Liposomes and Lipoprofection in Gene Therapy
About 10% of gene therapy trials have used liposomes . These are hollow microscopic spheres of phospholipid, and can be filled with DNA or other molecules during assembly. The liposomes will merge with the membranes surrounding most animal cells and the contents of the liposome end up inside the cell, a process known as lipofection […]
Retrovirus Gene Therapy for SCID
Severe combined immunodeficiency (SCID) occurs when both the B cells and T cells of the immune system are defective and results in an almost totally defective immune response. Children with SCID have to be shielded from all contact with other people and are kept inside special sterile plastic bubble chambers. Without immune protection any disease, […]
Retrovirus Gene Therapy
Retroviruses infect many types of cells in mammals. They need dividing cells for successful infection, and will not infect many tissues where host cell growth and division have come to a standstill. Moreover, the genetic material of retroviruses passes through both DNA and RNA stages. This means that introns must be removed from any therapeutic […]
Cystic Fibrosis
About one in 2000 white children suffer from cystic fibrosis . This condition is due to homozygous recessive mutations. In other words two defective copies of the gene, one from each parent, must be inherited for the child to suffer from the disease. Humans with a single defective allele are carriers but do not show […]
Adenovirus Vectors in Gene Therapy
Adenoviruses are relatively simple, double-stranded DNA viruses that infect humans and other vertebrates. The virus particle consists of a simple icosahedral shell, or capsid, containing a single linear dsDNA molecule of approximately 36,000 base pairs. A terminal protein protects each end of the DNA. The capsid is made of 240 hexons , each of which is […]
Aggressive Gene Therapy
The original idea behind gene therapy was curing hereditary defects by replacing defective genes. However, there is no inherent reason why gene therapy must only be “defensive” and suppress defects. We can go on the offensive and provide genes whose products may cure a disease even though the genes we use were not responsible for […]
Gene Patching by Oligonucleotide Crossover
During replacement gene therapy, we normally think of replacing the whole defective gene with a complete functional copy. However, some genetic defects consist of just a single base change, or perhaps a cluster of closely linked base alterations. In this case, the defective gene could be “patched” rather than replaced. This may be done by […]
Gene Therapy
Genetic engineering means that we alter an organism permanently so that the changes will be stably inherited. For multicellular organisms this implies deliberate alteration of the DNA in the germline cells. In contrast, gene therapy (occasionally called genetic surgery ) is less permanent. The patient is cured, more or less, by altering the genes in […]
Polymerase Chain Reaction
The polymerase chain reaction (PCR) amplifies small samples of DNA into large amounts, much as a photocopier makes many copies of one sheet of paper. The DNA is amplified using the principles of replication, that is, the DNA is replicated over and over by DNA polymerase until a large amount is manufactured. Kary Mullis invented this […]
Getting Cloned Genes into Bacteria by Transformation.
Once the gene of interest is cloned into a vector, the construct can be put back into a bacterial cell through a process called transformation. Here the “naked” DNA that was constructed in the laboratory is mixed with competent E. coli cells. Calcium ions To make the cells competent, that is, able to take up […]