Extinction of Chromosomes due to Specialization is a Universal Occurrence

The human X and Y chromosomes evolved from a pair of autosomes approximately 180 million years ago. Despite their shared evolutionary origin, extensive genetic decay has resulted in the human Y chromosome losing 97% of its ancestral genes while gene content and order remain highly conserved on the X chromosome. Five ‘stratification' events, most likely inversions, reduced the Y chromosome's ability to recombine with the X chromosome across the majority of its length and subjected its genes to the erosive forces associated with reduced recombination. The remaining functional genes are ubiquitously expressed, functionally coherent, dosage-sensitive genes, or have evolved male-specific functionality. It is unknown, however, whether functional specialization is a degenerative phenomenon unique to sex chromosomes, or if it conveys a potential selective advantage aside from sexual antagonism. We examined the evolution of mammalian orthologs to determine if the selective forces that led to the degeneration of the Y chromosome are unique in the genome. The results of our study suggest these forces are not exclusive to the Y chromosome, and chromosomal degeneration may have occurred throughout our evolutionary history. The reduction of recombination could additionally result in rapid fixation through isolation of specialized functions resulting in a cost-benefit relationship during times of intense selective pressure.

Name thesis:degree_name

M.S. (Master of Science)

Level thesis:degree_level

M.S.

Discipline thesis:degree_discipline

Bioinformatics (UMKC)

Grantor

University of Missouri--Kansas City

Year dc:date.issued

2019

Author dc:creator

• Wilson, Jason Ryon

Advisor dc:contributor.advisor

• Wyckoff, Gerald J.

Handle dc:identifier.uri

https://hdl.handle.net/10355/70902

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/70902