Westlakes Science Park- Genetics Department Visit
On Wednesday 21st of April I visited Westlakes Science Park to find out more about its genetics department and what it does. Westlakes is a research institute and it does research into many things to do with environmental sciences and health as well as other things. Westlakes does research and industrial consultancy for bigger businesses. Westlakes has many different sections and the part that I visited was the genetics department which does both the research and the consultancy. Its research is into sensitivity to radiation which is the variation in how much radiation affects different people. Its consultancy is for BNFL this is the radiation effects on workers that have worked there and retired, that are working there now and the offspring of workers to find out if radiation on workers affects their offspring. The two aspects of genetics that they use are cytogenetics and molecular genetics and this report is for AS level students.
Cytogenetics is the microscopic analysis of changes to chromosomes; they are a good biological marker as radiation affects chromosomes quite easily and leaves pretty obvious effects. Westlakes genetics department studies damages in workers exposed to radiation at work for BNFL. It has examined blood samples, blood lymphocytes or white blood cells from workers at Sellafield for many years. The blood samples are taken and placed in a culture medium and cultured for 48 hours at 37oC in a 5% carbon dioxide incubator. Cells that are in metaphase are taken and slides prepared for microscope analysis. Staining techniques are applied to the samples to determine the number of chromosome aberrations.
One form of staining is the solid staining technique which lets you see how many unstable chromosome aberrations there are but it is impossible to identify which chromosomes they came from. This staining technique is a good way to find out whether someone has had a recent exposure to radiation but it is ineffective to find out about radiation over long periods of time because the cells that contain the unstable chromosome aberrations cannot undergo repeated cell division and therefore they are not discovered in this method.
Another sort of staining is Fluorescence in situ hybridisation technique (FISH) or chromosome painting. This is where individual chromosomes are ‘painted’ and pan-centromeric DNA probes are used when the cell is in metaphase so that it is possible to not only see what you could see with solid staining but it is possible to see which chromosomes aberrated so you could detect aberrations such as translocations and the stable equivalents of dicentics. Cells with translocation aberrations are able to go through repeated cell divisions so over time they could accumulate unlike other aberration so translocations are a good indicator for chronic or historic exposure to radiation and when it compared number of translocations with recorded occupational dose for retired Sellafield workers the genetics department found a positive relationship between them. The FISH is limited because at Westlakes they only use it on a few of the many chromosomes in each cell so it is not used to its full extent
Chromosomal Radiosensitivity and the G2 Assay
It is now known that different people are more sensitive to radiation than other people are because of genetically determined differences in people’s ability to identify and repair DNA damages. Also it has been suggested that people who are genetically susceptible to cancer are more chromosomally radiosensitive, basically they would show more damage if exposed to radiation than people that have a normal radiosensitivity would. Because reports have linked the two it has been suggested that cellular Radiosensitivity could be used to indicate the chance of developing cancer in the normal population.
Westlakes uses the G2 assay to study the suggestion about radiosensitivity. The G2 assay irradiates the peripheral blood lymphocytes in vitro during the G2 stage of the cell replication cycle to damage the DNA. The cells are then left to reach metaphase and they are then stained using solid staining as I told you about earlier so that when looked at under a microscope the DNA damage that was not repaired shows as chromatid gaps of breaks. A chromatid gap is a missing section in a chromatid arm that is wider than the width of the chromatid and a chromatid break is when the remaining chromatid piece becomes bent or misaligned.
More chromosomal radiosensitivity has been demonstrated in blood lymphocytes from a lot of cancer patients. Around 40% of breast cancer patients had increased chromosomal radiosensitivity whereas the healthy control group was only 6% and similar independent studies have had similar results. Westlakes genetics department is currently studying to examine relationships between cancer predisposition and radiosensitivity by finding out whether the survivors of childhood cancer have higher radiosensitivity in comparison to a control population of the same sort of age.
There are ethical issues involved in radiosensitivity because if managers at industries like Sellafield could find out if prospective workers are more probable to be susceptible to cancer they would be much less likely to let them do a job where they would be likely to be exposed to much radiation. They would be placed somewhere where there is less radiation. This is an ethical problem because it means that people might not be able to apply for the jobs that they want to which would mean that people have less choice for what to do. Also insurance for the worker would be much higher because they are known to be more likely to get cancer than most others.
Ionising radiation and affects on offspring of the exposed
The genetics department at Westlakes looks at the effects of ionising radiation on the offspring of people who have been exposed to it by comparing the DNA from the mother and the father with the child’s to see if any mutations have occurred in the child. This is done using minisatellites, gel electrophoresis and PCR (polymerase chain reaction). The method for this is to take a blood sample from the mother, the father and the offspring and then extract to DNA from the blood, then make sure that you are dealing with blood related family from all parts, this is by minisatellite loci which is basically DNA fingerprinting but using single locus rather than multilocus probes.
PCR is now used, PCR is just the production of more of a persons DNA from a small sample of DNA. Once the PCR is done the alleles from the parents and offspring are compared with gel electrophoresis and then use Southern Blotting to compare the offspring with the parents and if there is a mutation the offspring doesn’t quite match up with either parent at one point. Despite all of the research into this so far no genetic mutations have been found in any of the offspring at all.
Sources for most pictures are a handout that we were given on the visit with one of the pictures from a website stated on the picture and the diagram on the left hand side of the last page was drawn by me in Microsoft Word.