Genetic Therapies Types

Genetic therapies may use gene transfer or genome editing approaches to change the DNA in a patient’s cells to treat a condition.

Gene transfer

Gene transfer introduces an additional gene into specific cells. This gene may stay as an extra piece of DNA in the cell or be inserted into the cell’s own chromosomes to become part of the cell’s own DNA.

A molecular package called a vector carries the gene to the cell nucleus, the central part of the cell where DNA is packaged in chromosomes. Vectors are created in the laboratory, often from viruses that have been modified to remove viral genes that cause disease and to carry a treatment gene.

Once the gene is inside the nucleus, the cell will start to make the critical protein needed for the cell to work properly. The new proteins make up for missing or faulty proteins and are meant to improve health for people who receive genetic therapies.

Illustration of gene transfer — **Gene transfer.** One image of a cell containing a gene with a mutation that makes a faulty protein and one image of the same cell after successful gene transfer. Medical Illustration Copyright © 2022 Nucleus Medical Media, All rights reserved.

Genome editing

Genome editing introduces components that work together into cells. One component is a protein that cuts DNA, similar to a pair of molecular scissors. Another component is a guide molecule that can stick to DNA at specific sites. When the guide molecule sticks to an area of faulty DNA, the scissors protein attaches to the guide molecule and cuts out the faulty DNA.

After the target DNA is cut, several things can happen. The cell may leave behind a gap, return the DNA to its original state, or fill in this gap with the corrected DNA. The cell can fill in the corrected DNA if it has a template DNA to direct the cell to rebuild a healthier version of the DNA that was removed. Therefore, sometimes a small piece of template DNA is introduced as a third component. This DNA is a corrected version of the faulty DNA, and it is used to rebuild the DNA correctly after it is cut open.

Illustration of genome editing — **Genome editing.** One image of a cell containing a gene with a mutation that makes a faulty protein and one image of the same cell after successful gene editing. In this case, genome editing repairs the gene itself, rather than adding an extra gene. Medical Illustration Copyright © 2022 Nucleus Medical Media, All rights reserved.