During our trip up to the old research labs at the San Diego Zoo, I tried to explain to the Girls In Science participants what exactly we would be seeing this week. The topic was fairly advanced science, and of all the things we’ve experienced this year, THIS was the area I was most concerned about. Would they be able to fully grasp the details of genetics and heredity? Would they care about sperm motility or ovum cryopreservation? Would they giggle through the entire lesson? Or would they settle in and take advantage of the information that was offered?

My fears were completely unfounded. I learned that, conveniently, the seventh graders in the group had just finished a block covering genetics and heredity! They were in their element and understood everything our cytogenetics presenter, Suellen Charter, had to say! Suellen showed us three different karyotypes, which are photomicrographs of chromosomes arranged according to a standard classification. Real photos of real chromosomes! The girls could count them (southern white rhinos have 82, tigers have 38, and Parma wallabies have only 16) and were able to identify the X and Y sex chromosomes. One of the cool things about the tiger karyotype we looked at was that it had 39 chromosomes!! How is that possible? Well, this particular tiger, Nick, had a condition called Kleinfelder’s Syndrome, which meant he carried two X chromosomes and one Y! This opened up a fascinating discussion about why he was in fact a male, and not a female, even though he carried two X chromosomes. I was amazed how interested the girls were! (The reason, incidentally, is that one Y supercedes any number of X chromosomes to dictate gender.)

We also visited a branch of the CRES Reproductive Physiology lab that is still located at the Zoo. We were lucky to be able to meet with Dr. Barbara Durrant, the division head, and lab techs Nicole Ravida and Dianne Amodeo to learn some of the finer details of what it is that they do! The girls were able to see sperm that had been previously frozen swimming under a microscope, and discovered that, if you look verrrry carefully, you can see a dog ovum with the naked eye. The samples we looked at came from domestic dogs that had been neutered and spayed in local clinics. Rather than tossing the tissue out, the vets saved it for our lab to work with, which is much easier than using cells from animals here at the Zoo. Once freezing techniques have been worked out using the domestic dog cells, then those techniques can be used with great assurance on cells of endangered species.

We also learned about hormone tests that are run on the female sun bears to find out when they are cycling and how cells can be stained to see if they survived the freezing process. As we made our way back down the steps and out of the building, one girl turned to me and admitted, “Wow. My head is spinning, but that stuff is amazing. I’m glad we got to come here.”

Me, too.

Thanks to the entire team for an enlightening afternoon!

Cindy Spiva-Evans is an educator at the San Diego Zoo.

Girls In Science is a program for Roosevelt Middle School girls which creates science-based experiences with professional women at the San Diego Zoo. The program is funded through the generosity of the Wells Fargo Foundation.

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