Benefits of Modern DNA Multiplexes Flashcards
What do forensic DNA tests look at?
- multiplexes - combination of several areas (locus/loci) of DNA
When are alleles said to match?
- when their peaks fall at the same position on the EPG
What was the test to produce DNA profiles when the national DNA database was set up in 1995?
Why was this not favoured for that long?
- Second-Generation Multiplex (SGM)
- comprised of 6 loci and AMEL test (indicating sex)
- there was a case of mistaken identity in 1999
- a six loci match (1 in 37 million)
- additional loci would have excluded the individual
What was the test used to provide DNA profiles for the UK DNA database in 1999?
- Second-Generation Multiplex + (SGM+)
- number of loci increased to 10
- all of SGM loci plus AMEL so test was back-compatible with previous multiplexes
Give a timeline of 1985 to 2014
1985 - MLP
1990 - SLP
1994 - STR - Quad
1995 - SGM
1999 - SGM+
2014 - DNA17
What are the three types of DNA match?
1 - person to crime
- between reference sample and undetected crime
2 - crime to crime
- investigative link between two crimes (useful in undetected crimes)
3 - person to person
- between reference samples
- means duplicates been identified (different names but same person)
What was the new method to produce DNA profiles introduced in the UK in 2014?
What are the reasons as to why this was developed?
- DNA17
- requests from police and investigators for undetected DNA profiles to be searched against databases from other countries
- easy to travel between countries means can escape abroad
- to deal with cross-border and inter-country crime
What are the six search requests within Europe?
- related to terrorist incidents
- trafficking of people
- drugs smuggling
- people smugglers
- serious crimes
- identification of missing persons and mass disasters
When can non-concordance occur?
if a crime stain is profiled using one multiplex and a reference samples uses a different one so they might not match
What is a near match report system?
- it is used to identify individuals who may not have an exact match to the DNA profile from the crime scene but share significant similarities
- it lists one allele differences between profiles
- it can be extended to investigate two or three allele differences between reference samples if needed
What is concordance?
- the agreement or match between two DNA profiles obtained from the same individual or from related individuals
- analysts look for concordance to determine whether the profiles match sufficiently to conclude that they originate from the same source
What are three reasons for non-concordance?
How can one of these by overcome?
1 - data entry error (typing incorrect number)
2 - sometimes the profiles can be very similar
3 - mutation (crime stain is profiled using one multiplex and the reference is a different multiplex)
- overcome mutation by retesting crime stain and reference sample using other multiplex
What was the Prum convention 2005?
How was compatibility a problem between different multiplexes?
- many EU countries signed up enabling the routing exchange of DNA profiles and fingerprints
- loci used in multiplexes used in different countries can vary between tests
- so it is necessary to find out which were shared and could therefore be compared in cross-border searches
What is the ESS?
- European Standard Set of Loci
- 7 sets of loci (polymorphic) specified as basic set for comparison
- at least 6/7 of ESS loci are needed before search can be carried out
What did the Prum convention say about ESS?
- agreed that 7 loci (polymorphic) from ESS should be in all multiplexes
