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Gene editing or more correctly, genome editing, is a form of genetic engineering that seeks to insert, delete or replace DNA from a genome of an organism using enzymes called nucleases. The latter act like “molecular scissors” and cut or cleave DNA at site-specific double stranded breaks (DSBs) at a desired location within the target DNA.
In essence, gene editing involves proteins associated with an engineered nuclease that can bind to a target DNA site (for example a faulty gene), cut out the faulty gene, and then allow a correct DNA sequence to be inserted. Such targeted gene modification is an important development in molecular biology as it has huge potential to improve drug development, gene therapy, and agriculture, as well as in the correction of genetic diseases in humans.
Three types of engineered nucleases have been identified, the last of which (CR) is the most recent:
- Zinc-finger nucleases (ZFN)
- Transcription activator-like effector nucleases (talens)
The CRISPR-Cas system, which stands for clustered, regularly interspaced, short palindromic repeats, are RNA-based bacterial defences that operate by identifying and removing DNA from bacteriophages (viruses that infect bacteria) and plasmids.
At its simplest, targeted genome cleavage has a homing/target device (guide or gRNA) and a cleavage enzyme called a nuclease (CAS nuclease). When the bacterium detects a viral DNA inside itself as a result of infection it produces two types of short RNA, one of which matches the foreign virus DNA sequence (guide RNA). These two RNAs form a complex with a nuclease protein, CAS9. The role of the guide RNA is to match with the foreign viral DNA. Once CAS9 and combined RNAs bind to the target DNA, they cut the DNA, thereby disabling the viral genome that has infected the bacterial genome.
Researchers have realised that this natural system could be engineered to cut not just viral DNA, but any DNA sequence at a precise location. This can be done by altering the guide RNA (gRNA) to match a target DNA. Correct DNA sequences can then be inserted to reverse the faulty effects of a given gene; this can be done in stem cells and inside a fertilised egg. In the UK, the government recently gave the green light for permission to use CRISPR-Cas9 technologies to modify human embryos.
Researchers are excited about the promises of this technology, but are very aware that the technique has risk, such as modifying unintended DNA sequences. Risks aside, gene editing offers a real chance to tackle genetic diseases and to make heritable changes. For example, the technique could be used to edit the genome sequence of mitochondria, which we inherit from our mothers. Mitochondria are found in eukaryotic cells and are the powerhouses of the cell as they are able to synthesise ATP. Mutations inside mitochondrial DNA are the basis of various diseases, such as myopathy and Leber’s hereditary optic neuropathy, amongst many others.
In 2015 the UK government gave the go-ahead for mitochondrial replacement therapy that allowed for the so-called “three-parent babies”, which involved using a third person’s mitochondria to replace diseased mitochondria. Gene editing techniques could be used to remove faulty DNA in mitochondria, which then becomes heritable and replaces the need for mitochondrial replacement therapy.
Like most of genetic engineering, the advanced solutions of gene editing all result from techniques used in bacteria and viruses. The tools of molecular biology and genetic engineering, restriction endonucleases, ligases, and reverse transcriptase, are enzymes used by microbes to manipulate foreign DNA. Interestingly, the CRISPR-Cas9 technique was first studied in bacteria trying to protect themselves from the impact of bacteriophages (viruses that infect bacteria). When considering the complexity of modern molecular biology, the irony that we use enzymes and proteins that evolved millions of years ago to protect bacteria from viruses is lost on most people. What is not lost on anyone, however, is the potential that genome editing and further advances will have on human disease prevention and possibly human ageing over the coming decades.
John Dalton, 2016
Head of Science, David Game College
Calling all students who are thinking about becoming vets! The Royal Veterinary College is organising a Pre-Vet Summer School for interested candidates. Students will gain vital veterinary knowledge, make new friends from around the world and experience university life.
- Earn one week of veterinary experience in the RVC’s globally recognised animal hospitals and research facilities.
- Get a taste of student life at the RVC, meeting student ambassadors and academic tutors.
- Explore London, one of the world’s most exciting cities, as well as the beautiful English countryside.
Cost: £2300 includes accommodation, all meals, social activities listed in the programme, equipment, airport transfers.
Other costs: The price does not include travel to/from the event or health insurance.
Minimum age 16
On Tuesday evening the David Game Debate Society took part in a spirited 2 hour debate on whether or not child vaccinations should be made compulsory, and finishing with a topical discussion on the merits of gentrification for our neighbourhoods.
