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VICBiologyQuick questions
Unit 3: How do cells maintain life?
Quick questions on Gene structure and regulation (trp operon): VCE Biology Unit 3
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are regulator genes?Show answer
A regulator gene codes for a protein (often a transcription factor) that controls the expression of one or more target genes. Regulator gene products may be:
What is the trp operon (worked prokaryotic example)?Show answer
An operon is a cluster of genes under a single promoter, transcribed as one mRNA. They are common in prokaryotes such as Escherichia coli.
What is promoter?Show answer
A non-coding region upstream of the start of transcription. It contains binding sites for transcription factors and RNA polymerase, often including a TATA box. The promoter is not transcribed; it positions the polymerase.
What are exons?Show answer
The coding regions, retained in the mature mRNA and translated. The order of exons (and their alternative combinations through splicing) determines the protein sequence.
What are introns?Show answer
Non-coding regions inside the gene, transcribed into pre-mRNA but removed by the spliceosome during RNA processing.
What is terminator?Show answer
A sequence at the 3' end that signals RNA polymerase to release the transcript.
What are regulatory elements?Show answer
Enhancers and silencers (further from the gene) can be bound by transcription factors that increase or decrease the rate of transcription.
What is q1?Show answer
State three structural components of a eukaryotic gene and their function. [3 marks]
What is q2?Show answer
A geneticist deletes the operator sequence from the trp operon. Predict the effect on transcription when tryptophan is plentiful, and explain. [3 marks]
What is q3?Show answer
Refer to the trp operon in E. coli. (a) Distinguish a repressible from an inducible operon.