What is the link?

Basically a DNA photocopier!

A technique for the

amplification of DNA in vitro

(outside the body – like IVF).

Learning Outcomes

• Understand the monumental impact of PCR on our world!

• Explain the process in PCR• The uses of the amplified DNA in DNA

probes• Give medical and forensic application of the

technology

• Invented by Kary B. Mullis (Nobel Prize in chemistry in 1993 for his invention of the polymerase chain reaction (PCR).

• The process, which Mullis conceptualized in 1983, partly due to a “creative” experience one weekend with an luminous racoon in the woods (for scientific discoveries – a creative leap is needed!)

• Without PCR there would be insufficient DNA for CSI/human genome project!

• It has changed our world!

PCR process

• If you wanted to amplify DNA what things would you need?

PCR process - ingredients

• DNA polymerase (duplicates DNA, Taq is from Thermus aquaticus which is found in hot springs and is thus stable at high temperatures)

• Primers x2 (piece of single stranded DNA which is complementary to the specific target sequence at the 3’ end of each DNA replicated strand) This specificity allows you to amplify any – enabling to find a needle in a haystack of DNA

• Free nucleotides to make amplified DNA• Original DNA strand needed to be replicated.

PC

R P

roce

ss S

umm

ary

– Le

arn!

PCR in pictures

• Add a diagram/picture to each stage to help you remember each stage

So it uses are ….

Forensics!

Gen

etic

test

ing

DN

A p

robe

s• DNA probes are short, single stranded

fragment of DNA that is complementary to a specific sequence (called target)

• DNA Fluorescent labelling allows detection.

DNA Arrays

• An array is a ordered arrangement• Arrays of DNA probes are used to detect the

presence of specific sequences in samples of DNA.

• Can be used in detecting the gene in Cystic Fibrosis

Medical Uses

• By screening a cell sample from a patient for;– the presence or absence of a particular sequence

(called screening)– a diagnosis of genetic disease status (BRAC1 & 2)– risk of disease onset can be made (for examples risks

of mutations and likelihood of disease)

Medical Uses

• By screening a cell sample from a patient for the presence or absence of a particular sequence, a diagnosis of disease status or risk of disease onset can be made.

• DNA profiling allows the identification of individuals through comparison of regions of the genome with highly variable numbers of repetitive sequences of DNA.

Forensic Uses

• In non-coding regions of DNA there are highly repetitive sequences, these are unique to each individual and scattered across the whole genome.

• Use this to compare DNA for patenity cases and crime scenes.

•

Forensic Uses

• DNA profiling allows the identification of individuals through comparison of regions of the genome with highly variable numbers of repetitive sequences of DNA.

Demonstrate your understanding

1. What can be produced in vitro by employing the polymerase chain reaction (PCR)?

2. In PCR, what is a primer?

3. Why is the DNA heated during the PCR process?

4. What is the purpose of cooling the DNA sample?

5. What characteristics of the DNA polymerase used in PCR prevent it from becoming denatured during the process?

Continued .....

6. Briefly describe the structure of a genetic probe.

7. What is a genetic probe used for?

8. What medical application does the amplification of DNA by PCR make possible?

9. What features of the human genome makes each individual unique and allows genetic profiles to be constructed?

Review Triangle

1 Question you still have about human genomics/ PCR/ technology

2 uses of PCR/DNA probes

3 stages or ingredients in PCR