In this section there is a number of frequently asked questions related to DNA typing. Some of these questions have been taken from the book, Errors, Systematic Errors & DNA. A more comprehensive list of questions can be obtained from the above- mentioned book.
Question 1
What is DNA?
Answer -The shortens abbreviation DNA stands for Deoxyribonucleic acid. This is nature’s chemical code of life.
Question 2
What is nuclear DNA?
Answer- This is DNA derived from the nucleus. The nucleus controls the cell activities.
Question 3
What is mitochondrial DNA (m-DNA)?
Answer-This is DNA derived from the mitochondria. The mitochondria are a tiny structure in the cell, which provides energy for the cell to function.
Question 4
Is DNA typing accurate and reliable?
Answer-When DNA is processed properly and interpreted correctly, this technique is reliable and accurate.
Question 5.
The most common response would be zero. DNA laboratories would not admit to their mistakes unless you have identified a potential error. A better response is to enquiry about false positive rate, followed by a supplementary question may relate to the method of collecting biological information and assurance processes.
Question 6.
My client has had a vasectomy two years previous before having a paternity DNA test. It is impossible for him to be the biological father?
Conflicting science results concerning DNA typing and vasectomy has happened on some occasions in court hearings. DNA testing companies will insist their results are accurate and the fault lies with the vasectomy. However, you will have the opportunity to ask for the DNA test results to be investigated again for errors or misinterpretation of the results or request that for the DNA test to be carried out again by a different accredited forensic DNA laboratory. Unless, the DNA test result shows some form of error then in the majority of cases DNA typing will hold favour over vasectomy medical procedure. The real test is, if this evidence can be used to successfully sue the organisation that conducted the vasectomy.
Question 7
What are the main uses of DNA typing?
Answer-The main uses of DNA typing is the forensic identification of individuals in criminal investigations, resolving paternity issues, settling immigration matters and identifying corpses from mass graves. There are many other uses of DNA typing.
Question 8
What is the difference between DNA profiling and DNA fingerprinting?
Answer-Both terms are commonly used to forensically identify an individual. However, there is a subtle difference. DNA fingerprinting is primarily concerned with the length of a DNA strand, whereas DNA profiling focuses on the relative positions of DNA sequences.
Question 9
Can DNA decompose in the environment?
Answer- DNA can survive in the environment for some time. That’s why ancient bones can be identified. However, DNA will decompose according to atmospheric conditions and extremely high temperatures.
Question 10
Does laboratory errors exist?
Answer- All laboratory procedures have errors, however there are protocols and procedures that need to be followed to reduce the likelihood and effects of these errors.
Question 11
I have a twin, what is the percentage of genes I have in common with my twin?
Answer-100% if you are an identical twin and 50% if you are a non-identical twin.
Question 12
If I am blood group O and my partner is blood group A, what is the possible blood group of my offspring?
Answer-Possible offspring blood group is O or A.
Question 13
What is meant by the term NDNAD?
Answer-The term refers to the National DNA Database. This is the storage of biological information on the national database. (See glossary for other abbreviations).
Whilst contamination may affect the DNA test results, the DNA testing company will defend their position and provide some reasons that the results are unaffected. This means more probing questions will need to be asked. A better question may be how can you prove the absence of contamination?
My client has an alibi at the time at the scene of the crime therefore he or she cannot be the suspect and hence the DNA is at fault. How is your result possible?
Although the suspect’s alibis may be important to the court hearing, the DNA is powerful evidence and thus there is a need to determine if there is any error to the result.
Given that my client DNA profile match probability is of the order of 1 in 3.5 million of occurring by chance, this may be interpreted that approximately 18 people of the UK population of 62 million would have the same DNA profile match. Is this true?
The suspect must be drawn at random for this conclusion to occur. The proximity of the other 18 people must also be taken into account to give some credence to the above statement.
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