Manipulating Gene Expression – Key Vocabulary

Vocabulary flashcards covering major terms, enzymes, repair pathways, technologies, clinical applications and ethical issues related to RNAi and CRISPR-based gene manipulation presented in the lecture.

Central Dogma of Biology

Concept describing the flow of genetic information from DNA → RNA → Protein by transcription and translation.

RNA Silencing (RNAi)

Natural cellular process in which double-stranded RNA triggers degradation of complementary mRNA, preventing translation.

RNA Interference (RNAi)

Laboratory and therapeutic exploitation of RNA silencing to reduce or abolish expression of a specific gene.

siRNA (Small Interfering RNA)

~21-nt double-stranded RNA molecules, often synthetic, that guide RISC to complementary mRNA for degradation.

miRNA (MicroRNA)

Endogenously encoded small RNAs processed from hairpin precursors that regulate gene expression post-transcriptionally.

Double-Stranded RNA (dsRNA)

RNA consisting of two complementary strands; potent trigger of RNAi mechanisms.

Dicer

RNase III enzyme that cleaves long dsRNA or pre-miRNA into ~21-nt siRNA/miRNA fragments.

RISC (RNA-Induced Silencing Complex)

Protein–RNA complex (with Argonaute) that uses single-stranded siRNA or miRNA to identify and cleave target mRNA.

Argonaute 2 (AGO2)

Catalytic component of RISC responsible for endonucleolytic cleavage of target mRNA.

Gene Knockdown

Reduction (but not complete elimination) of gene expression, often via RNAi.

Gene Knockout

Complete loss of gene function, commonly achieved by CRISPR-induced frameshift mutations or deletions.

CRISPR

Clustered Regularly Interspaced Short Palindromic Repeats—bacterial DNA loci forming part of an adaptive immune system.

Cas (CRISPR-Associated) Protein

Nuclease enzyme guided by CRISPR RNA to cleave foreign or targeted DNA sequences.

Cas9

RNA-guided endonuclease widely used for genome editing to create double-strand DNA breaks at specific sites.

Endonuclease

Enzyme that cuts phosphodiester bonds within a nucleic acid strand (as opposed to exonucleases that trim ends).

Guide RNA (gRNA)

Synthetic fusion of crRNA and tracrRNA that programs Cas9 to a complementary genomic target sequence.

PAM (Protospacer Adjacent Motif)

Short DNA sequence immediately downstream of the target site essential for Cas9 binding and cleavage (e.g., NGG for SpCas9).

Non-Homologous End Joining (NHEJ)

Fast, error-prone DNA repair pathway that ligates broken DNA ends, often introducing insertions/deletions (indels).

Homology-Directed Repair (HDR)

High-fidelity DNA repair pathway using a homologous template to precisely mend double-strand breaks, enabling specific edits.

Base Editor

CRISPR-derived tool that chemically converts one DNA base to another without creating double-strand breaks.

Prime Editor

CRISPR-based system using a reverse-transcriptase–fused Cas9 nickase and pegRNA to install precise edits without DSBs.

Germline Editing

Genomic alteration of gametes or embryos that can be inherited by future generations; raises major ethical concerns.

Somatic Editing

Genome modification of non-reproductive cells; changes are not heritable.

BCL11A

Transcription factor that represses fetal haemoglobin; CRISPR deletion in bone-marrow cells can alleviate sickle-cell disease.

Fetal Haemoglobin (HbF)

Haemoglobin isoform expressed before birth; re-expression in adults can mitigate sickle-cell and β-thalassaemia symptoms.

Patisiran

First FDA-approved RNAi drug (2018) that delivers siRNA to silence transthyretin in hereditary amyloidosis.

Genome Editing

Intentional alteration of DNA sequence at specific loci using engineered nucleases such as CRISPR-Cas systems.

Gene Therapy

Treatment of disease by modifying or manipulating gene expression within a patient’s cells.

Off-Target Effects

Unintended genomic modifications or gene silencing events caused by imperfect specificity of editing or RNAi tools.

Andrew Fire & Craig Mello

Scientists awarded the 2006 Nobel Prize for discovering RNA interference.

Emmanuelle Charpentier & Jennifer Doudna

Recipients of the 2020 Nobel Prize in Chemistry for developing CRISPR-Cas9 genome-editing technology.

Jiankui He

Chinese researcher who claimed (2018) to create CRISPR-edited babies, later jailed for unethical medical practices.

Exa-cel (Casgevy)

CRISPR/Cas9 therapy submitted for regulatory approval (2023) to treat sickle-cell disease and β-thalassaemia.

Ethical Implications of Gene Editing

Societal, legal and moral issues surrounding safety, consent, equity, and heritability of genome modifications.

Homologous Recombination

Exchange of genetic information between similar DNA sequences, foundational for HDR-mediated editing.