Quick questions on Recombinant DNA, CRISPR, whole genome sequencing and gene therapy: HSC Biology Module 6

The classical biotechnology toolkit, established in the 1970s. It combines DNA from different sources into a single molecule.

Discovered as a bacterial immune system; reprogrammed for genome editing by Doudna and Charpentier (Nobel Prize 2020).

What it is. Reading every base of an organism's genome, usually using next-generation sequencing technologies that read millions of short fragments in parallel and assemble them computationally.

What it is. Inserting, correcting or silencing a gene in a patient's cells to treat a genetic disease.

Reproductive cloning. Somatic cell nuclear transfer (SCNT): the nucleus of a somatic cell is inserted into an enucleated egg, producing an embryo genetically identical to the donor.

Recombinant human insulin: the human insulin gene is cut with restriction enzymes, ligated into a plasmid, transformed into E. coli, and grown in industrial fermenters; the bacteria secrete human insulin, which is purified for clinical use.

Knock-out cell lines for research, agricultural traits (mildew-resistant wheat, polled cattle, mushroom browning), gene therapy (Casgevy, approved 2023 for sickle cell disease and beta-thalassaemia).

Reading every base of an organism's genome, usually using next-generation sequencing technologies that read millions of short fragments in parallel and assemble them computationally.

Somatic cell nuclear transfer (SCNT): the nucleus of a somatic cell is inserted into an enucleated egg, producing an embryo genetically identical to the donor.

A working beta-globin gene is delivered to haematopoietic stem cells using a lentiviral vector. The cells are returned to the patient and produce functional haemoglobin. This is the approach used by Zynteglo.

CRISPR-Cas9 is used to disrupt the BCL11A gene in the patient's stem cells, reactivating fetal haemoglobin (HbF), which is not affected by the sickle mutation. The edited cells are returned to the patient. This is the approach used by Casgevy (approved 2023).

Recombinant DNA inserts new sequence into a vector; CRISPR edits existing sequence in place.

Somatic = body cells, not heritable; germline = gametes or embryos, heritable and largely banned.

It has fewer than older editing tools, but off-target cuts at similar sequences are a real risk that researchers actively screen for.

WGS is a diagnostic technology; it tells you what is wrong, but does not directly treat anything.