Intron vs Operon

[Avicenna]

Are introns the same as repressed operons, or are they do different things?

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[EverStriving]

They're two completely different mechanisms.

An operon is a chunk of DNA that is under the transcriptional control of a single promoter. There may be multiple genes in a single operon.

In eukaryotes, introns are regions of transcribed DNA that don't code for proteins because they are spliced out of the RNA before it becomes mRNA. Therefore introns do not make it to the translation stage.

 

[bearintraining]

No. there are several differences.

Introns are sequences in the DNA that is spliced out of the mRNA transcript in eukaryotes only. They do not code for protein. They may contain gene regulatory information (unlikely to appear on the MCAT ever).

Operons are a bacterial segment of DNA that contains a Promoter (where transcription starts), an Operator (regulatory sequence), and several genes that are transcribe on a single mRNA, and thus a polycistronic (cistron = gene) transcript.

 

[EverStriving]

Operons aren't strictly bacterial. There are eukaryotic operons as well, although they are rare.

 

[Avicenna]

AGGH i hate this dna section. welp thanks guys back to the books

 

[bearintraining]

Operons aren't strictly bacterial. There are eukaryotic operons as well, although they are rare.

The "operons" in eukaryotes are quite different. It's not really the same at all.

 

[EverStriving]

The "operons" in eukaryotes are quite different. It's not really the same at all.

The operons in eukaryotes (eg c. elegans) are groups of genes under the control of a single promoter, and are transcribed as a single polycistronic RNA. Not sure what would make them different enough to not consider them true operons.

 

[Cotterpin]

Can eukaryotic operons be inducible or repressible? They must be, right? So what is the difference?

 

[bearintraining]

The operons in eukaryotes (eg c. elegans) are groups of genes under the control of a single promoter, and are transcribed as a single polycistronic RNA. Not sure what would make them different enough to not consider them true operons.

If you read the review on eukaryotic operons you'll notice that they don't behave exactly the same way. They are often spliced into monocistronic mRNAs even if derived from polycistronic primary mRNAs. Some of the other events are also different, and the one definition regarding alternative splicing of exons is questionable whether that truly represents an operon.

Can eukaryotic operons be inducible or repressible? They must be, right? So what is the difference?

Yes, as a general rule all genes can be induced or repressed.
The devil is in the details. Either way, I wouldn't expect there to be a eukaryotic operon on the MCAT.