H.J. Ruiz – Avian101

The domestic Crested Duck is a duck breed descended from the Mallard. It has its appearance because it is heterozygous for a genetic mutation causing a deformity of the skull. As a result, when a pair of crested ducks breed, the young sort out in the usual 1-2-1 ratio:-

• 25% are homozygous for the normal allele of this gene and so have no crest and if bred together their offspring will never have a crest.
• 50% are heterozygous for this gene and hatch with a crest of varying sizes.
• 25% are homozygous for the crested allele of this gene and die from exposed brain without hatching, as it is lethal in homozygous form.

If a crested duck and a non-crested duck breed together, the resulting ducklings would be expected to be 50% crested and 50% non-crested.

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My wife and I took Tyler to a local park to visit ducks or any other avian we could find there. Among the groups of species we found the one I described above and you’ll see the accompanying photographs.

Click on the images to see enlargements

Text and photographs © H.J. Ruiz – Avian 101