Gene expression: regulate products, not just genes
הוצג| English | משמעות |
|---|---|
| transcription factor/trænˈskrɪpʃn ˈfæktə/ | גורם תעתיק |
| epigenetic modification/ˌepɪdʒɪˈnetɪk ˌmɒdɪfɪˈkeɪʃn/ | שינוי אפיתרגני |
What would explain this observation?
- Two cells with the same genome make different proteins. Regulation changes which information is used and when.
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?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Higher mRNA abundance shows more of that transcript under the measured conditions - nothing more. Protein level also depends on translation and degradation, and an expression change says nothing about the DNA sequence.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
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.
In the lab: 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?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- 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.
Your turn: Transcript abundance is 15 in treatment and 5 in control. Find fold change.
Transcript abundance is 15 in treatment and 5 in control. Find fold change.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 3 . Known: abundance 15 in treatment, 5 in control. Use fold change = treatment / control. Fold change = 15/5 = 3. Normalized abundance can be compared without equal raw cell counts.
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.
Not true: Every change in gene expression is a mutation. Expression changes are regulatory - the same DNA is read more or less often. A mutation is a change in the DNA sequence itself; most changes in expression involve no mutation at all.
- Gene expression can be regulated at transcription and later stages.
- Distinguish a measured mRNA change from a protein or functional change.
- Watch for: an epigenetic change is not automatically a DNA-sequence mutation.
Write from a transcript fold change of 5
- Normalized transcript abundance is 20 in the treatment and 4 in the control.
- Find the fold change. An mRNA change is not automatically a protein change.
Every change in gene expression is a mutation.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Expression changes are regulatory - the same DNA is read more or less often. A mutation is a change in the DNA sequence itself; most changes in expression involve no mutation at all.
A protein that influences transcription: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
transcription factor means A protein that influences transcription.
Normalized transcript abundance is 20 in the treatment and 4 in the control. What is the fold change, and why might the protein change be different?
20 divided by 4 is 5. The transcript measurement stops before those later steps.
What is the transcript fold change?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
20 divided by 4 is 5.