Gene expression: regulate products, not just genes
| English | 中文 | Pinyin |
|---|---|---|
| transcription factor/trænˈskrɪpʃn ˈfæktə/ | 转录因子 | zhuǎn lù yīn zi |
| epigenetic modification/ˌepɪdʒɪˈnetɪk ˌmɒdɪfɪˈkeɪʃn/ | 表观遗传修饰 | biǎo guān yí chuán xiū shì |
What would explain this observation?
- Two cells with the same genome make different proteins. Regulation changes which information is used and when.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Gene expression can be regulated at transcription and later stages. A transcription factor 转录因子 can affect transcription through interactions with DNA and other proteins. Epigenetic modifications 表观遗传修饰 can influence expression without changing the underlying DNA sequence.
- transcription factor: A protein that influences transcription; epigenetic modification: A change affecting expression without changing the DNA sequence.
What is justified by higher measured mRNA abundance?
Distinguish a measured mRNA change from a protein or functional change. Translation, degradation and protein modification can all intervene. Regulation is specific to a cell context and environmental conditions.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Distinguish a measured mRNA change from a protein or functional change. Translation, degradation and protein modification can all intervene. Regulation is specific to a cell context and environmental conditions.
- Compare treated and control expression data after checking normalization and replicates. Use evidence from a supplied perturbation to discuss causal models, rather than equating every association with a direct mechanism.
Which two habits make the investigation or model in this case more defensible?
Compare treated and control expression data after checking normalization and replicates. Use evidence from a supplied perturbation to discuss causal models, rather than equating every association with a direct mechanism.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: normalized transcript abundance is 12 in treatment and 3 in control. Fold change = 12/3 = 4. Equal normalized abundance does not require equal absolute cell counts in the two raw samples.
Transcript abundance is 15 in treatment and 5 in control. Find fold change. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Transcript abundance is 15 in treatment and 5 in control. Find fold change.
The result is 3 . Known: normalized transcript abundance is 12 in treatment and 3 in control. Fold change = 12/3 = 4. Equal normalized abundance does not require equal absolute cell counts in the two raw samples.
Check the conclusion and its limits
- An epigenetic change is not automatically a DNA-sequence mutation. More mRNA does not guarantee proportionally more active protein.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Every change in gene expression is a mutation. This claim is false: An epigenetic change is not automatically a DNA-sequence mutation. More mRNA does not guarantee proportionally more active protein.
Gene expression: regulate products, not just genes: Distinguish a measured mRNA change from a protein or functional change. Translation, degradation and protein modification can all intervene. Regulation is specific to a cell context and environmental conditions.
Every change in gene expression is a mutation.
An epigenetic change is not automatically a DNA-sequence mutation. More mRNA does not guarantee proportionally more active protein.
A protein that influences transcription: write the technical term.
transcription factor means A protein that influences transcription.