Poster abstracts
Poster number 54 submitted by Brittany Hamilton
Stability of circularized chromosomes lacking telomeres in Saccharomyces cerevisiae
Brittany M. Hamilton (Rowan County Senior High School), Melissa A. Mefford (Department of Chemistry and Biology, Morehead State University)
Abstract:
Chromosomes carry the genetic information of an organism. Prokaryotic cells generally have a single circular chromosome, whereas eukaryotic cells have multiple linear chromosomes. Telomeres, repetitive DNA sequences at the ends of linear chromosomes, serve as protective caps to avoid loss of important genes during cell division; with each round of division, telomeres shorten and thus impose a limit on the number of divisions a cell can undergo. This is known as the end-replication problem. To get around this issue, telomeres utilize telomerase, a ribonucleoprotein enzyme complex that adds repeat sequences to telomeres maintain length. To understand how and why eukaryotes evolved to have linear chromosomes, despite their seeming disadvantages, we have genetically engineered the linear chromosomes of the budding yeast Saccharomyces cerevisiae to create circularized versions. Our approach involves inserting unique DNA cassettes into subtelomeric regions of each chromosome arm, which allow for recombination between the two arms and thus circularization of the chromosome. Our lab has successfully circularized four of the sixteen yeast chromosomes (Ch. II, IV, VIII and XV). Interestingly, some chromosomes (Ch. I, III, VI) have been difficult to achieve integration and circularization using our approach, which we are interested in following up on. However, using our successfully circularized strains, I have begun investigating the stability of the circularized chromosomes over multiple generations using serial restreaking and monitoring for maintenance or loss of circular chromosomes in both haploid and diploid strains. Understanding the effects of circular chromosomes in eukaryotes and thus why linear chromosomes have evolved can open opportunities for novel investigation into two of the largest human health concerns, aging and cancer.
Keywords: telomere, telomerase, chromosome