MadSci Network: Genetics

Re: Would it be possible if my children have green, blue or light eyes?

Date: Wed Nov 26 18:45:02 2003
Posted By: Christopher Carlson, Senior Fellow, Dept. of Molecular Biotechnology
Area of science: Genetics
ID: 1066968916.Ge

Hi Angie,

  Eye color is not nearly as simple as you may have been led to believe, because 
there are truly infinite gradations across the spectrum from blue to green to grey to 
amber to brown.  However, for the sake of argument, let's assume that there are 
only two colors: dark and light.  Furthermore, let's assume that these two eye colors 
are the result of genotype at a single locus with two alleles: B (dark) and b (light), 
with B dominant over b.  Humans are diploid, receiving one copy of the genome 
from each parent, so individuals with genotype bb will have light eyes, and 
individuals with genotype Bb or BB will have dark eyes.

  You and your husband are both dark eyed, and therefore either Bb or BB 
genotype.  So, in this simple model, the probability that you and your husband (both 
dark eyed) would have a light eyed child is the product of the probability that you 
are both genotype Bb and the probability that the child inherits the b allele from 
both of you.  If we knew that you both were Bb, then the probability of a bb child 
would be 25%.   However, working out the probability that you and your husband 
are both Bb is considerably more complicated, and not really worth the effort given 
that we know our model is oversimplified to begin with.  Suffice it to say that the 
maximum probability of a light eyed child under this simple model is 25%, but we 
made a number of assumptions (how many genes are involved, what the 
dominance relationship between alleles is, etc.) and therefore this number is only 
academically accurate.

  From a more realistic prespective, the answer I'd have to give is that it is certainly 
possible that you and your husband could have a light eyed child, but it's more 
likely that the child's eyes will be in the same range of the spectrum as you and 
your husband.  I honestly can't give you a more accurate prediction, because 
scientists have only begun to scratch the surface of pigmentation genetics.  If you 
are interested in more detail, please read my previous posts on this topic in the 



Current Queue | Current Queue for Genetics | Genetics archives

Try the links in the MadSci Library for more information on Genetics.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2003. All rights reserved.