Benefits of New Multiplexes Flashcards
What is a multiplex?
Combinations of loci
What is SGM?
- Second Generation Multiplex
- comprised of six loci plus a genetic identifier
What is SGM+?
- number of loci increased to 10
- included all the loci from SGM so that it was back-compatible with previous SGM multiplex
What is the order of all the multiplexes in earliest to latest?
- RFLP
- MLP
- SLP
- STR-Quad
- SGM
- SGM+
- DNA17
What are the three types of DNA match?
- between a reference sample and undetected crimes (person to crime)
- crime to crime
- person to person
The multiplex, used the formation of the DNA database, in 1995 was referred to as?
SGM
Why is DNA 17 needed?
- adventitious matches
- can analyse degraded DNA
Prior to DNA17 we all used SGM so what does this mean for samples?
if a crime stain is profiled using one multiplex, and a reference sample uses a different one they may not quite match for several reasons
What is near match reporting?
It is used to identify individuals who may not have an exact match to the DNA profile from the crime scene evidence but share significant similarities
What are reasons for non-concordance?
- data entry error
- two profiles are very similar
- mutation
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
How does mutation cause non-concordance?
- crime scene sample might be profiled using one multiplex while the reference sample is profiled with a different multiplex
- to combat this we can retest the crime stain and reference sample using the same multiplex
What is the Prum Convention 2005?
enables the routine exchange of data of DNA profiles and fingerprints
How does compatibility work with the Prum Convention 2005?
- there are many multiplexes that different countries use
- the loci used can vary between these tests
- it is necessary to find out which loci were shared and therefore they can be compared in cross-border searches
What is the ESS?
European Standard Set
* sets of seven loci were specified as the basic set for comparision
* these seven loci are included in all multiplexes
* at least 6/7 of the ESS loci are needed before a search can be carried out
What are the two reasons that DNA can become damaged?
- breaking down or degraded
- presence of chemicals in the sample which inhibited the DNA reaction
What were the ENFSI requirements for an imrpoved DNA test?
- include more loci
- be more robust to inhibition
- get better results from smaller and more degraded samples
How is continuity and back compatibility ensured between the old SGM multiplex and DNA17?
- the original six SGM loci were included in the SGM+ test
- the SGM+ loci are included in the DNA 17 tests
What is the interpretational issue due to new tests?
- rather than having a single test like SGM+, several companies have produced their own versions of multiplexes
- these meet or exceed the ESS criteria
- the order and position of the loci are not the same between the multiplexes
What is benefical about the number of PCR cycles being increased?
- more sensitive
- able to give better profiles from small and degraded samples
What are the benefits of the new multiplexes?
- more sensitive
- can analyse more degraded smaller samples
- fewer problems with the chemicals that inhibit samples
- increased cycle number of PCR
The presence of chemicals in the DNA crime sample can influence the quality of the resulting DNA profile. In this instance, the sample is said to be?
inhibited
The current DNA multiplex requires how many cells to commence the standard test?
80
