Gnetic Fingerprinting

Question 1

What are VNTRs?

Answer 1

Variable number tandem repeats are regions of base sequences which done code for proteins and repeat many times next to one another.

Probability of two individuals having the same VNTR is highly unlikely so can be compared to identify individuals

Question 2

Describe the amplification stage of genetic fingerprinting.

Answer 2

PCR is used to make fragments from a DNA sample e.g saliva, blood
- primers are used to bind to either side of the repeats so whole repeat is amplified.
- produces DNA fragments where the length in nucleotides corresponds to the number of repeats a person has in a specific position
- fluorescent tag added to primer so can be viewed under uv light

Question 3

How are DNA fragments separated?

Answer 3

By gel electrophoresis
- placed in well in slab of gel covered in buffer solution which conducts electricity
- electrical current passed through and DNA fragments move towards positive electrode.

Shorter fragments travel further and faster, fragments are separated according to length so pattern of bands produced in the gel

Question 5

How is the length of VNTRs determined?

Answer 5

After gel has run long enough, equipment turned off and gel is placed under UV light to observe bands.

DNA ladder can be added to one well which is a mixture of DNA fragments of known lengths
- allows to work out lungs of other bands in the gel by comparing distance travelled.

Question 6

What are the uses of genetic fingerprinting? (5)

Answer 6

• determining genetic relationships
• determining genetic variation in a population
• forensic science
• medical diagnosis
• animal and plant breeding