Transforming human lives

Dr Senarath TENNAKOON

By means of artificial cloning it is possible to create an organism that is an exact copy of another - an identical twin. So the original animal and its clone share every segment of their DNA. Cloning has widespread uses in biology. In medicine stem cells could be generated. With the creation of Dolly in February 1997 some predictions in fiction became a reality. It also raised interest over the ethical, moral and legal issues pertaining to the cloning of human beings.

Dolly was born in the Roslin Institute, UK, near Edinburgh on July 5, 1996 and became a global celebrity. Dolly was cloned from an adult cell DNA. But Dolly developed breathing problems and a cough that led to her death in February 2003. An autopsy revealed that Dolly had a lung tumour. Maverick scientists often claim that the work on Dolly and other animals has paved the way for cloning human beings. But to repeat Dolly’s experience in human beings would lead to the emotional turmoil of failed pregnancies, miscarriages and deformed fetuses causing immense misery.

There are also concerns pertaining to the psychological and social impacts on any child created by cloning. As such cloning human beings would be utterly irresponsible.

The German philosopher and biologist Hans Driesch (1867-1941) was the first to create twins in 1891, from a two cell sea urchin embryo by the simple act of their separation. This act disproved the widely respected views of the eminent German biologist August Weismann (1834-1914), that such an act would create half the original creature. Driesch’s research showed that embryonic cells retain the potential to turn into any cell type.

The German embryologist Hans Spemann (1869-1941) was the pioneer in the cloning method by nuclear transfer. He used baby hair for this purpose as a loop to constrict the egg. Thus he created two salamanders. Later in the 1950s John Gurdon at the Oxford University produced 30 little albino frogs from the cells of a single little albino tadpole. In 1986 Steen Willadsen used nuclear transfer to clone sheep, from early embryos. Later he produced calves from 128 cell embryos which contained two cell types.

Nuclear transfer has opened the secrets in cloning. It is possible to create rare and elite animals - wild cats, wild ox and pet animals. Further nuclear transfer has become popular as a therapeutic cloning methodology.

An alternative to therapeutic cloning is also becoming popular. Here, instead of using DNA for nuclear transfer, pluripotent stem cells are used and does not need human eggs. Sinya Yamanka of Japan has developed this method and is useful in repairing damaged hearts, treating Parkinson’s disease and Motor Neuron disease.

Generally we are unaware of the potentials of our genetic make up (genotype). But the genetic make up could contribute to several conditions such as Diabetes and heart disease. But we are generally aware of the environmental factors that also contribute to disease as well as good health.

These factors are within human control, unlike the genetic factors. In the case of diabetes and heart disease for example, a sensible healthy diet increases our chances of reaching a ripe old age. Medical Genetics is becoming crucial in guiding the ways of life of people with genetic disorders as well as in guiding those at risk of passing such diseases to the progeny and how to prevent them.

According to one study there are over 4000 inherited diseases caused by genetic defects. Gene therapy is yet another method of adding normal genes to a person’s defective genotype or repairing the faulty genes themselves. Gene insertion by physical methods as well as via viral agents is being experimented. Some disorders which might be suitable for gene therapy are:

Haematopoetic such as haemoglobinopathies, hepatic like Alfa 1 antitripsin deficiency, metabolic like phenylketourea, oncogenic like brain tumours endocrine like diabetes and respiratory like cystic fibrosis. In Thalassaemia using gene therapy, the normal human gene for haemoglobin synthesis is inserted into a virus which is then used to infect a culture of bone marrow cells taken from the patient.

Screening the bone marrow cells identifies the cells with the normal haemoglobin gene inserted. These modified cells are returned to the patient (Kingston 1994).

The role of biotechnology and genetic engineering for improving the quality of human life by way of improving nutrition, controlling disease and preventing early death cannot be underestimated. Biotechnology uses mirooraganisms, plant cells and animal cells on a large scale for the production of commercially important products. The use of moulds to make cheese, bacteria to make vinegar and yeast to make bread, beer and wine are known examples.

Genetic engineering is essentially the science of manipulating genes to our advantage. It is now possible to manipulate genes to create organisms with special characteristics for producing foods, medicines and industrial chemicals. Before 1980, insulin for treating diabetes was obtained from slaughtered cattle and pigs. But in 1980 Genentech, a Californian company specialized in genetic engineering, isolated the genes that code for the A and B polypeptide chains of human insulin, spliced them into a bacterial DNA called a plasmid and inserted the modified plasmid into the bacterium Escherichia coli and thus genetically engineered it to produce human insulin. This insulin is identical to the insulin present in human beings.

People are interested in knowing their genetic roots and in America they purchase genetic kits from one of the 40 companies that promote the finding of distant relatives. Most tests trace ones paternal and maternal lines by examining genetic markers on the mitochondrial DNA which is passed from mother to child or on the Y chromosome passed from father to son. By tests on the 22 pairs of non sex chromosomes, the race of the individual could be studied; whether European African, Asian or Native American.

The human genome project has revealed that we have around 23000 genes. Each gene often codes for more than one protein Instead of having two copies of every gene, one from each parent, we often have one or three or more as a result of chunks of DNA being lost or duplicated. This helps to explain variations among individuals. It is useful to know ones genome for the sake of safety, better health and development. For instance ‘Monica’ who had her DNA profiled was able to tell her doctors that she was oversensitive to the blood thinning drug warfarin, when she developed a blood clot after a long flight.

Many people with an african or asian ancestry are less sensitive to the anti clotting drug clopidogrel as their enzyme CYP2C19 have variations.

As a result they need an alternate drug or need higher doses of clopidogrel. About a third of breast cancer patients have an overproduction of their HER protein which can be treated with an antibody called transtuzumab (Herceptin) that blocks HER’s effect. (New Scientist, 19 June 2010).