Gene regulation

Question 1

what does gene regulation do?

Answer 1

Gene regulation is important for energy conservation if the protein isn’t needed the cells won’t express the gene

Question 2

Structural genes

Answer 2

Express structural (e.g keratin) and/or functional proteins (e.g hormones, enzymes

Question 3

Regulatory genes

Answer 3

Express proteins (also known as transcription fcators) that control the activity of structural genes - switching them on and off (activator/repressors)

Question 4

gene structure

Answer 4

Regulatory gene: controls the expression of a structural gene
Non-coding region: Binding site for transcription enzymes
Operator: the area between promotor and structural gene where repressor binds to inhibit the expression (only in prokaryotes)
Structural gene: codes for a functional protein

Question 5

Trp Operon

Answer 5

Bacteria have genes grouped together, called an operon that is transcribed together and can be switched on/off as required.
The Trp operon is a set of 5 structural genes (trpE, trpD, trpC, trpB, trpA) in bacteria involved in the production of amino acid tryptophan

Question 6

high levels of trp in cell (On/off repressor)

Answer 6

activates the repressor -> conformational change -> bind to repressor

THE RESULT: stops transcription (turns off the gene)

Question 7

low levels of trp in cell (On/off repressor)

Answer 7

the repressor is inactive -> unable to bind to the operator
RESULT: transcription occurs (turns on the gene)

Question 8

Trp operon - Attenuation (another method of regulation)

Answer 8

between the operator and the first gene of the o[eron there are sections called leader and attenuator - these sections are transcribed with operon genes

The LEADER: codes for a short polypeptide - and includes two trp codons.

the ATTENUATOR does not code for a polypeptide.

when transcribed into mRNA, these sections have self-complementary sequences that can form hairpin structures

Question 9

high levels of trp in cell (Attenuation )

Answer 9

leader gene is transcribing without stalling -> terminator hairpin -> pulls RNA polymerase off the DNA

RESULT: stops transcription (turns the gene off)

Question 10

low levels of trp in cell (Attenuation )

Answer 10

leader gene is stalled during transcription Attenuation of trp -> forms an anti-terminator hairpin

RESULT: transcription occurs (turns on the gene)