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About Darren Raffety
Expertise
I can answer questions relating to molecular genetics, specifically the roles that genes play in both health and disease in mammalian cells. I am also able to answer with relation to experimental organisms (e.g. S. pombe and S. cerevisiae) that are widely used in the biochemistry of genetics. I am knowledgable in the history of genetics ranging from the start (widely accepted to be Mendel, although his work was ignored for many years after his death). I can't answer questions directly relating to an individuals disorder only to give a general overview of widely accepted and experimentally proven concepts and theories. It is also impossible to determine the characteristics of an unborn child based on the phenotypes of the parents.

Experience
4 years educational experience at 2 UK Universities

Organizations
Instituate of Biomedical Sciences University of Sussex

Education/Credentials
BSc (Hons) Biomedical Sciences (University of Brighton) MSc Genetic Manipulation and Molecular Cell Biology (University of Sussex)

You are here: Experts > Science > Genetics > Genetics > question please

Genetics - question please

Expert: Darren Raffety - 11/3/2009

Question
QUESTION: Hi, I have a quick question can DNA tests for paternity ever be wrong? Assuming no tampering,expert staff and no human error. Would mothers breastmilk sway the results possibly?

ANSWER: Hi Mark,

There are two situations to consider in paternity tests relating to accuracy. In a situation where the individual is not related in any manner to the child, there is practically no room for there to be a mistake. Where the individual is related to the child, there is about a 0.01% chance of there being a mistake.

Interestingly, there is actually very little room for human error!

I hope this answers your concerns,

Regards,

Darren

---------- FOLLOW-UP ----------

QUESTION: Thank you Darren. I have a situation were I was excluded from being the babys father but the mother absolutely guarantees me that its mine since she says there has been no one else so it's impossible that I'm not the father. Now, providing she is telling the truth, how can I be excluded from being the father when (according to her) I am the father. If I were to take another DNA test should the results then be the same? What about these mosaic twins I've heard about could it be possible that I have two sets of different dnas and that's why it's concluding that I am not the father? How common are mosaics? How would I know if that's my situation?

ANSWER: Its a difficult situation however, mosaic twins are not only extremely rare but will still have some of your DNA in which to determine whether or not your the father. In particular, it is always the father that determines the sex of the baby and therefore will have at least one chromosome from you. You could take the DNA test again and in which case discuss the possibilities with the doctor, s/he would be a lot more familiar with your particular case.

Additionally, if you had different DNA it would normally be highly noticeable from your physical features.

Please do see your practitioner and discuss these concerns as its more likely you'll come to a satisfactory conclusion.

Regards,

Darren

---------- FOLLOW-UP ----------

QUESTION: Thank you Darren. I've done alot of research on paternity tests and I'm beginning to come to the conclusion that the babys mother is just a really very good liar. But to give her the benefit of the doubt, we have another daughter together who is older if I were to take a dna test with her and it showed I was the father would it throw the whole mosaic thing out the window since if I tested positive for her I should then test positive for the other one?

Answer
I'm trying hard not to reach any conclusions on whom is telling the truth ect and I'm a little worried regarding giving you advice that may influence your choice of actions.
I think it is safe to say that the mosaic twin theory of yours just doesn't fit this situation. In general, mosaicism occurs with one or two chromosomes only, and there will always be your genetics present in any viable offspring.
A paternity test on your older daughter would of course tell you if you are her father, if you are not, it will, with 100% accuracy, be correct. If you are the father, its 99.9% accurate.
Please do consult a practitioner, I feel that is the only way you can come to a conclusion on this one. If you can, please keep me informed as well.

Regards,

Darren

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