Protein Synthesis & DNA Mutations – Key Vocabulary

Vocabulary flashcards covering essential terms from the lecture on protein synthesis (transcription, RNA processing, translation) and DNA mutations.

DNA

Double-stranded deoxyribonucleic acid that stores hereditary information inside the nucleus and condenses into chromosomes.

Chromosome

Tightly packed DNA molecule containing many genes within a eukaryotic nucleus.

Gene

A specific DNA sequence that encodes a single protein.

Genome

All of the genetic information contained in an organism’s DNA.

Central Dogma

The flow of genetic information: DNA → RNA → Protein (transcription, RNA processing, translation).

Transcription

Process in which RNA polymerase copies DNA into a complementary RNA strand. Nucleus

RNA Processing

Modification of pre-mRNA (5′ cap, 3′ poly-A tail, intron removal) to produce mature mRNA.

Translation

Decoding of mRNA by ribosomes to build a polypeptide chain (protein). Cytoplasm

mRNA (Messenger RNA)

RNA copy of a gene that carries the code from nucleus to ribosome.

tRNA (Transfer RNA)

Adapter molecule that delivers specific amino acids to the ribosome using its anticodon.

rRNA (Ribosomal RNA)

RNA component of ribosomes that helps catalyze peptide-bond formation.

Initiation (Transcription)

Stage where transcription machinery assembles at the promoter and DNA unwinds.

Elongation (Transcription)

RNA polymerase adds complementary RNA nucleotides in the 5′→3′ direction.

Termination (Transcription)

RNA polymerase recognizes a termination sequence and releases the RNA transcript.

Intron

Non-coding intervening sequence removed from pre-mRNA during processing.

Exon

Expressed coding sequence retained in mature mRNA.

Spliceosome

Enzyme complex that excises introns and ligates exons together.

5′ Cap

Modified guanine nucleotide added to the 5′ end of mRNA to aid ribosome binding.

Poly-A Tail

Series of ~150 adenines added to 3′ end of mRNA to protect against degradation.

Codon

Sequence of three mRNA nucleotides that specifies one amino acid or a stop signal.

Anticodon

Complementary three-base sequence on tRNA that pairs with an mRNA codon.

Start Codon

AUG; signals initiation of translation and codes for methionine.

Stop Codons

UAA, UAG, UGA; signal termination of translation.

Ribosome

Ribonucleoprotein complex with A, P, and E sites that coordinates translation.

Initiation (Translation)

Small ribosomal subunit, mRNA, and initiator tRNA assemble; large subunit joins.

Elongation (Translation)

tRNAs sequentially deliver amino acids; peptide bonds form and ribosome translocates.

Termination (Translation)

Release factor binds stop codon; polypeptide and ribosomal subunits are released.

Peptide Bond

Covalent bond linking amino acids during protein synthesis.

Translocation

Movement of ribosome along mRNA shifting tRNA from A to P to E sites.

Polypeptide

Linear chain of amino acids that folds into a functional protein.

Point Mutation

Single base substitution in DNA; can be silent, missense, or nonsense.

Silent Mutation

Base change that codes for the same amino acid; no change in protein function.

Missense Mutation

Base substitution that changes one amino acid in the protein sequence.

Nonsense Mutation

Base change that converts a codon into a premature stop codon.

Frameshift Mutation

Insertion or deletion of nucleotides that alters the reading frame of mRNA.

Sickle-Cell Mutation

Non-conservative missense in hemoglobin causing sickle-cell disease; heterozygotes resist malaria.

Mutagen

Agent (chemical, radiation) that increases mutation rate in DNA.

Thymine Dimer

Covalent linkage of adjacent thymines caused by UV light, leading to replication errors.

Ames Test

Bacterial assay that detects mutagenic chemicals by reversal of a histidine auxotrophy.

Somatic Mutation

DNA change in non-reproductive cells; not inherited but can cause cancer.

Germ-Line Mutation

DNA change in gametes; heritable and can affect offspring phenotype.

Teratology

Study of congenital malformations and factors causing birth defects.