Evidence Analysis, Recovery and QA Flashcards
When may DNA samples be rejected?
If they are non-compliant
What does PPE protect?
Staff and exhibits
How are exhibits separated?
By time and space
What is paramount in a lab?
Cleanliness
How is packaging opened?
In a way that protects the seals as much as possible
How are details of an exhibit recored?
On a worksheet
What is the point of examination?
To identify points of interest
What can go wrong in a lab? (6)
Staff, equipment, tests, procedures, integrity and delivery
How often is a method tested for quality control?
Constantly
What about samples is argued in court?
Integrity
How many cells are required for a DNA profile?
At least 3
How are results interpreted?
Based on guidelines
What happens when something goes wrong?
Corrective action is taken
What ensures standards are met?
Accreditation
What is removed in DNA extraction?
Interfering proteins and enzymes
What are the two DNA extraction steps?
Breaking the matrix and lysing the cells
How is a DNA matrix broken? (2)
Mechanical (Mortar and pesel) or Chemical (Protein Kinase A)
What is the difference between organic extraction, silica kits and Chelex?
Organic extraction is more pure but takes longer than Chelex. Silica kits are in between.
What is the most widely used form of DNA extraction?
Organic
Why is Chelex advantageous for PCR?
Because it removes inhibitors
What is quality assurance?
The planned, systematic practise to provide confidence in a product
What is quality control?
The scrutiny of daily techniques
Why are audits conducted?
To make sure standards are met
What do positive and negative tests ensure?
Reagents are working properly
What is validations purpose?
To show that techniques are robust
What provides interpretation guidelines?
Standard Operating Procedures
What does too much DNA result in?
Overblown electropherograms
What does too little DNA result in?
A loss of alleles
How many PCR cycles does it take to have 1 billion copies of DNA?
32
How large is a PCR assay?
5-100uL
What does a negative control test for?
Contamination
Why is contamination an issue with PCR?
Due to how sensitive the method is, it can detect very small amounts of DNA.
