Minutes of the 338th meeting held at 10.00 in Stokesley Town Hall on Tuesday 19th January 2016
Speaker – Dr. Alex Dellipiani ‘Origins and Genes’
Alex studied medicine at Edinburgh University. He moved to Stockton in 1968 and worked at
North Tees Hospital as a consultant gastroenterologist. He has been retired for 20 years and
has lectured at Newcastle University. He is a member of Stockton Probus.
Alex talked about genes in the context of evolution. Anthropology, geology and carbon
dating all provide valuable information. Approximately 4.6 million years ago, the first
mammals to walk on two legs evolved. At the same time, their brains began to enlarge.
The earliest species to resemble us was Homo Erectus who first existed 2 million years ago.
He knew about hunting, fire, complex stone tools, campsites and he looked after the weak in
his society. He moved out of Africa into the northern hemisphere 500,000 years ago.
Neanderthal man, found in Europe between 300,000 and 30,000 years ago, coexisted with
Homo Sapiens. He buried his dead and used grave goods. We do not know why he died out.
Genetics has made it clear that we came from Africa independently of Homo Erectus about
80,000 years ago. Climate change appears to have been very important in early human
migration. Man arrived in Australia 60,000 and in Latin America 10,000 years ago.
The study of how changes develop occurred in several places in the 19th century. As well as
Darwin, Lamark, a French scientist and Mendel, an Austrian monk wrote papers on
evolution. It was not until the 1900s that genes, cells and DNA were understood.
The human body has trillions of cells. A red blood cell has a life of about 3 months, but brain
cells are never replaced. The nucleus of all cells contains DNA and chromosomes. Crick and
Watson won Nobel prizes for their discovery of the double helix structure of DNA.
The helical strands have paired bases between them. There are 4 types of base: A, C, T &
G. The order of these is the genetic code. Every cell in chromosomes is paired with one from
the father and one from the mother. The human has 23 pairs.
Genes make us who we are. They define the proteins which in combinations are unique to
each individual. They also pass on information to the next generation. They also monitor the
cells in which they exist and determine the sex of the organism.
When the human genome was decoded, there were far fewer genes than expected and only
about 3% of these make us who we are. 40% of genes control the others. Genetic diseases
eg cancer are normally caused by problems with these, rather than the 3% which define us.
Stem cells may develop into muscle, red blood cells or nerves for example. They can be
harvested from the liver and bone marrow and used to repair the body in some cases.
Mature cells can be encouraged to act as stem cells as was the case with Dolly the sheep.
The influence of the environment on development was seen when a moth in London
replaced its black spots with white in a short time after the Clean Air Act was passed. The
response of foetuses to the Dutch famine in 1944 was seen in following generations too.
In reply to questions, Alex said that progress in treatment for MS had been slow because
drug companies had not seen this as a route to profit. He explained that Alzheimer’s was
caused by too much protein being deposited in brain cells. There might be a cure, but
vascular dementia, caused by inadequate blood supply looked more difficult to treat. Alex
said the idea that we are descended from very few women is almost certainly oversimplified.