DNA Transcription and Translation: Key Concepts for Biology

Promoter

Region of DNA where RNA polymerase binds to start transcription.

Transcription Unit

Section of DNA that is transcribed into RNA.

Start Point

The first nucleotide where RNA synthesis begins.

RNA Polymerase

Enzyme that builds RNA by reading the DNA template.

5′ End (DNA/RNA)

The "beginning" of a nucleic acid strand; direction RNA is synthesized toward.

3′ End (DNA/RNA)

The "end" of a nucleic acid strand; RNA polymerase reads the template 3′→5′.

Prokaryotic Initiation

RNA polymerase binds directly to the promoter and starts transcription without extra proteins.

TATA Box

A promoter sequence found in many eukaryotic genes.

Transcription Factors

Proteins that help RNA polymerase bind the promoter.

RNA Polymerase II

Enzyme that transcribes mRNA in eukaryotes.

Template Strand (DNA)

The DNA strand used as a template to build RNA.

RNA Transcript

The newly forming strand of RNA.

Elongation (Transcription)

RNA polymerase moves downstream, adding RNA nucleotides to extend the RNA strand.

Nontemplate Strand (DNA)

The DNA strand not used for RNA synthesis.

Direction of Transcription

RNA is always built 5′ → 3′.

Prokaryotic Termination

RNA polymerase reaches a terminator sequence and releases the RNA molecule.

Polyadenylation Signal (AAUAAA)

Sequence in RNA that signals cutting and termination.

5′ Cap

Modified G nucleotide added to the 5′ end of eukaryotic mRNA.

5′ UTR / 3′ UTR

Regulatory regions before and after the coding sequence.

Start Codon (AUG)

The first codon used to begin translation.

Stop Codon (UAA, UAG, UGA)

Codons that signal the end of translation.

Poly-A Tail

A long chain of adenines added to the 3′ end of eukaryotic mRNA.

Exons

Coding regions that remain in the final mRNA.

Introns

Non-coding regions removed during splicing.

snRNA

Small nuclear RNA molecules that help with splicing.

snRNPs

Protein-RNA complexes that form part of the spliceosome.

Spliceosome

Complex that removes introns and joins exons.

Aminoacyl-tRNA Synthetase

Enzyme that attaches an amino acid to a tRNA.

ATP (in tRNA charging)

Energy source used to attach amino acids to tRNA.

Aminoacyl-tRNA (Charged tRNA)

A tRNA carrying its specific amino acid.

Translation Initiation

The ribosome assembles on mRNA, and the initiator tRNA binds the start codon.

Stop Codon

mRNA signal that causes translation to end.

Release Factor

Protein that binds the stop codon and frees the polypeptide.

Free Polypeptide

The finished amino acid chain (protein).

GTP → GDP (Termination)

Energy used to release the ribosome and complete translation.