Going 26 and have achieved..... nothing.
Saturday, 26 April 2014
Name : Nurul Atiqah Burhanuddin
ID : 42823133
Tutor : DU
In present time, scientist could eliminate genetic disease in embryos by carrying out Pre-implantation Genetic Diagnosis (PGD). PGD is applicable in both cases; single-gene disorders and chromosomal disorders. Mutation occurs at chromosomal stage might happen numerically (i.e. aneuploidy) or structurally (i.e. inversions or translocations) .Initially, the embryo is cultured by in vitro fertilization (IVF) (Dickens, 2004). One cell is taken right after the embryo has reached eight-cell stage on day 3 (Spar, 2006). The remaining cells are let to be cultured in order to replace the missing cells. The extracted cells are being scanned for any genetic faults using Polymerase Chain Reaction (PCR) (A. Taei Et Al., 2010 ; Huxman,2003). When the genetic disease is detected, the non-infected DNA is transferred on the uterus wall in hope of normal baby would be born (Huxman,2003).
Scientists are concern about the arising of babies with requested traits. Designing newborn babies is a new field in which we could modify any desired genetic contained in embryo before being implanted on the uterus wall. The new technic of Zinc Finger Nucleases (ZFN) is found to allow editing or cutting out the gene at specific target. ZFN is the custom-made protein which is made up of Zinc Finger Protein (ZFP) and FokI. FokI is the type IIs restriction endonuclease originated from a bacteria called Flavobacterium okeanokoites. The FokI consists of two domain sites which are N-terminal (non-specified) and C-terminal (specified). The ZFP cleaves with the unspecified domain site of the FokI while the specified domain recognizes the DNA binding domain and designed to mark and break the double-helix strand of DNA. As a result, it stimulates the cell’s natural DNA-repair processes.
Figure 1 : Zinc Finger Nucleases binding to DNA
This technology is then makes use of the DNA repair process to alter the sequence in order to produce a new undamaged DNA by homology-directed repair of the DNA. The alteration is achievable by introducing the external DNA template repair. It would then replace the targeted gene and permanently alter the genome structure by insertion or deletion of mutation ( Durau, et. al., 2005).
Figure 2 : ZFN induce DSB and new genes being integrated into it
A case is proven to be successful when The Medical College of Wisconsin in Milwaukee, Sangamo Biosciences had carried out the ZFN method on eukaryotic cells of a mice via microinjection in its embryo. It happened to delete a gene which gives rise to the fluorescent colour of the mice’s body (Sigma, 2009). The limitation of the ZFN is the flexibility to bind to different site of DNA. It is highly depends on the sequence designed in the laboratories. A lot of researches need to be done in order for ZFN to cleave to any site on the desired DNA segment ( Durau, et. al., 2005).
Figure 3 : An example on how ZFN works
Genetic modification is an advance in science and should not be rejected entirely. Based on transhumanist, it is a great opportunity to upgrade human conditions and as part of human’s revolution in regards with the advancement of technology (Bostrom,2003). However, human is a complex creature. Scientists have to consider numerous unknown side effects in contemplating to design a baby. A study on mice had shown that even the genetic at running maize is improvised, but the adverse effect is the mice experienced hyper-sensitivity to pain. This is because multiple genes which are hard to unravel are responsible to confer one particular trait. Therefore, even genes are modified wholly according to the desired genes, the child traits are still in ambiguity (Steinbock,2008).
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Geurts. A. et. al. 2009. Knockout rats Produced via Embryo Microinjection of Designed Zinc Finger Nucleases. Science. Available at : <http://www.youtube.com/watch?v=FEHDGeKMaqY&feature=player_embedded>. [Accesses 18 April 2012].