynthetic ability.

Tyrosinase

Enzyme in melanin synthesis; loss causes albinism.

MC1R

Melanocortin-1 receptor; reduced activity shifts pigment toward red pheomelanin.

DNA vs RNA

DNA: deoxyribose, A-T, double stranded, stable. RNA: ribose, A-U, single stranded, transient.

mRNA

Messenger RNA copy of a gene used as template for protein synthesis.

RNA Polymerase II

Eukaryotic enzyme that transcribes mRNA from DNA templates.

Promoter

DNA sequence where RNA polymerase and transcription factors assemble to start transcription.

Transcription Factor

Protein that binds DNA and helps recruit RNA polymerase to promoters.

Codon

Triplet of RNA bases that specifies one amino acid or stop signal.

Genetic Code

Set of rules linking 64 codons to 20 amino acids; degenerate, non-overlapping, nearly universal.

Start Codon (AUG)

Codon that begins translation and encodes methionine.

Stop Codon

UAA, UAG, or UGA sequence that terminates translation.

tRNA

Adaptor RNA carrying a specific amino acid and an anticodon that pairs with mRNA codons.

rRNA

Ribosomal RNA; structural and catalytic component of ribosomes.

Ribosome

RNA–protein complex with A, P, and E sites that catalyzes protein synthesis.

Open Reading Frame (ORF)

Continuous stretch of codons beginning with AUG and ending with a stop codon.

Origin of Replication

Specific DNA sequence where replication begins, forming ‘bubbles’ in S phase.

Semi-Conservative Replication

Mechanism where each daughter DNA has one parental and one new strand (Meselson–Stahl).

DNA Polymerase III

Main E. coli enzyme that extends DNA strands 5′→3′ and proofreads 3′→5′.

DNA Polymerase I

Enzyme that replaces RNA primers with DNA on the lagging strand.

Primase

RNA polymerase that synthesizes short RNA primers to initiate DNA synthesis.

Helicase

Enzyme that unwinds the DNA double helix by breaking hydrogen bonds.

Ligase

Enzyme sealing nicks between Okazaki fragments on the lagging strand.

Leading Strand

DNA strand synthesized continuously toward the replication fork.

Lagging Strand

Strand synthesized discontinuously as Okazaki fragments away from the fork.

Okazaki Fragment

Short DNA segment produced during lagging-strand replication.

Proofreading

Exonuclease activity of DNA polymerase that removes misincorporated nucleotides.

Point Mutation

Single-nucleotide change; can be silent, missense, or nonsense.

Silent Mutation

Base change that does not alter amino acid sequence.

Missense Mutation

Point mutation that replaces one amino acid with another in a protein.

Nonsense Mutation

Point mutation converting an amino acid codon into a stop codon.

Frameshift Mutation

Insertion or deletion not in multiples of three that shifts the reading frame.

Molecular Clock

Concept that neutral mutations accumulate at an approximately constant rate useful for dating divergence events.