Gene therapy, gene editing, microarrays and bioinformatics

Last time

Before we start: last time, in Threats, conservation, invasive species and assisted reproduction, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Fixing the fault itself

Most medicines treat symptoms. Gene therapy and gene editing try to treat the cause, by changing the D N A. Microarrays and bioinformatics are the reading tools that tell us which genes to target, and what the cell's genes are doing. This final lesson in genetic technology joins them together.

Gene therapy

Gene therapy is the introduction of a functional allele into the cells of a person with a genetic disease, to make up for a faulty allele. The gene is carried by a vector, often a modified virus, with its disease causing genes removed. The vector enters the target cells and the working gene is expressed. Somatic gene therapy treats body cells, and the change is not inherited. Germline therapy would change gametes or embryos, and is banned in most countries.

Treating SCID

Severe combined immunodeficiency, S C I D, can be caused by a mutation in the A D A gene. Lymphocytes lack the enzyme adenosine deaminase and die, so the child has almost no immune system. Treatment: remove bone marrow stem cells from the patient, insert a working A D A gene using a viral vector, and return the corrected cells to the body. The treated stem cells divide and make healthy lymphocytes. The effect can last, but there is a risk the vector inserts in the wrong place and causes cancer.

A past-paper example

May June 2026, Paper 41, question 10. Genetic engineering can be applied to medicine. Outline how S C I D can be treated by gene therapy. Six marks. Take cells from the patient, such as stem cells. Use a vector to insert a functional A D A allele. Return the modified cells so they divide and make functional lymphocytes. Mention the risks and the benefits.