PCR

1. PCR Dr. Ahmed EL Tahir May, 2007

2. Polymerase Chain Reaction (PCR) Develop In 1983 by Kary�Mullis. He was awarded the Nobel prize for chemistry in 1993. Just Imagine A technology enabling us to extract a tiny quantity of DNA from a single hair or drop of blood at the scene of a crime and increase the amount of it a million times. A technology allowing us to analyse the DNA from a bacterial or viral infection in order to diagnose an illness. A technology that makes it possible to mass-produce DNA from fossil remains, extinct for millions of years

3. How does PCR work Different stages of DNA replication. Use Thermus aquaticus Different temperatures. Stages: Denaturation Annealing Elongation

8. Some use of PCR: Infection detection. Amplifying the genetic material from a single bacterium or virus can provide a speedy and accurate diagnosis for serious infections such as AIDS, viral meningitis and TB, where getting the right treatment quickly can mean the difference between life and death. What is more, PCR makes it possible to identify new pathogens at a speed which would have been unimaginable a few years ago. The rapid identification of the Sars virus is one very recent example of the way PCR can help fight infections.

9. Genetic screening PCR makes it easier to identify individuals who carry genes which can cause problems like cystic fibrosis and muscular dystrophy. It has also made it possible to look at the genetic material taken from a single cell of a very early embryo during in vitro fertilisation, amplify it and identify potential problems relatively easily. In future, screens may even be developed for the genetic variations which give us an increased risk of developing problems such as heart disease or high blood pressure. This would allow people to alter their lifestyle to reduce their risk. Screening may also indicate whether a particular medicine is the best one for that person - this idea is called "personalised medicines."

10. Cancer warning cancers develop when small changes in the DNA of a cell mean that it loses the normal control of the cell cycle and grows and divides far too rapidly. Amplifying the DNA using PCR gives doctors and scientists the opportunity to pick up these genetic changes in cancerous cells early in the development of the disease. The earlier cancers are detected the greater the likelihood that they can be successfully treated. Diagnosis of bowel cancer often involves an investigation of the colon and tissue samples being taken from any areas which look suspicious. Using PCR, bowel cancer can now be detected from the DNA of cells shed in the faeces.

11. Tissue matching In organ transplants, a close tissue match between the donor and the recipient reduces the chances that the new organ will be rejected. In the past this matching has been based on blood groupings and a few other major tissue markers. PCR will lead to increasingly sophisticated levels of tissue matching at the DNA level, as a DNA bank of all the people needing transplants can be built up and PCR enables analysis of a potential donor�s tissue to be carried out quickly and effectively. This in turn should lead to more successful transplants.

12. PCR and the fight against crime: Violent crimes such as murder, although rare, leave a lasting legacy. Someone loses their life, and their family has to live with the loss for the rest of their lives. Rapes and sexual assaults leave victims with mental scars which will last longer than any physical damage. Over the years many people have been brought to justice for crimes like these � but not all of them. There are people walking about in the early 21st century living apparently normal lives who committed terrible crimes 15, 20 or more years ago. But the development of PCR and its use by police forces around the world means that some people who must have thought they had �got away with it� are now being brought to justice. Police forces are looking back over old, unsolved cases, bringing out old evidence of semen stains, blood stains, cigarette butts ... DNA has proved to be a tough molecule which survives for years. PCR means the smallest traces of DNA can be amplified to provide enough for scientists to produce a DNA fingerprint.

13. Question 1 What do the initials PCR stand for? a) polymerised chain reading b) polymerase chain reaction c) polymer counting reaction d) polymerase chain reading  Question 2 Who invented PCR? a)Francis Crick b)James Watson c)Charles Darwin d)Kary B Mullis  Question 3 For what specific purpose is PCR used? a)to amplify DNA b)to magnify DNA c)to analyse DNA d)to sequence DNA

14. Question 4 Which of the following best describes the mixture placed in a PCR vial at the beginning of the PCR procedure? a)the original DNA sample, DNA polymerase, fluorescent-tagged bases and buffer solution b)the original DNA sample, endonucleases, the four nucleotide bases and primers c)the original DNA sample, DNA polymerase, the four nucleotide bases and primers d)the original DNA sample, DNA polymerase, adenine, thymine, cytosine and guanine Question 5 The first stage of the PCR process is carried out at 90-95oC for 30 seconds. What happens to the DNA at this temperature? a)the DNA strands separate b)the primers bind to the single DNA strands c)DNA polymerase adds bases to the primer segments to build up complimentary strands of DNA d)the PCR process repeats itself Question 6 What is the optimum temperature for the enzyme DNA polymerase used in the PCR process? a)40oC b)55oC c)75oC d)90oC

15. Question 7 The three main stages of the PCR process are usually repeated around 30 times over several hours. Approximately how many copies of the original DNA molecule are made during that time? a)100 000 b)1 000 000 c)10 000 000 d)1 000 000 000 Question 8 The development of PCR has had a major impact on a number of different areas. It has led to some major developments in medicine and forensic science, some of which are still in the early stages. Which of the following technologies does NOT rely on the PCR reaction? a)detecting infective organisms using DNA b)amplifying tiny fragments of DNA for analysis in the detection of crime c)identifying cancerous changes in cells before the cancer has grown and become incurable d)DNA fingerprinting