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Question
In college I was taught 2 blue eyed people can only have blue eyed children. Recently I was shown an online article that states it IS possible for 2 blue eyed parents to have a brown eyed child.

My question is, what are the approximate odds? 1 in 100, 1 in a million? I ask because I've never seen this happen before in my own experience.

How about the odds have 2 blue eyed parents having 3 brown eyed children? (Someone online says their in-laws both have blue eyes but 3 kids all with brown eyes.) Personally I wonder if the father was someone else or they adopted their kids.

Any info on the possible odds, even an educated guess would be appreciated!

Thanks!

Answer
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Eric,

The genes for brown and blue eyes requires two genes: OCA2 and HERC2. A working HERC2 is needed to turn on OCA2 and OCA2 helps to actually get the pigment made- and hence brown eyes.  They need each other to make pigment.

If someone makes a lot of pigment in the front part of their eye, they have brown eyes.  And if they make none there, they have blue. Also, if someone has a broken HERC2 genes, they will have blue eyes no matter what OCA2 says.  This is because the working OCA2 can't be turned on so no pigment gets made.

Because the two genes depend on each other, it is possible for someone to actually be a carrier of a dominant trait like brown eyes.  And if two blue eyed parents are carriers, then they can still have a brown eyed child.  Referring to a link:
http://genetics.thetech.org/how-blue-eyed-parents-can-have-brown-eyed-children

Working out the different combination of eye colore in parents, it is possible for blue eyed parents to have brown eyed children.  

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Thanemozhi Natarajan

Expertise

Answers in Genetics, genomics, cytogenetics of syndromes, congenital anomalies, cancer, clinical genomics and interpretation of omics data.

Experience

More than 10 years. Doctoral research thesis on Congenital anomalies and cytogenetics, Recurrent reproductive failure and chromosomal abnormalities. Postdoctoral experience in Breast cancer research. Current: Clinical Genomics and Pharmacogenomics.

Organizations
Academic

Publications
Cancer Cell International, Cancer Epidemiology Biomarkers and Prevention, Breast cancer research and treatment, Indian Journal of Pediatrics, BMC Proceedings, Pharmacogenetics and Genomics, Human Molecular Genetics, Frontiers in Genetics, Cancer Biomarkers.

Education/Credentials
PhD Biomedical Genetics

Awards and Honors
University Grants Commission Award for pursuing PhD level research (India); Travel awards to attend conferences.

Past/Present Clients
Post doctoral experience Cancer research, molecular epidemiology Current: Clininical Genomics and Pharmacogenomics

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