PCR and Gel Electrophoresis

Question 1

Name of the enzyme used in the process used to amplify the DNA in the small sample of blood taken from the crime scene.

Answer 1

Polymerase

Question 2

Name of the process that could be used

to separate DNA fragments to create the profiles

Answer 2

Electrophoresis

Question 3

How can you tell it is the suspect using DNA profiling?

Answer 3

1. Suspect matches all of the bands in the sample.
2. DNA profiling assumes every individual’s DNA is unique.
3. Apart from identical twins.
4. DNA profiling analyses the introns / noncoding
   blocks / STR / short tandem repeats.
5. Non-coding DNA very variable.
6. Large number of introns (non-coding blocks)
7. Which can result in many combinations at each locus.

Question 4

Explain why evidence from DNA profiles may not be absolutely conclusive.

Answer 4

1. DNA profiling has many stages.
2. Contamination can occurat any stage.
3. Only a small proportion of DNA is analysed.
4. Possibility of two identical profiles from
   unrelated individuals.
5. Identical twins may show the same profile.

Question 5

Suggest how DNA profiling could be useful to scientists who examine fossils of animals and plants.

Answer 5

1. Comparisons made between DNA from fossils and
other organisms.
2. To find genetic relationships.
3. Used in taxonomy.
4. To understand evolutionary lines.

Question 6

Describe how gel electrophoresis can be used to analyse DNA.

Answer 6

1. DNA sample, e.g. blood, saliva, semen ;
2. Small samples of DNA can be
   amplified by PCR
3. Use of restriction enzymes to
   break DNA ;
4. reference to use of {electro potential /
   potential difference / eq} ;
5. reference to {treatment / staining / eq} ;
6. show up as {bands / bars / eq} ;
7. reference to the {number of bands / eq} that
   match indicates similarity of the DNA ;

Question 7

Suggest how DNA analysis could give further evidence for their conclusions that apes and humans are similar.

Answer 7

1. to similarity (of DNA) indicates
   closeness of relationship ;
2. because genes are sections of DNA / eq ;
3. genes are the codes for protein