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Sex Determination in Birds (in our case; egrets)

Dr. David Shealer at Loras College has completed the first round of sexing of our Great Egrets.  Some name changes are in order as 4 or our 5 NC birds are male!

Unlike mammals (where males (XY) are heterogametic and females (XX) are homogametic), among birds the males are the homogametic sex (ZZ) and the females are heterogametic (ZW). Using molecular biology techniques, Dr. Shealer was able to magnify egret DNA we collected in the field using PCR (Polymerase Chain Reaction) and then use a primer to select for the segments of DNA (introns) that correspond to the Z and W regions. The Z intron is 650 base pairs (eg A-T or G-C are examples of 1 base pair) and the W intron is 470 base pairs. The wells in the gel where the samples are placed are at the top of the photo below:

When an electric current is applied to the gel, the magnified DNA is pulled through the gel based on its charge and size.  Small fragments move farther because they encounter less resistance from the gel.  So the 470 bp band travels farther than the 650 bp band.  You will see that males have only one band in their lane (both Z's) and females have two bands (ZW). To make a long story short:  Here are the results:     Palma: Male,      Heller: Female,     Newbern: Male,        Bisbing: Male,       Kelly: Male