DNA Fingerprinting

Question 0

Name three steps in preparing a DNA fingerprint

Answer 0

1) obtaining samples
2) extracting and quantifying the DNA
3) analysing the DNA

Question 1

Forensic science

Answer 1

The intersection of law and science. Using scientific tests in the investigation of crimes.

Question 2

VTNRs (variable number tandem repeats)

Answer 2

Repeated sequences of between 1 and 100 base pairs located in the the introns

Question 3

Ideally DNA loci analysed should:

Answer 3

1) be highly polymorphic
2) be easy and cheap to characterise
3) give profiles that are simple to interpret
4) have a low mutational rate

Question 4

DNA databases

Answer 4

A collection of DNA profiles from evidence found at unsolved crime scenes and from suspects and convicted criminals

Question 5

DNA fingerprinting

Answer 5

A technique used to link biological samples from a crime scene to a suspect

Question 6

Why would you collect DNA profiles in a database?

Answer 6

1) criminals tend to reoffend
2) the severity of crimes often increases
3) a small number of people are responsible for a large number of crimes

Question 7

Reasons why some people consider DNA databases an invasion of privacy

Answer 7

• people are worried that insurance companies or potential employers will use them to identify genetic defects that might cost them money
• concerned with illegitimacy

Question 8

Restriction endonucleases

Answer 8

Bacterial enzymes that cut at a specific DNA sequence

Question 9

RFLPs

Answer 9

Variations among individuals which prevent restriction enzymes from cutting at specific base pairs

Question 10

Locus

Answer 10

Target area on DNA fragment

Question 11

2 main aims of DNA extraction

Answer 11

Maximise yield and maximise purity of DNA

Question 12

Factors that determine method of DNA extraction

Answer 12

• type of biological sample
• speed
• automation
• cost

Question 13

4 extraction methods commonly used in forensics labs

Answer 13

1) Chelex 100 resin
2) Silica-based extraction
3) Phenol-chloroform extraction
4) FTA paper

Question 14

Principle by which Chelex 100 resin works

Answer 14

Resin has a high attraction for polyvalent ions (Mg2+). It will isolate the proteins at the bottom of the tube

Question 15

Principle by which silica-based DNA extraction works

Answer 15

DNA bunds to silica or glass particles in 6MNaCl

Question 16

Principle by which the phenol-chloroform method of DNA extraction works

Answer 16

Phenol denatures the proteins that, after centrifugation ions are found at the interface while DNA remains in the aqueous phase

Question 17

Principle by which the FTA paper method of DNA extraction works

Answer 17

Cellular materials lysis on contact with the paper, DNA binds to the paper

Question 18

What are the nucleated cells in bone matrix called?

Answer 18

Osteocytes

Question 19

What are the nucleated cells in teeth called?

Answer 19

Odontoblasts and fibroblasts

Question 20

5 standards used for DNA fingerprinting

Answer 20

1) relevancy test
2) the Frye standard
3) the Coppolino standard
4) the Marx standard
5) the Daubert standard

Question 21

Relevancy test

Answer 21

Must be relevant to case

Question 22

Frye standard

Answer 22

Technique used to gather evidence must be generally accepted by the scientific community

Question 23

Coppolino standard

Answer 23

Allows a new/controversial technique if adequate foundation can be laid

Question 24

Marx standard

Answer 24

Court must be able to understand and evaluate the evidence presented

Question 25

Daubert standard

Answer 25

Requires pre-trial hearings for scientific evidence

Question 26

Chain of custody

Answer 26

A list of all people who came into possession of an item of evidence