Genetic regulation

Purpose:

Instead of expressing all genes at all times, cells ‘choose’ to only transcribe and translate the genes they need at this particular time.

This process of choosing how much and when to express genes is called gene regulation.

Genetic regulation allows cells to conserve energy by avoiding producing unnecessary proteins and adapt to changing environments. In multicellular organisms, gene regulation also enables cellular differentiation, allowing different cell types to express unique sets of genes despite having the same genetic material.

Gene Structure

Introductory True / False Question

Answer

Parts of a gene:

If you were to draw a picture of a gene in an exam, what features would you need to draw?]

student respones

*student meant to put introns and exons

Answer: what features to include?

• Promoter (This is drawn ‘upstream’ of a gene (‘upstream’ means it is on the 5' end of a gene, i.e. closer to the START codon than to the STOP codon). It is standard to draw the promoter to the left of the gene, but as long as the promoter is closer to the START codon, then you’ve drawn it correctly.
• START & STOP codons
• Exons & Introns Note: this aspect is not always necessary, as some genes don’t have introns, but if you know a gene has introns you should draw them! If you haven’t been told whether this gene has introns you might be able to get away with not drawing introns and exons …

Function of each aspect of gene structure:

The promoter?

Prior student responses

Answer: what is the function of the promoter?

Site where RNA polymerase binds to start transcription

Introns and exons?

Prior student responses

Reveal exon and intron roles:

Introns are regions of the gene which are spliced out of the premRNA molecule (and so do not code for amino acids, so they are sometimes also called non-coding regions). Exons code for amino acids, so they get to 'exit' the nucleus.

START / STOP codon

Reveal START / STOP codon role

Instruct ribosomes as to when to start / stop translation

Gene Structure Drawing

• When drawing a gene in a VCAA exam make sure to label the promoter, the START / STOP triplet and introns and exons. Labelling is key!

Types of Genes

Regulatory genes: encode specific proteins products which regulate the level of activity of other genes

Structural genes: encode specific proteins products (that don’t do gene regulation tasks)

Additional resources