6.3.3(DNA profiling)

Describe what is meant by tandem repeats

• They are repetitive segments of DNA that do not code for proteins

Describe what is meant by DNA profiling

• It is the comparison of the number of times a sequence is repeated and the different places it is repeated in an individuals genomes

Describe how DNA can be profiled

1. DNA is obtained from the individual

2. The DNA is then digested using restriction enzymes for known STRs

3. This forms DNA fragments where the length corresponds to the number of repeats the person has at each specific position

4. A fluorescent tag is added to all the DNA fragments so they can be viewed under UV light

5. The DNA fragments undergo electrophoresis and then bands form which are able to be analysed

Name 3 applications of DNA profiling

• Forensic science

• Maternity and paternity

• Analysis of disease

Describe how DNA profiling can be used in forensic science

• DNA profiles of the suspect and DNA found at the crime scene can be compared

• If both profiles have a band at the same location on the gel it means

• They have the same number of nucleotides and so same number of sequence repeats

Describe how DNA profiling is used to determine paternity and maternity

• By comparing the DNA profile of the child, the mother and the father

• Half of the STR should be the same as the father and half should be the same as the mother

• The more bands which match on the DNA profile, the more genetically similar they are

Describe how DNA profiling can be used to analyse disease

• Protein electrophoresis can detect the type of haemoglobin and aid diagnosis of diseases such as sickle cell anaemia

• A varying number of STR for a condition can be detected by electrophoresis