DNA is the blueprint of life. Every living thing from bacteria to plants, animals and humans have DNA in their body cells; it is responsible for the function of every cell in the body and the body itself at large. The growth, development, metabolism, reproduction, inheritance, vulnerability to diseases etc regarding to the living things is all encoded within the sequences of its DNA.
Genome editing is a type of genetic engineering in which DNA is inserted, deleted, modified or replaced in the genome of a living organism.
With genome editing, scientists can design (i) better and stronger breeds of animals (ii) plants with high resistance to drought and diseases (iii) correct genetic mutations in plants, animals and humans_(iv)_ prevent and cure diseases including cancer in humans.
CRISPR is the latest technology used in gene editing. CRISPR allows scientists to make modifications to DNA, but unlike other techniques, it is simpler, faster, cheaper and more accurate.
Body cells including immune cells can be removed from the body, genetically modified in the lab and then reinsert into the body.
“The technology is unbelievable,” says Kamel Khalili of Temple University in Philadelphia, who thinks it could clear viruses like HIV from the body.
...“CRISPR is evolving incredibly fast,” says Waseem Qasim of University College London, whose team recently used an older form of gene editing to save the life of a baby with leukaemia. “We can’t keep up.”
CRISPR [pronounced "crisper"] is a short for Clustered Regularly Interspaced Short Palindromic Repeats. It is the hallmark of a bacterial defense system.
One of the techniques discovered is known as CRISPR-Cas9, which is short for clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9. CRISPR is the hallmark of a bacterial defense system that forms the basis for CRISPR-Cas9 genome editing technology.
CRISPR-Cas9 was adapted from a naturally occurring genome editing system in bacteria. The bacteria capture snippets of DNA from invading viruses and use them to create DNA segments known as CRISPR arrays. The CRISPR arrays allow the bacteria to "remember" the viruses (or closely related ones). If the viruses attack again, the bacteria produce RNA segments from the CRISPR arrays to target the viruses' DNA. The bacteria then use Cas9 to cut the DNA apart which disables the virus.
Although enzyme Cas9 is often used, other similar enzymes including CPF1, Cas13 can be programmed to target specific sequences of genetic code and to edit DNA in the laboratory.
Gene editing as a therapeutic technique is of two classes:
(i) Germline therapy
(ii) Somatic therapy.
Germline therapy can modify genes in all cells including reproductive cells (sperm and eggs). These modifications can be inherited i.e. passed down from generation to generation. It could potentially prevent inheritance of diseases like sickle cell anaemia and down syndrome.
Somatic therapy on the other hand, target non-reproductive cells only. Changes made in these cells affect only the person who receives the gene therapy and do not pass on to future generations.
...CRISPR is seen as the future of medicine, although there are still significant technical barriers it is facing and need to understand.
- Ethics and safety of potential treatment.
- How to determine and deliver the genome editing therapy to the concerned cells in the body in an effective manner.
- How different changes in these genes can affect a person's life in short and long term as many genes have more than one function. And in some cases editing a gene to cure one disease could create another.
- How genetic changes and environmental influences combine to result in disease.
- How genes (both modified and normal) interact with each other in the same body system.
References:
- https://ghr.nlm.nih.gov/primer/genomicresearch/genomeediting
- https://www.broadinstitute.org/what-broad/areas-focus/project-spotlight/questions-and-answers-about-crispr
- https://www.npr.org/sections/health-shots/2019/04/16/712402435/first-u-s-patients-treated-with-crispr-as-gene-editing-human-trials-get-underway
- https://www.newscientist.com/article/mg22830500-400-editing-life-a-guide-to-the-genetic-revolution-on-our-doorstep/
- https://www.genome.gov/27569224/how-is-genome-editing-used/
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