DNA Analysis and Interpretation

Question 1

What is fluorescence used for?

Answer 1

• Both saliva and semen fluoresce by using UV light
• Rely on detected the enzyme acid phosphatase on stained clothing
• AP is a common enzyme so you can often get false positives

Question 2

Blood samples

Answer 2

• Required to be preserved in EDTA if DNA is required
• Need samples that require nucleolus - red blood cells and platelets
• White blood cells and leucocytes dont have nucleolus
• Blood consists of 45% red blood cells and 1% white blood cells

Question 3

Semen analysis

Answer 3

• Some people will fail to ejaculate or may suffer from conditions where they lack spermatozoa
• Use two-step differential extraction of sperm and vaginal epithelial DNA

Question 4

DNA-17

Answer 4

• Looks at 17 STR loci sites
• More discriminatory power compared to the old technique
• Much better with smaller degraded samples

Question 5

Faeces

Answer 5

• Epithelial cells in faeces is what we use to recover DNA

Question 6

Presumptive testing

Answer 6

• If possitive is a presumption - would need to do further testing
• If negative is a rejection - analysis would cease at this point
• Used to test for blood, saliva or semen

Question 7

What is the luminol presumptive test?

Answer 7

• Presumptive test for blood
• Positive test by the emission of light

Question 8

What is the KM presumptive test?

Answer 8

• Presumptive test for blood
• Positive result from pink colouration
  1. Use circular filter paper and rub on ‘blood’ stain
  2. Add ethanol
  3. Add Kastle Meyer solution
  4. Add hydrogen peroxide

Question 9

What is the LMG presumptive test?

Answer 9

• Presumptive test for blood
• Blue-green colour change for a positive reaction
  1. Use circular filter paper and rub on ‘blood’ stain
  2. Add ethanol
  3. Add LMG solution
  4. Add hydrogen peroxide

Question 10

What is a confirmatory test for blood?

Answer 10

Old: The precipitin test
* Used to identify if it is human or animal DNA
1. Animal is injected with human blood
2. Animal makes anti-human antibodies
3. Animal blood is extracted
4. The extracted animal blood is used to test other blood to identify whether the blood is of human origin
New: go straight to DNA

Question 11

What is the ELISA Test?

Answer 11

• Presumptive test for saliva

Question 12

What is the phadebas test?

Answer 12

• Presumptive test for saliva
• Will fluoresce blue if saliva is present
• Helpful when salvia isnt visible

Question 13

Describe the process of DNA replication?

Answer 13

• DNA replication is the process by which a cell makes an indentical copy of its DNA
• It invloves the unwinding of the DNA double helix, the synthesis of new complementary strands by DNA polymerase, and the proofreading and repair of any errors

Question 14

What is the role of DNA polymerase in DNA replication?

Answer 14

• DNA polymerase is the enzyme responsible for synthesizing new DNA strands during replication
• It adds nucleotides to the growing DNA chain in a complementary fashion, using the existing DNA strand as a template

Question 15

What is a DNA profile

Answer 15

• A DNA profile is a distinctive pattern of a persons STRs that have been separated by electrophoresis
• Look at the same bands in the same location when matching suspect to a crime scene
• A person gets their DNA from their parents - half from mother and half from father

Question 16

What is an electropherogram?

Answer 16

• Graph produced when electrophoresis is used
• In a complete profile, each person will exhibit either one or two peaks (alleles) at each gene locus
• Loci that display only one allele indicate the individual inherited the same marker from both parents (peak is usually taller)

Question 17

Hierarchy of Propositions

Answer 17

1. Offence - guilt or innocent
2. Activity - an activity
3. Source - source of the biological material
4. Sub-source - source of the DNA
5. Sub-sub-source - source of a specified component of the DNA profile

Question 18

Partial copies of DNA, shorter & containing only one side of the ladder?

Answer 18

RNA

Question 19

Proteins which read the RNA code, three letters at a time?

Answer 19

Ribosomes

Question 20

DNA precipitate is washed with alcohol in this step

Answer 20

Purification

Question 21

EPG meaning

Answer 21

Elctropherogram

Question 22

The peaks on the EPG respresent potitions on the?

Answer 22

Chromosome

Question 23

In cryogenic recovery of DNA, after retrieval of bone sample the next step is?

Answer 23

pulverisation

Question 24

After pulverisation, the powder is then subjected to remove the calcium in the process of?

Answer 24

decalcification

Question 25

The liquid portion of the centrifuged sample?

Answer 25

supernatant

Question 26

DNA is synthesised continuously in this direction?

Answer 26

5-3

Question 27

Increasing the number of genetic markers provides more?

Answer 27

discrimination

Question 28

DNA evidence can produce evidence which is?

Answer 28

• exculpatory

Question 29

What joins fragments in the lagging strand?

Answer 29

DNA ligase

Question 30

What enzyme synthesises RNA primers?

Answer 30

RNA primase

Question 31

In DNA replication the strand which synthesises continouously in 3 to 5 directin is?

Answer 31

leading strand

Question 32

Lagging strand synthesised in short fragments called?

Answer 32

Okazaki fragments

Question 33

What glands secrete substances by the way of a duct?

Answer 33

exocrine

Question 34

What are red blood cells called?

Answer 34

erythrocytes

Question 35

What test is used nowadays to locate saliva deposits and replaced the ELIZA test?

Answer 35

phadebas