When cells undergo mitosis, they must replicate all six billion base pairs of DNA within the nucleus. With the sheer volume of information, it is impossible to replicate with 100% accuracy each time. Homologous recombination (HR) is one of many mechanisms the body has developed to correct and repair replication errors to DNA. HR is specific to double-stranded breaks to DNA, and it requires a sister chromatid to preserve the genetic code. BRCA1 and Rbbp8 interact to form a complex that is heavily involved in this process. Although there is a strong consensus about the involvement of these proteins in a cell cycle-dependent manner, there are discrepancies in the current literature regarding when homologous recombination repair occurs. The goal of this thesis is to elucidatethe true activity of BRCA1-Rbbp8 complex in the HR process. First, a meta-analysis was performed to review current research to understand the various experimental protocols that led to the conflicting conclusions about cell-cycle activity of HR. Then, we measured the mRNA levels of BRCA1 and Rbbp8 during different phases of the cell cycle.In order to accomplish this, the cell cycle of the L cells was synchronized using thymidine and RO-3306 for the S and G2phases, respectively. The RNA was collected and converted to cDNA via reverse transcriptase. Next, RT-qPCR was performed to measure the expression of BRCA1 and Rbbp8. The levels of Rbbp8 are not significantly different between these phases, though there was a clear downward trend worth noting. Furthermore, a statistically significant increase in BRCA1 as the cells moved from S phase to G2phase was observed. When normalized tothe housekeeping gene, GAPDH, the levels of mRNA for BRCA1 during the S phase were significant lower than the control group. These results suggest that HR occurs during both S and G2, but BRCA1 and Rbbp8 interact only during G2.

Thesis Completion




Thesis Chair

Hawthorne, Alicia


Bachelor of Science (B.S.)


College of Medicine


Burnett School of Biomedical Sciences



Access Status

Open Access

Release Date


Restricted to the UCF community until 5-1-2019; it will then be open access.