Transcription, Translation, and Bacterial Genetics

A set of vocabulary flashcards covering transcription, translation, ribosomal active sites, mutation types, and mechanisms of horizontal gene transfer in bacteria.

Template Strand

The strand of DNA that RNA polymerase physically reads in the $3'$ to $5'$ direction to synthesize a complementary messenger RNA (mRNA).

Nontemplate Strand

The DNA strand that is not read by RNA polymerase; also called the coding strand because its sequence matches the mRNA letter for letter (except for uracil replacing thymine).

RNA Polymerase

The enzyme that binds to a promoter at the beginning of a gene and moves along the template strand to produce mRNA.

tRNA (Transfer RNA)

A single-stranded RNA molecule that folds into stem structures with a T-like shape and transfers specific amino acids to the growing peptide chain during translation.

AUG

The unique start codon that signals the ribosome to begin making a protein and codes for the amino acid methionine.

Stop Codon

An mRNA sequence (such as UGA) that does not carry an amino acid but signals the ribosome that the end of the protein has been reached, causing the complex to disassemble.

Opal, Amber, and Ochre

The three unique names associated with the specific stop codons that terminate translation.

A Site (Aminoacyl Site)

The region of the ribosome where charged tRNAs carrying amino acids enter to match their anticodon with the mRNA codon.

P Site (Peptidyl Site)

The region of the ribosome that holds the growing peptide chain and where peptide bonds are formed between amino acids.

E Site (Exit Site)

The region of the ribosome where uncharged tRNAs exit after transferring their amino acid to the peptide chain.

Initiation

The first step of translation in which the initiator tRNA charged with methionine, the mRNA, and the small and large ribosomal subunits assemble together.

Elongation

The stage of translation where tRNAs continuously enter the A site, form peptide bonds with the growing polypeptide chain, and shift through the ribosome.

Termination

The final stage of translation triggered by a stop codon, causing the complete protein to release, the ribosome to disassemble, and the mRNA to be degraded.

Frameshift Mutation

A mutation caused by insertions or deletions of nucleotides that alters the triplet codon reading frame, often yielding a truncated, nonfunctional protein.

Silent Mutation

A base substitution that alters a nucleotide in the DNA but results in the same amino acid due to codon redundancy, leaving the resulting protein unchanged.

Missense Mutation

A base substitution where a single nucleotide change causes a different amino acid to be incorporated into the protein.

Nonsense Mutation

A base substitution that changes an amino acid codon into a stop codon, prematurely truncating the protein.

Conjugation

A mechanism of horizontal gene transfer in bacteria where a donor cell uses a pilus to transfer an F plasmid to an $F^-$ recipient cell.

Transformation

A mechanism of horizontal gene transfer in which competent bacterial cells take up free, naked DNA directly from their surrounding environment.

Transduction

A mechanism of horizontal gene transfer where bacterial DNA is transferred from one host bacterium to another via a bacteriophage virus.

Bacteriophages

Viruses that specifically infect bacteria and can accidentally package and transfer bacterial chromosomal DNA during viral infection.