MG (DNA Profiling)

Question 1

what is DNA profiling

Answer 1

• process where a specific DNA banding pattern, called a profile, is obtained from a person or sample of bodily tissue by using gel electrophoresis.
• Pattern can be compared

Question 2

What are tandem repeat sequences of DNA?

Answer 2

• repetitive sequences of DNA introns (non-coding)
• They all feature the same core sequence. GGGCAGGAXG (X can be any one of the 4 nucleotides).
• Lengths are highly variable -VNTRs (variable number tandem repeats)

Question 3

what are telomeres

Answer 3

hair pin structures on the end of chromosomes

Question 4

DNA Profiling Procedure

Answer 4

1. Extract DNA from sample - Can use PCR if the sample is small
2. Digest the sample – DNA cut into small fragments with restriction endonuclease
3. Separate the DNA fragments using electrophoresis.
4. Banding pattern is produced.
5. The DNA to which the individual is being compared is treated with the same restriction enzymes and is also subjected to electrophoresis
6. Banding patterns can then be compared

Question 5

Are the number of STRs the same in each person?

Answer 5

No. Varies from person to person.

Question 6

How can STR (short tandem repeats) sequences be separated?

Answer 6

electrophoresis

Question 7

Each STR is polymorphic, what does this mean

Answer 7

having more than one form – may refer to variations within the DNA sequences of a particular gene. (alleles)

Question 8

What are the advantages of the technique used to analyse STRs

Answer 8

• very sensitive, and even trace DNA left when someone touches an object can produce a result
• DNA samples can be stored for many years if a crime case is unsolved

Question 9

What are the disadvantages of the technique used to analyse STRs

Answer 9

samples have to be treated carefully to avoid contamination

Question 10

Applications of DNA profiling in regards to forensic science

Answer 10

• conviction of crimes
• Proving innocence
• Used in immigration cases to prove or disprove family relationships
• paternity testing

Question 11

Applications of DNA profiling in regards to maternity and paternity disputes

Answer 11

• half of a child’s STRs are from the mum, half from dad so comparing DNA profiles of mother, father and child can establish maternity/paternity

Question 12

Applications of DNA profiling in regards to analysis of disease

Answer 12

• protein electrophoresis can detect type of Hb present and help in diagnosis of sickle cell anaemia
• varying no. of repeat sequences for conditions like Huntington disease can be detected by electrophoresis