1. DNA FINGERPRINTING Gel Electrophoresis

2. DNA Fingerprinting
To compare DNA from one organism with DNA of other organisms
(for paternity, crime-solving):
Step 1
Cut DNA into fragments
Step 2
Separate the fragments
Step 3
Compare the fragments

3. DNA Fingerprinting
To compare DNA from one organism with DNA of other organisms
(for paternity, crime-solving):
Step 1
Cut DNA into fragments – restriction enzymes
Step 2
Separate the fragments –
gel electrophoresis

4. RESTRICTION ENZYME CLEAVES DNA
Step 1
Small pieces of DNA must be cut from a larger chromosome
RESTRICTION ENZYMES = bacterial proteins that have the ability to cut both strands of the DNA molecule at a specific nucleotide sequence

5. Gel Electrophoresis

6. Step 2 Separate the small pieces of DNA – fragments – using gel electrophoresis

7. Sample of DNA put into well at one end of the gel

8. Gel Electrophoresis
Current applied
DNA separated into fragments – why?
DNA is negatively charged
Size: smaller fragments can go farther
Result: individual “DNA Fingerprint”
NOT a print of a finger, but DNA fragments

9. Gel Electrophoresis

10. Gel Electrophoresis

11. DNA Fingerprint Uses non-coding DNA sequences – “Junk” DNA WHY?
Within coding DNA (3%) –little variation
Within noncoding DNA (97%) – much more variation
Individuals, even though they possess many common genes, differ widely in their noncoding DNA
More related  more similarity of DNA

12. Step 3 Compare the fragments Recall that half of an organism’s DNA comes from the Mom, half comes from the Dad

13. Who are the soldier’s parents?
Problem-Solving Lab on page 353
Who are the soldier’s parents?

14. Examine each fragment of the soldier, one at a time
Top fragment: had to come from Mom or Dad
Where did it come from?
Not A or B, but other parents are possible
Rule out parents A&B

15. Next fragment
Came from C, E, or H
Came from C or F
Rule out parents G & H
Had to come from Parent C

16. Blood on defendant’s clothes – is it defendant’s blood or victim’s blood?

17. What does a restriction enzyme do to a DNA molecule?
Quick Review
What does a restriction enzyme do to a DNA molecule?
Answer
It cleaves (CUTS) or opens a DNA molecule at a recognition site leaving a space for another piece of DNA to fit in. The open ends are called sticky ends.

18. CLASSWORK Worksheets: Complete the two DNA fingerprint analyses
Then create a similar gel and story
Where are the wells?
Which end is + and -?
Each child’s DNA fragment must come from either his father or mother
Answer all items on the worksheet