6.1.3 Producing A DNA Profile

Question 1

Step 1- extraction

Answer 1

Extraction of DNA from tissue sample

Question 2

Step 2- digestion

Answer 2

Fragments cut into satellites by restriction endonucleases; each type of endonuclease cuts a specific base sequence called the recognition site; both DNA strands

Question 3

Mini satellite?

Answer 3

Contain repeats of 20-50bp sequences

Question 4

Variable number tandem repeats?

Answer 4

VNTR; mini satellites

Question 5

Micro satellites?

Answer 5

Repeats of sequences 2-4bp long

Question 6

STR?

Answer 6

Short tandem repeat; micro satellites

Question 7

Restriction endonuclease?

Answer 7

Enzyme used to cut DNA

Question 8

Step 3- separation of fragments

Answer 8

Using electrophoresis; DNA has a slight positive charge so is able to move when electricity is passed through the gel

Question 9

Step 4- separation of fragments

Answer 9

Gel is immersed in alkali so strands break apart; strands transferred onto a membrane using southern blotting

Question 10

Step 5- hybridisation

Answer 10

Radioactive / fluorescent DNA probes are added to the membrane; they bind to DNA in specific temperature and pH conditions; attach to particular micro satellites

Question 11

DNA probes?

Answer 11

Short sequences of DNA that are complementary to specific sequences of DNA

Question 12

Step 6- development?

Answer 12

Radioactive probes- x-ray taken of blot; fluorescent probes- UV light used to look at blot; gives pattern of visible bars that are specific to the sample taken