dna profilling

Question 1

a genetic fingerprint is not the same as a dna sequence because

Answer 1

represents only non coding regions

Question 2

what are within introns

Answer 2

short sequences of dna which repeat many times
short tandem repeats strs

Question 3

producing dna profile

Answer 3

• dna from sample cut into fragments using restriction endonucleases
• fragments must be separated using gel electrophoresis
• gel is made from agarose (containing pores)
• dna fragments added to wells and voltage applied
• dna attracted to positive as dna itself is negative
• smaller fragments travel further through pores in the gel as they are lighter
• alkaline solution added to seperate double strands of dna
• gene probe added which is either a radioactive tracer or flourescent label
• binds to complementary nucleotides (dna hybridisation)
• southern blotting- agarose gels are really fragile so this process transfers dna using nylon filter onto much tougher membrane
• dna fragment which contains sequence of interest is identified by its fluorescence or radioactive signal

Question 4

gene probe

Answer 4

short dna sequences which are complimentary to specific sequences which are being sought

Question 5

PCR
polymerase chain reaction

Answer 5

amplifies dna (makes copies)
large number of copies of specific fragments of dna may be made rapidly
- during reaction thermocycler used to rapidly change temp
- heat to 95degrees to separate dna strands by breaking hydrogen bonds between two complimentary dna strands
- cool to 50-60 to allow primers to attach by CBP
- heat to 70 to allow dna polymerase to join complimentary nucleotides

Question 6

limitations of PCR

Answer 6

• any contamination is quickly amplified
• dna polymerase can sometimes incorporate incorrect nucleotide
• only small fragments can be copied

Question 7

primer

Answer 7

short single strand of dna that is complimentary to the base sequence at one end of a single stranded dna template, acting as a start point for dna polymerase to attach