DNA Fingerprinting The Truth is Out There. 1. What is DNA Profiling? A technique used by scientists to distinguish between individuals of the same species.

DNA FingerprintingThe Truth is Out There

1. What is DNA Profiling?

A technique used by scientists to distinguish between individuals of the same species using

only samples of their DNA

2. Who Invented it?

a. The process of DNA fingerprinting was invented by Alec Jeffreys at the University of Leicester in 1985.

b. He was knighted in 1994.

3. Why is DNA profiling useful?

a. All living things have DNA

b. The nucleotide sequence is unique to all individuals (except identical twins.)

4. Stages of DNA Profiling

a. Stage 1:i. Cells are broken down to release DNA

ii. If only a small amount of DNA is available it can be amplified using the polymerase chain reaction (PCR)

4. Stages of DNA Profiling b. Step 2:i. The DNA is cut into fragments using restriction enzymes.

ii.Each restriction enzyme cuts DNA at a specific base sequence.

4. Stages of DNA Profiling

iii. The sections of DNA that are cut out are called restriction fragments.

iv. This yields thousands of restriction fragments of all different sizes because the base sequences being cut may be far apart (long fragment) or close together (short fragment).

4. Stages of DNA Profiling

e. Stage 3:i. Fragments are

separated on the basis of size using a process called gel electrophoresis.

ii. DNA fragments are injected into wells and an electric current is applied along the gel.

4. Stages of DNA Profiling

iii. DNA is negatively charged so it is attracted to the positive end of the gel.iv. The shorter DNA fragments move faster than the longer fragments. v. DNA is separated on basis of size.

4. Stages of DNA Profiling

vi. A radioactive material is added which

combines with the DNA fragments to produce a fluorescent image.v. A photographic copy of

the DNA bands is obtained.

5. Uses of DNA Profiling

a. DNA profiling is used to solve crimes and medical problems

6. Crime

a. Forensic science is the use of scientific knowledge in legal situations.

b. The DNA profile of each individual is highly specific.

c. The chances of two people having exactly the same DNA profile is 30 million to 1 (except for identical twins).

7. Biological materials used for DNA profiling

a. Bloodb. Hairc. Salivad. Semene. Body tissue cellsf. Most other body fluids

8. DNA Profiling can solve crimes

a. The pattern of the DNA profile is then compared with those of the victim and the suspect.

b. If the profile matches the suspect it provides strong evidence that the suspect was present at the crime scene (NB:it does not prove they committed the crime).

c. If the profile doesn’t match the suspect then that suspect may be eliminated from the enquiry.

9. Example

a. A violent murder occurred. b. The forensics team retrieved a blood sample

from the crime scene. c. They prepared DNA profiles of the blood

sample, the victim and a suspect as follows:

10. Was the suspect at the crime scene?

11. Solving Medical Problems

a. DNA profiles can be used to determine whether a particular person is the parent of a child.

b. A childs paternity (father) and maternity(mother) can be determined.

c. This information can be used ind. Paternity suitse. Inheritance casesf. Immigration cases

Is this man the father of the child?

Mother Child Man

12. Famous cases

a. In 2009 Howard Stern claimed to be the father of the late Anna Nicole Smith’s baby girl. This turned out to be a paternal and an inheritance issue. Stern was found NOT to be the father.

12. Famous Cases

a. Colin Pitchfork was the first criminal caught based on DNA fingerprinting evidence.

b. He was arrested in 1986 for the rape and murder of two girls and was sentenced in 1988.

12. Famous Cases

a. O.J. Simpson was cleared of a double murder charge in 1994 which relied heavily on DNA evidence.

b. This case highlighted lab difficulties.

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