IrisPlex for Detection of Eye Colours from DNA?

[jimmydasaint 176]

I have recently read about a method for detection of blue and brown colour in Europeans using DNA samples. Apparently the iris colour (eye colour) has different forms of the same gene called alleles. There seem to be a number of alleles for brown or blue iris colour which differ apparently by a single base on the DNA (called Single Nucleotide Polymorphism IIRC).

 

However the technique is not explained in the abstract well and I want to understand it better, Can someone with a better knowledge help me understand it?

 

A new era of 'DNA intelligence' is arriving in forensic biology, due to the impending ability to predict externally visible characteristics (EVCs) from biological material such as those found at crime scenes. EVC prediction from forensic samples, or from body parts, is expected to help concentrate police investigations towards finding unknown individuals, at times when conventional DNA profiling fails to provide informative leads. Here we present a robust and sensitive tool, termed IrisPlex, for the accurate prediction of blue and brown eye colour from DNA in future forensic applications. We used the six currently most eye colour-informative single nucleotide polymorphisms (SNPs) that previously revealed prevalence-adjusted prediction accuracies of over 90% for blue and brown eye colour in 6168 Dutch Europeans

 

http://www.ncbi.nlm.nih.gov/pubmed/20457092

Edited June 8, 2014 by jimmydasaint

[jimmydasaint 176]

OK, a bit of reading makes a little bit more sense. Back to the initial O.P. SNP's are single nucleotide polymorphisms, where different forms of the same gene for eye colour differ by one base.

 

For example, these can be thought of as SNP's

1. ...CTGAATGA...

2 ...CTGATTGA...

3 ...CTGACTGA...

4 ...CTGAGTGA...

 

 

These can be detected in Europeans so that blue, brown or any combination can be detected using two techniques.

This means that, at a crime scene, DNA can be extracted from body tissues and the eye colour can be predicted with a high degree of accuracy.

 

The first technique uses a short DNA primer which is a short piece of DNA complementary to the DNA sequence containing the SNP. The reaction mixture also contains DNA polymerase which is an enzyme that extends the DNA. It also contains nucleotides called dideoxynucletide phosphates which which stop the DNA polymerase after it adds the base complementary to the DNA sequence containing the SNP. These dideoxynucleotide phosphates contain a fluorescent compound which can be detected by a laser. Each dideoxynucleotide phosphate is attached to a different fluorescent marker.

 

 

Next, let's imagine that we use a short DNA primer containing the following sequence:

....GACTT

 

after binding to SNP No. 1, the DNA extension by the DNA polymerase is stopped and the fluorescent marker is identified by a laser when DNA's are separated by a technique called capillary electrophoresis which I do not understand.

http://learn.genetics.utah.edu/content/pharma/snips/

 

 

Any thoughts and corrections to what I have written are welcome.

Edited June 8, 2014 by jimmydasaint