03 - Chick Check: The Genetics Behind Blue Chicken Eggs
Introduction Students will uncover the genetics behind how some chickens lay blue eggs and how this genetic trait is inherited. They will compare DNA from different chicken breeds that lay blue or non blue shelled eggs, use a 3-primer PCR test to detect a viral DNA insertion near the SLCO1B3 gene that causes the blue shell phenotype, analyze DNA band patterns on an agarose gel, and use the results to choose breeding pairs that will produce a line of chickens that reliably lays blue eggs (homozygous blue). Background Information The Science Behind Blue Eggs: Why So Blue? Chicken eggs are most commonly white or brown, but some chicken breeds lay eggs with blue or even green shells. The blue shell color comes from a special blue/green biological pigment called biliverdin that gets deposited into the eggshell of certain chickens during formation in the hen’s shell gland or “uterus” (Figure 1).
Vent
Vagina
Ovary
Uterus or shell gland
Cloaca
Infundibulum
Magnum
Isthmus
Figure 1: Chicken reproductive tract.
What is biliverdin? You might recognize the name bilirubin as it is the compound that makes newborn babies look yellow when they have jaundice. Well, biliverdin is bilirubin’s “chemical parent,” and both are breakdown products of red blood cells. But while bilirubin appears yellow-orange, biliverdin has a beautiful blue-green color. In fact, biliverdin is what gives some sea creatures like horseshoe crabs and certain marine worms their striking blue blood! Chickens primarily express blue/green biliverdin in their liver and bile because they have low levels of biliverdin reductase, which is an enzyme that normally converts blue/green biliverdin to orange/yellow bilirubin in the liver of mammals. Chickens contain a special gene called SLCO1B3 that codes for the protein OATP1B3 which is re- sponsible for transporting bile acids and biliverdin from the blood into the liver for further breakdown and processing.
28
Visit our website at www.edvotek.com
Made with FlippingBook flipbook maker