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December 23, 2015

You read it HERE first. Two male red kangaroos at the Saint Louis Zoo are the suspects. One is the father of female 'roo Roothie born at the Zoo on April 8, 2013. But which one?

Knowing which male is the father avoids any problems with Roothie mating with her dad and causing the population to lose genetic diversity. Zoos care deeply about genetic diversity, because it is directly related to species' fitness, which is measured by how many surviving offspring are produced.

Okay, so we'll fess up—it really has nothing to do with child support. But determining the dad of a red kangaroo does rely a bit on modern-day paternity testing techniques for humans. That test compares a baby's DNA profile to that of the potential fathers and to the mother. Scientists look for the presence of particular genotypic markers when attempting to establish who fathered the child.

Markers also figure heavily in the forensic lab work the Saint Louis Zoo recently commissioned for red kangaroos. The Zoo turned to the Population Genetics and Disease Ecology Laboratory at the University of Missouri-St. Louis (UMSL) to take on the onerous task of determining which of two male kangaroos—Sebastian or Roopert—is the dad of Roothie. That lab is directed by Dr. Patricia Parker who is also Senior Scientist at the Zoo and the director of the Zoo's WildCare Institute Center for Avian Health in the Galápagos Islands. Dr. Parker is also the E. Desmond Lee Endowed Professor in Zoological Studies at UMSL. She asked her UMSL Laboratory Manager Cindee Rettke to spearhead the project.

"Kangaroo paternity was new to us, so we had to search the literature to determine whether there were genetic markers to use for the testing," said Cindee, who has managed the lab for nine years after working in the field of cancer research. "This is much like forensic lab work."

Dr. Parker and Cindee found a scientific article describing the work of researchers who had developed genetic markers for a kangaroo species. Thinking these markers could help determine the father of Roothie, Cindee purchased them to use for this project.

The next step was analyzing small blood samples that were taken from all the four animals during routine medical procedures. Cindee did an extraction to pull out the DNA from the blood. She then had to make sure the markers would work on the samples from the Zoo. She used the lab's polymerase chain reaction (PCR) machine. This technology is used to amplify a single copy or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. The PCR results allowed her to determine what markers she would use for the rest of the analysis.

Her next step was ordering a fluorescent dye from a specialty firm, so she can do fragment analysis to find the key genetic traits. This involves running more PCR reactions with the fluorescent markers and then running them through sophisticated equipment to produce fragments that are then separated by electrophoresis—a technique used in laboratories to separate macromolecules.

If it sounds complex, it is. But Cindee expects this complex equipment to spit out results that tell her whether Sebastian or Roopert fathered Roothie—all to avoid Roothie breeding with the wrong guy.

Watch for a future post telling you which kangaroo can claim lovely Roothie as his own daughter.

Photos featured here are of joeys born in 2015; not Roothie. Photos by JoEllen Toler.