1. Ch. 11: DNA Analysis

2. DNA: Deoxyribonucleic Acid
Nucleotide:
Sugar (deoxyribose)
Phosphate
Nitrogenous Base
4 different bases:
Adenine
Thymine
Cytosine
Guanine

3. DNA: Deoxyribonucleic Acid
Found in all nucleated body cells:
WBC, saliva, semen, urine, hair root, teeth, bone, soft tissue, etc.
RBC have no nuclei, therefore DNA in blood samples comes from WBC
Most abundant in buccal (cheek) cells

4. Restriction Enzymes Bacterial defense mechanism
Cut DNA molecules at specific sites (certain nucleotide sequences)
We will be using Hae III

5. Hae III cut site
. . . C C G G G G C C . . .

6. Gel Electrophoresis
Uses electric current to separate DNA fragments by size
Smaller DNA pieces migrate faster through gel

7. DNA Fingerprinting
Everyone’s DNA sequence is slightly different (0.1%, or 3 million base pairs)
Restriction enzymes cut different sized pieces (fragments)
RFLP = restriction fragment length polymorphism

8. Uses of DNA Profiling To identify potential suspects
To exonerate individuals
To identify crime and casualty victims
To establish paternity
To match organ donors

9. DNA Exoneration

10. DNA evidence makes up part of the case against the defendant

11. Polymerase Chain Reaction (PCR)
Uses DNA polymerase to amplify DNA (make a LOT of copies of a target sequence)
Valuable when amount of evidence is minimal
Millions of copies can be made from a single speck of blood

12. Short Tandem Repeats (STR)
STR’s are locations (loci) on the chromosome that contain short sequences of 2 to 5 bases that repeat themselves in the DNA molecule.
The advantages of this method are that it:
Offers greater specificity*
Requires less time
Requires smaller sample size
Is less susceptible to DNA degradation
*The number of possible individual STR profiles greatly exceeds the estimated number of humans who have ever lived, so it is nearly impossible for a random match to occur.

13. FBI’s CODIS DNA Database
Combined DNA Index System
Used for linking serial crimes and unsolved cases with repeat offenders
Launched October 1998
Links all 50 states
Requires 4+ RFLP markers and/or core STR markers

14. CODIS = Combined DNA
Index System

15. STR Genetic Profile Allelic Ladders
D3S1358
VWA
FGA
AMEL
D8S1179
D21S11
D18S51
D5S818
D13S317
D7S820

16. STR Example Profile

17. STR Interactive Animation
The website below has an informative STR animation demonstration.
Click on “human identification”, “profiling” and then on the third circle called “Today’s DNA Profiling” to see the demonstration.
Print & complete the STR WORKSHEET before your next NB check!

18. Mitochondrial DNA (mtDNA)
Found in cytoplasm of cells
Inherited only from the mother (egg cell)
mtDNA is constructed in a circular or loop
As opposed to nuclear DNA, analysis of mtDNA is more:
rigorous
time consuming
Costly
Is used when nuclear DNA typing is not possible (i.e. skeletal remains)