DNA profiling Flashcards
Define a DNA profile
A DNA profile is a method of making a unique pattern of bands from the DNA of a person, which can them be used to compare with the DNA profile of another person
How many steps does the method of preparing a DNA profile consist of?
4
Briefly list the 4 steps of the method of preparing a DNA profile
- The DNA id released from cells
- The DNA is cut into fragments
- The DNA fragments are separated according to their sizes
- The patterns produced by the fragments are compared or analyzed.
In order to produce a DNA profile, cells must do what?
They are broken down to release their DNA
What are the headings of the 4 steps of DNA profiling?
- DNA is released
- DNA is cut into fragments
- The fragments are separated
- Patterns are compared
Explain the 2nd step of DNA profiling (3)
DNA is cut into fragments:
1. The isolated DNA is cut into fragments using special enzymes called restriction enzymes.
2. Different restriction enzymes will cut DNA at specific base sequences.
3. The sections of DNA cut will be of different lengths because the base sequences being cut may be close together or far apart on the DNA strands
What is used to cut DNA into fragments?
restriction enzymes
Where were restriction enzymes first isolated from?
They were first isolated from bacteria
What is the use of restriction enzymes in bacteria?
They are used to destroy the DNA of invading viruses in bacteria
Explain the 3rd step of DNA profiling (7)
The fragments are separated:
1. The sections of DNA that have been cut are separated on the basis of their size.
2. They’re separated by a process called gel electrophoresis.
3. This involves placing the invisible DNA fragments in a small glass tank containing a sugar-based gel.
4. An electric current is applied along the gel.
5. The current draws the negatively charged DNA to one end of the gel.
6. In this way, bands of small fragments are separated from bands of larger fragments.
7. When the electrophoresis is finished a permanent record of results is obtained. (this may involve adding radioactive material to produce a fluorescent image) A photographic copy of the final pattern of DNA is then obtained.
Explain gel electrophoresis
This involves placing the invisible DNA fragments in a small glass tank containing a sugar-based gel.
An electric current is applied along the gel.
The current draws the negatively charged DNA to one end of the gel.
In this way, bands of small fragments are separated from bands of larger fragments.
What is added to the separated DNA fragments to produce a fluorescent image?
radioactive material
What happens when radioactive material is added to separated DNA fragments?
A fluorescent image is obtained
Explain the 4th and final step of DNA profiling (2)
- It is very unlikely that two people will have the same DNA profile (unless they are identical twins).
- If the pattern of bands from 2 different DNA samples is the same, then they both came from the same person.
If the pattern of bands from 2 different DNA samples is the same, what does this most likely mean?
They came from the same person
