From peas to drugs: What to expect from the new Genetic Engineering Unit

On Monday we begin the Genetics and Genetic Engineering Unit for Y13 BTEC students in the innovation labs. The unit comprises two halves: classical genetics as defined conceptually by Gregor Mendel using Pisum sativum (left) as his model organism. This was later given a physical basis by a number of scientists scientists in the USA, including, Morgan, Beadle and Tatum and others, and in molecular terms in the post war years (WWII) by Watson, Crick and Brenner to name but a few illustrious players! There is a nice timeline here. By the end of the 1960s, scientists knew that Mendel's ideas on inheritance could be explained by the genotype as conveyed by DNA, which passed on the phenotype through RNA and proteins and which was replicated by the process of semi-conservative replication. The latter discovery was a result of key experimental work by Arthur Kornberg and Matt Meselson and Frank Stahl. You can read all about 
these landmark experiments by following the links attached to their names. The flow of information from genotype to phenotype is often referred to as the central dogma of Molecular Biology. You must familiarise yourselves with this concept and the molecular basis of it.

The key to understanding Darwinian evolution, is an appreciation of the  intrinsically low, but finite levels of mutation that accompany cell division. The replication machinery of human cells is extremely accurate (we refer to this as high fidelity), but is not perfect. In addition mechanisms exist for genetic exchange as chromosomes "cross over", that is, closely related DNA sequences often swap over as chromosomes prepare for separation during meiosis in sexually reproducing organisms. Finally, there are a group of genetic elements that jump around the genome and insert, semi randomly: these are referred to as transposable elements. Again, these genetic elements can facilitate genetic diversity, as first discovered by Barbara McClintock in maize (top RHS). You will be given a grounding in the key concepts of genetics by Mr. Houseman and his team during the Unit.

As the fundamental knowledge of genetics shifted towards more molecular ideas during the 1950s and 1960s, several bacterial geneticists exploring the mechanisms of plasmid replication and eukaryotic genes, including Stanley Cohen, Herb Boyer and Paul Berg in California, together with a Swiss microbiologist, Werner Arber, a giant of a New Yorker, Hamilton (Ham) Smith and Dan Nathans on the East Coast of the USA, brought their knowledge of restriction enzymes to facilitate the construction of the first organism (Escherichia coli) harbouring foreign DNA. Thus was born molecular cloning, recombinant DNA technology, or more simply, Genetic Engineering. They managed to obtain genetic material from one organism, splice it into a "cloning vector" (a plasmid) and transform E. coli, thereby changing its genotype and its phenotype. These landmark experiments not only earned most of the scientists the Nobel Prize, but paved the way for the first Genetic Engineering company: Genentech (Genetic Engineering Technology) which remains one of the world's most successful drug company's (now as part of Roche), using genetic engineering technology to produce new medicines.

Mendel's ideas are at the heart of all contemporary Genetic Engineering. The difference between Genetics and Genetic Engineering is simply that in the latter, we are attempting to create new combinations of genes and genetic elements in order to produce a novel organism or gene product (either a protein or an RNA). Since the first recombinant DNA molecules were described in the 1970s, there have been many improvements in the strategies and methods for cloning genes. However, despite these modification, the basic principles remain the same. The introduction of the Polymerase Chain Reaction in the 1980s revolutionised Molecular cloning, so much so that it is probably one of the most common techniques in any research or diagnostic laboratory today. It is also one of the few techniques in Life Sciences that crosses the disciplinary boundaries. I have seen PCR instruments in Chemistry, Physics and Archaeology Departments!

During the first session in the lab we shall use agarose gel electrophoresis combined with a set of restriction enzymes to analyse the genome of the simple bacteriophage lambda. This will be combined with your experience from last year in basic bioinformatics to gain an appreciation of the experimental basis of Genetic Engineering and to compare the information deposited in the NCBI data bases with experimentally obtained "restriction mapping". Thanks to New England Biolabs, we not only have access to a selection of restriction enzymes, but we shall use their online suite of software tools to explore the results further. The experiments will be covered in more detail in microblog here, over the next few weeks.

The second phase of work will involve an introduction to the elements of PCR. This will include an explanation of the exponential phase of amplification together with the principles of primer design. From past experience, everyone will get this wrong, before you get it right! PCR relies on the availability of heat stable (thermostable) DNA Polymerases, and the application of the complementary base pairing described so elegantly by Watson and Crick over 60 years ago! You should refresh your knowledge of the molecular properties of DNA here. This will also be covered in class. I am most grateful to Bioline for their support of the laboratory work, they have provided us with samples of their Taq polymerase "master-mixes" in order that we can demonstrate PCR using primers from my own research lab. I am really looking forward to the unit: it is a close second favourite to Biochemistry!  The combination of Biochemistry and Genetics, or Molecular Biology, and its application in the form of Genetic Engineering, or as it is often now called Synthetic Biology is widely perceived to be one of the most vibrant areas in the Life Sciences today.