Learning Objective: At the end of this lesson, the learner will be able to describe the strategies used to modify gene expression in model organisms and understand RNA-based techniques for silencing or regulating gene expression.
Transgenic Strategies in Mice
| Strategy | Description | Outcome |
|---|---|---|
| Random insertion | Gene is inserted randomly into the mouse genome | Constitutive expression (always on) |
| Targeted insertion/deletion (homologous recombination) | Gene is inserted or removed at a specific locus | Conditional or precise expression/knock-out or knock-in |
Key Terms:
- Knock-out: Removing a gene to study loss-of-function effects
- Knock-in: Inserting a gene to study gain-of-function or express a humanized gene
Clinical / Research Applications:
- Study of genetic diseases
- Modeling human disorders in mice
- Functional analysis of genes
RNA Interference (RNAi)
RNA interference is a post-transcriptional gene silencing mechanism using small non-coding RNA molecules that target mRNA.
| Type | Source / Description | Mechanism | Specificity | Notes / Clinical Relevance |
|---|---|---|---|---|
| microRNA (miRNA) | Endogenously produced hairpin RNAs | Partial binding to mRNA → blocks translation ± mRNA degradation | Broad targeting of related mRNAs | Abnormal expression can silence tumor suppressors → malignancy |
| small interfering RNA (siRNA) | Usually exogenous dsRNA (virus or synthetic) | Complete pairing → mRNA cleavage before translation | Highly specific to target mRNA | Used experimentally for gene knockdown and therapeutic applications |
High-Yield Points
- miRNAs regulate multiple mRNAs due to partial complementarity.
- siRNAs are highly specific and often used experimentally to silence individual genes.
- Transgenic mice allow functional studies of genes in vivo through knock-out or knock-in strategies.
