Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Animal, Dairy, and Veterinary Sciences

Committee Chair(s)

Irina A. Polejaeva


Irina A. Polejaeva


S. Clay Isom


Barbara S. Durrant


Zhongde Wang


Aaron J. Thomas


Abby D. Benninghoff


Greg J. Podgorski


A significant issue in rescuing endangered species from extinction is the lack of access to germ cells (eggs and sperm). However, eggs from domestic animals could be used for cloning. This process involves removing the genetic material (gDNA) from the egg and replacing it with gDNA from an animal that belongs to an endangered species. There are a few problems that can occur due to the egg and the replacement gDNA coming from two different species. Both species have unique mitochondrial DNA (mtDNA) – this is different from the gDNA that contains the majority of an animal’s genes. mtDNA exists outside of the nucleus, and an egg has about 100 times more mtDNA than a non-germ cell. In the cloned embryo, most mtDNA is from the egg species, while the gDNA is from another species. This mismatch can negatively affect energy levels in the developing egg. In these experiments, we used a cow egg and gDNA from a goat. In an attempt to overcome this obstacle, we tried removing some of the cow mtDNA and introducing more mtDNA from the goat. We thought at least one of these methods would help the egg to develop further than it otherwise would. A second issue involves a milestone that a developing embryo must reach and progress past: embryonic genome activation (EGA). At this timepoint, the embryo starts using the new gDNA for information instead of what was stored in it before the gDNA was replaced. In the two-species embryos produced in our experiments, EGA-related signals can easily get crossed, which can cause the embryo to stop developing at EGA. In order to improve developmental progression, we introduced a chemical that had been shown to help the goat gDNA become more like gDNA of an early stage developing embryo. We thought that using this chemical would help the goat gDNA to progress through EGA. Four embryos were able to develop past EGA, though their progression stopped shortly thereafter. This might be because the cattle EGA happens before the goat’s EGA would, causing a bigger problem that our attempted solutions were unable to solve.



Available for download on Tuesday, May 01, 2029