Gene Expression: notes and practice questions
- This topic explores the mechanisms by which genetic information is expressed and regulated in cells.
- Gene expression involves transcription (DNA to RNA), translation (RNA to protein), and the function of the protein product.
- Regulation occurs at the transcriptional level through proteins binding to specific DNA sequences like promoters and enhancers.
- mRNA degradation is a mechanism for regulating translation.
- Epigenesis describes phenotypic changes without altering DNA base sequences, often due to epigenetic tags such as DNA methylation and histone modification.
- Epigenetic changes can be inherited across cell divisions or generations.
- The genome, transcriptome, and proteome differ between cells because not all genes are expressed simultaneously.
- Environmental factors, hormones, and biochemicals can influence gene expression patterns.
How it is examined
HL only. The most common item is distinguish between genome, transcriptome and proteome, where all three definitions are needed. Epigenetics questions reward the phrase "without a change in the base sequence", and an answer that describes a mutation instead scores nothing. The liger and tigon example is worth having, because the mark scheme often credits a named example separately.
There is no SL content in D2.2. The whole subtopic is HL.
Do not set this topic for SL students.
Guiding questions
- How is gene expression changed in a cell?
- How can patterns of gene expression be conserved through inheritance?
Linking questions
- What mechanisms are there for inhibition in biological systems?
- In what ways does the environment stimulate diversification?
Practice questions
1 question · 1 hardQuestion 1
HardPaper 2 · calculator15 marksGene expression and protein function are highly regulated processes that allow cells to respond to their environment and maintain homeostasis.
(a) Outline how gene expression can be regulated at the stages of transcription and translation.
(b) Explain the mechanism by which a steroid hormone, such as oestradiol, initiates gene expression.
(c) Explain how the activity of cellular proteins, such as enzymes and receptors, can be controlled or inhibited after they have been synthesized.
Think about what can bind to DNA to stop transcription, how epigenetic tags affect DNA coiling, and what happens to mRNA to prevent it from being translated.
Consider the chemical nature of steroid hormones. How do they enter the cell, what do they bind to inside, and how does this complex interact with DNA?
Discuss how ligands activate proteins, and describe the three main types of enzyme inhibition (competitive, non-competitive/feedback, and mechanism-based), providing a named example for each.
No question on this page matches those filters. Try another difficulty or paper.
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Where marks are lost
- Command terms are consistently under-read. Students answer describe when the question said explain, so they give an account with no reasons and cap at half marks. The reverse also happens on outline, where a student writes an essay for a 2-mark summary and runs out of time.
