Blue or brown?

Marisa has brown eyes. I have blue eyes. Miekie and Pieter both have blue eyes. As eye colour is determined by genes and brown eye genes are dominant over blue eye genes, it follows that Miekie and Pieter inherited blue eyes from both Marisa and me. This means that Marisa is a carrier of the blue eye gene but that its expression (the phenotype) is overridden by the brown eye gene which she is also a carrier of.

Genetic crossover, the process by which a single set of 23 chromosomes is created from the double set in a parent for passing on to a child, is random and not influenced by the parent's phenotype. So Miekie and Pieter both received Marisa's blue eye gene by chance. As I have blue eyes it means I have two copies of the blue eye gene and thus our children have all received one of those from me. This means that the probability of one of our children having blue eyes is 1/2 because 2/2 (me) x 1/2 (Marisa) = 1/2 (child).

So statistically in only 1 of every 8 (which is 1/2 cubed) families with three children, where the parents have the same eye colour gene combinations as Marisa and I do, will all three children have blue eyes (or will all three have brown eyes). The probability for Neil having blue eyes is, of course, still 1/2 because his genes are not influenced by the genes of the other children. Although it's still too early to say for sure, we're starting to think that his eyes are getting a bit darker. Time will tell if he'll break the trend...


Anyway, here are a few photos that I took over the weekend.

The ascent

At the summit

Marisa wearing her Valentine's Day present around her neck

Milkshakes and coffee for 80% of the family; the remaining 20% received some milk upon arrival back home