In regard to the first debate, our team was assigned the difficult position of arguing against the motion. Responding to our opponents affirmative position that it was a matter of public safety and something that has greatly reduced deaths – we opted to argue a more libertarian approach to the subject. Highlighting the enshrined rights of members of religious groups, as well as concerned parents – who deserve to decide on their children’s safety over government imposed mandates.
The second debate involved a subject that has touched upon many raw nerves in London’s increasingly pricey housing market – gentrification of poorer neighbourhoods. David Game was assigned the position that this was a good thing for our communities – and we successfully argued the economic position and the fact it can lead to a higher standard of living, and a greater mix of people in one area. However, the opposing team touched upon the sense of nostalgia and uniqueness that has been lost in many of London’s most vibrant housing estates.
We thoroughly enjoyed the evening and welcome any prospective debaters to our club that takes place every Thursday evening from 6.30pm in room D8.
“I do not agree with what you have to say, but I’ll defend to the death your right to say it.” – Evelyn Beatrice Hall
Following a $900m class-action lawsuit settlement between the NFL and former players, heightened concern over player welfare has accelerated the introduction of measures to address concussion and head trauma.
It’s a complex issue, as the effects are often not notable until after a player has retired and is no longer and part of a franchise’s daily infrastructure. However, rather than absolve the NFL of accountability, this only serves to heighten the need for care during a player’s career.
One solution is technology such as Linx IAS, originally a military tool designed to measure the invisible impact of shockwaves from an explosive blast. The tool can give medical staff a sense of the severity of the impact of the shockwave on an individual, which in turn can help the triage process.
Keeping track of impact over time will allow coaches to remove players from the field before lasting damage is done, and is a real step forward in sports medics’ attempts to understand and address head injuries in real time.
Not only beneficial for sports players and fans alike, the developments are interesting on a number of levels. Medics may choose to explore how assessing head injuries objectively compares with subjective examination and more antiquated concussion tests, whilst Engineering applicants may wish to engage with how that technology might be put together. Lawyers, on the other hand, may like to consider the settlement that kick-started this movement – is the NFL responsible for compensating its players many years after they retire? Who should take ownership of caring for the players? In any case, embracing technology, rather than rejecting it, seems like a step in the right direction.
The Grierson Awards
Last night, the biggest names in documentary film-making got together to celebrate the best of British factual production.
The Grierson Awards have been running for 43 years and have previously championed the likes of David Attenborough, Nick Broomfield, and Banksy for their contributions to film-making. Although the awards are mainly industry facing, they offer a fantastic opportunity to highlight some of the best documentaries of the year.
The big winners this year were Grayson Perry as best presenter, The Romanians are Coming as the best series, and Virunga, a film about protecting the last mountain gorillas in Congo, won best cinema documentary. Other notable winners include Cambridge Alumni, Brian Woods, who was celebrated for his fantastic film “Curing Cancer” and Kim Longinotto who got this year’s lifetime achievement award.
Attentive Oxbridge candidates could mine these films for a wealth of engaging and relevant material to bolster their knowledge ahead of their interviews. Arch and Anth students should look to Kim Longinotto’s breath-taking collaborations with anthropologists for global insight or “The Romanians are Coming” for a contemporary example of multi-cultural Britain. Similarly History, Biology and Medical students could look to films about the First World War, species preservation, and cancer research respectively for inspiration. For the most forward thinking candidates the awards highlight how relevant academic subjects are in contemporary media and perhaps even inspire an amazing career to pursue after their degrees.
The Problem With Policy
Following decades of the ‘One Child Policy’, China has lifted this ban allowing families to now have two children. However some believe other elements of China’s family planning policies remain unchanged and restrictive. For example, single mothers do not receive educational or financial support for their child and are often fined for giving birth outside of marriage; for the city of Wuhan in 2013 this fine was $13,000. With the country’s crippling demographic problems, lifting the restrictions placed on single mothers could help the process of rejuvenation. This contrasts with Sweden who offer generous financial aid to their single parents.
Students considering Law should think about the reasoning for different family planning policies implemented in countries and the legal position of those who are negatively affected by such policies.
Those wanting to study PPE should try to understand the position of the government to put in place family planning policies and the economic reasoning for doing so.
HSPS and Geography applicants should use this case study to look at the causes and effects of demographic problems. What other solutions could be put in place to help countries with demographic issues?
Friday 30th October – Sunday 1st November
Over the course of three days at the end of the October half-term, we host our flagship Oxbridge Preparation Weekend. This residential study-course is designed to give students the most throrough preparation for their Oxbridge application, and an introduction to life at Oxbridge.
Click here to find out more about how our course can support your application and to book your place online. Our Oxbridge-graduate consultants can also fast track your booking over the phone, and are available on +44 (0)20 7499 2394.