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Gene evolution is defined as the process by which living organisms change over time through changes in the genome. In gene evolution, organisms will typically gain, lose or experience change in their gene structure. This will in turn give rise to genetic variation and results in changes in the physical or biological traits and functions of the individual. Some gene evolution will be adaptive, whereas some will be detrimental. Gene evolution is based on natural selection and hence, the survival of the fittest. Therefore, gene evolution is important to ensure that organisms are able to survive in an environment that is experiencing constant change. Gene duplication promotes biological innovation as it is an important source for new genetic material (Rivera & Swanson, 2022).
This brings us to the investigation of hatching enzyme genes. Hatching enzyme genes are used as a model to study gene evolution, duplication, and sub-functionalization (Kawaguchi et al., 2013). Hatching enzymes function to allow the embryo to break down and escape the egg envelope and become a free-living organism. Hatching enzymes are part of a highly dynamic gene family and are highly variable among different species (Nagasawa et al., 2022). Gene families are defined as a group of genes of similar nucleotide or amino acid sequences that share a common ancestor. Having a common ancestor means that they have hatching enzymes that likely share similar functions. Gene families typically arise from gene or genome duplication events.
In my thesis project, we will be characterizing and exploring the evolution of hatching enzymes in fishes. We will be using the low choriolytic enzyme (lce) and high choriolytic enzyme (hce) genes from the medaka fish (Oryzias latipes) as a base to explore their evolutionary relationships with those from other species of fishes. By using the medaka lce and hce sequences, we are able to trace the evolutionary relationships of these genes between different species of fish because many fishes have similar DNA sequences for these hatching enzymes.
After identifying the DNA sequences of hatching enzymes of different fish species, we will use the results obtained to infer a phylogenetic tree. Phylogenic trees are diagrams that show the evolutionary relationships of a group of organisms or genes derived from the common ancestor. By inferring a phylogenic tree, biologists are able to have a more in depth understanding of the evolutionary relationships and functional divergences between species and their genes. In conclusion, our objective is to learn more about gene evolution, duplication and sub-functionalization by exploring the evolution of the fish hatching enzymes.
Tan Ee Shuen, Shannon, "Exploring the Evolution of Hatching Enzymes in Killifishes" (2023). Honors Theses. 3714.