• 12 parts
  • Checked October 2026

Bacterial Gene Structure Diagram

One bacterial gene from promoter to terminator, and the mRNA made from it, end to end.

Bacterial Gene Structure Diagram

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1 2 3 4 5 6 7 8 9 10 11 12
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Write the name of each numbered part.Answer key

  1. Promoter
  2. −35 sequence
  3. −10 sequence (Pribnow box)
  4. Transcription start site
  5. Terminator
  6. mRNA
  7. Ribosome-binding site (Shine-Dalgarno sequence)
  8. Start codon
  9. Coding sequence
  10. Stop codon
  11. 5′ untranslated region
  12. 3′ untranslated region

Drawn for this site on 2026-10-03 by script from a table of positions. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: RNA polymerase at work

All 12 parts on the diagram

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The gene on the DNA 6

  1. Promoter RNA polymerase binds here to start transcription. It lies just before the gene and holds the −35 and −10 sequences.
  2. −35 sequence A short stretch about 35 base pairs before the start site. With the −10 sequence it marks where RNA polymerase binds.
  3. −10 sequence (Pribnow box) A short stretch about 10 base pairs before the start site. Its usual letters are TATAAT, and it is also called the Pribnow box.
  4. Transcription start site The first base that is copied into RNA. Positions before it are counted backward, which gives −35 and −10 their names.
  5. Terminator The sequence at the end of the gene where transcription stops. The RNA copied from it can fold into a hairpin, which frees the mRNA.
  6. mRNA The RNA copy of the gene, from start site to terminator. In bacteria ribosomes begin to translate it while it is still being made.

The mRNA 6

  1. Ribosome-binding site (Shine-Dalgarno sequence) The ribosome attaches to the mRNA here. In bacteria it is the Shine-Dalgarno sequence, usually AGGAGG, a few bases before the start codon.
  2. Start codon Usually the three bases AUG, where translation begins. The coding sequence runs from here to the stop codon.
  3. Coding sequence The part of the mRNA that is translated into protein. In bacteria it is almost never interrupted by introns.
  4. Stop codon Three bases that end translation: UAA, UAG or UGA. No amino acid is added for it.
  5. 5′ untranslated region The stretch of mRNA before the start codon. It is not translated, it holds the ribosome-binding site, and in bacteria it is short.
  6. 3′ untranslated region The stretch of mRNA after the stop codon. It is not translated into protein.

How this list was compiled: Every name checked on 2026-10-03 against the US National Human Genome Research Institute glossary (Promoter, Stop Codon, Open Reading Frame, Messenger RNA); Nature Education, Scitable: DNA Transcription; Translation: DNA to mRNA to Protein; RNA Splicing: Introns, Exons and Spliceosome; Wikipedia, text only: Promoter (genetics), Pribnow box, Shine-Dalgarno sequence, Terminator (genetics), Bacterial transcription, Gene structure, Start codon; Kimball's Biology Pages: Gene Translation; Gene Expression: Transcription; and, for the start codon, Jeremy W. Dale, Molecular Genetics of Bacteria (1998), read through full-text search. Licence: own work

The drawing: Drawn for this site on 2026-10-03 by script from a table of positions; nothing traced. Licence: own work

How it works

A bacterial gene is a stretch of DNA with a promoter in front of it and a terminator at its end. The first chart shows the gene on the DNA; the second shows its mRNA, the message a ribosome reads.

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The gene: read it from left to right

RNA polymerase binds at the promoter, which holds the −35 and −10 sequences. The bent arrow marks the transcription start site. Transcription runs along the gene to the terminator, and the wavy line under the gene is the mRNA it makes.

The message: where translation starts and stops

A ribosome attaches at the ribosome-binding site and begins at the start codon. It reads the coding sequence as far as the stop codon. The stretches before the start codon and after the stop codon are the untranslated regions.

  • The −35 box is the one farther from the bent arrow.
  • 5′ and 3′ mark the two ends of the mRNA; a ribosome reads from 5′ to 3′.

Questions and answers

What are the components of a bacterial gene?

A promoter, where RNA polymerase binds; the transcribed region, which begins at the transcription start site and holds the coding sequence; and a terminator, where transcription stops. The mRNA made from it has a ribosome-binding site and an untranslated region at each end.

How do I label the diagram to examine bacterial gene structure?

Work from left to right. On the DNA: the −35 sequence, the −10 sequence, the transcription start site, the gene, the terminator. On the mRNA: the ribosome-binding site and the start codon come before the coding sequence, the stop codon after it.

What are the −35 and −10 sequences?

Two short stretches of DNA in a bacterial promoter, about 35 and 10 base pairs before the transcription start site. The sigma subunit of RNA polymerase finds the promoter. The −10 sequence, usually close to TATAAT, is also called the Pribnow box.

What is the Shine-Dalgarno sequence?

The ribosome-binding site of a bacterial mRNA: a short sequence, usually AGGAGG, a few bases before the start codon. It lies in the 5′ untranslated region, and a ribosome attaches there to begin translation at AUG.

Do bacterial genes have introns?

Almost never. Most bacterial RNA is not spliced, so the mRNA matches the gene base for base. A bacterium also begins to translate an mRNA while it is still being transcribed.

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