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Gene Editing using Engineered Nucleases-Jenny Sheng
Transcript of Gene Editing using Engineered Nucleases-Jenny Sheng
biotechnology... Genome editing with Engineered Nucleases Your typical DNA looks like this: There are two parts to
engineered nucleases: Binding proteins: Nucleases: Nucleases are the molecular
scissors that cut the DNA Binding proteins bind to DNA bases before any cutting can occur After binding proteins have bound to DNA, nucleases will cut DNA at the recognized sites Two things can happen once the DNA is cut: Deletion: Substitution: The strand that was cut can be deleted entirely. The strand that was
cut can be replaced
with another. The process... Zinc Finger Nucleases Transcription Activator-Like Effector Nucleases (TALENs) There are two types of engineered nucleases... Now that we understand the process of
using engineered nucleases let us examine
the actual engineered nuclease in detail... Zinc Finger Nucleases and TALENs zinc fingers proteins are abundant in humans and are responsible for turning genes on and off. In order to use them in genetic editing, they are encoded into plasmids. Each zinc finger plasmid is designed to recognize a sequence base pairs. One plasmid will interact and bond with a sequence of three bases Advantage: The advantage of using ZFN is that they can be engineered to recognize specific sites. COmpared to a restriction enzyme that may cut in multiple places, the more specific a ZFN is, the more targeted the cutting becomes. Disadvantage: Some zinc-fingers do not interact well next to each other. If zinc finger A binds to the first three base pairs (CGC) and Zinc finger B binds to the next group of base pairs (ATA), one may think that by putting them together, they will recognize sequence CGC ATA. That is not the case. Zinc finger A and B may not interact well next to each other. In fact, a lot of research has gone into making a database of labeling all the zinc fingers that do and do not interact well with each other. The other type of engineered nuclease is called TALENs. TAL proteins come from bacteria that infect plants. TALENs are very similar to Zinc-finger Nucleases except one TALENs plasmid interacts with only one base. Advantage: TALENs' unique way of binding one plasmid to one base is an advantage in that the individual plasmids do not seem to interfere with each other. This solves the problem that arose in making zinc-finger nucleases. Disadvantage: Research regarding TALENs is still very preliminary. There is no doubt that there is a lot of potential in this technology, but the technology is not developed and practical yet. Ultimately, both types of nucleases accomplish the same task. Scientists are able to use these nucleases to make the exact change they want to any gene by inducing a double stranded break, allowing the cell to repair the DNA by either nonhomologous end joining or homologous recombination. There are some drawbacks in that some desired nucleases are difficult to make, but nonetheless, this technology is very promising. What is a nuclease? How do they work? A nuclease is an enzyme that cleaves DNA by breaking phosphodiester bonds What is an engineered nuclease? An engineered nuclease is simply a nuclease that has been programmed artificially to cut DNA at specific sites. To understand how they work we must take a closer look at DNA... What are engineered nucleases used for? Currently, studies are being done with engineered nucleases to treat HIV. Zinc finger nucleases are used to delete a specific gene in patients' CD4+T cells.
When the edit is successful, there are promising results. The "door" through which HIV enters the cell (CCR5 co-receptor) is disrupted. This means that HIV is no longer allowed to spread and affect the immune system.
Eventually, researchers hope to use this technology in blood stem cells to correct for inherited immune deficiencies.
Engineered nucleases also play a large role in research, especially gene knock-out. Gene knock-out involves deletion or alteration of a gene to observe its effect on the organism. By doing so, researchers are able to determine the role of the gene in the function of the organism and its importance to the organism's survival.
As a technologically un-savvy person, it is much like taking out one component of a car to see if it runs properly and thus determining its effect on the car as an entity. The effect might be minimal such as the malfunction of a headlight or it might be enormous like the breakdown of an engine. This is no different than the method researchers use engineered nucleases to determine the role of particular sequences in genes. Ethical issues associated with engineered nucleases Like all genetic technologies, there are many ethical concerns associated with gene editing using engineered nucleases.
It's true that this technology will be able to treat many diseases like HIV and other inherited diseases, but there is concern over the use of nucleases for editing genes to enhancing human qualities like intelligence, appearance and ability. There is a thin line between curing and enhancing. If everyone could choose their children's genes, we would essentially be left with a society of non-genetically diverse people. This is harmful to our genetic continuity due to lack of genetic variance.
Not only is there a biological issue, but a society of genetically equal people will cause a lot of conflict. If everyone thinks that they're entitled to more (more money, better careers, more power), there will no doubt be a lot of internal conflict
Also, the largest concern might just be the inherent belief that we were born the way we were meant to be. A career in genetics Generally, students aspiring to be genetic researchers should study biology, math, chemistry and physics in high school and college/university. It is very common for students to major in biology or genetics in college.
After undergraduate studies, students should pursue a Ph.D. program in genetics. After obtaining a Ph.D. most graduates will do post-doctorate studies in a university laboratory.
Then finally, the individual would be able to obtain a faculty position and conduct their own research or obtain a research position with a large biotechnology firm.