On any given day, I never know what species I will be working with in the Genetics Laboratory of the San Diego Zoo Institute for Conservation Research. Today it was a western lowland gorilla (48 chromosomes), an eastern red kangaroo (20 chromosomes), and a hooded pitta (too many micro-chromosomes to count, but we can confirm the species and gender).
In 2011, we added 23 new species to our Frozen Zoo® fibroblast cell line collection: 13 birds, 4 reptiles, 5 mammals, and 1 amphibian. This is amazing, as we already have about 900 species/subspecies represented in the Frozen Zoo, so therefore it is difficult to get samples from species we do not already have represented. We also looked at the chromosomes and did karyotype case studies on 270 different individual animals this past year.
We start with a small skin biopsy (about the size of a pea), and from that we are usually able to establish a cell line. These cells are then frozen in liquid nitrogen (-321 degrees Fahrenheit or -196 degrees Celsius) and placed into boxes and racks that go into the freezers that are the Frozen Zoo. Every cell line in the Frozen Zoo is then checked for quality control by thawing one vial of cells. We see how well the cells recover from freezing and also harvest the cells in metaphase and look at the chromosomes.
Karyotyping is the best part of my day. It’s like doing a jigsaw or crossword puzzle: you never know how it’s going to work out or what your picture will look like, but when you finish the puzzle, it is really great! Chromosomes are lined up by shape and size, and then their karyotype, or genetic map, is compared to published karyotypes or ones that we have done previously on the same species. We can see any chromosomal abnormalities, and we can confirm the gender and species of the animal.
By the way, the hooded pitta was a female, and the eastern red kangaroo had an inversion in pair two.
Suellen Charter is a research coordinator for the San Diego Zoo Institute for Conservation Research.