Counting chromosomes: Exploring evolutionary insights from Drosophila karyotypes

Monday, November 11, 2024

10:54 AM – 11:06 AM MST

Location: Phoenix Convention Center, 223, PCC

Presenting Author(s)

Audrey Elizabeth French (she/her/hers)

Undergraduate Student
Utah Valley University
Pleasant Grove, Utah

Chromosome number is one of the first pieces of information collected about an organism’s genome. These numbers have been shown to vary widely across animals, with the smallest number in an ant (1n = 1) and large numbers in a lepidopteran species (1n = 224). As the Drosophila species group has been a model for more than 100 years, there is an abundance of information on their karyotypes, including number, chromosome shapes, and sex chromosome systems (XY, neo-sex, and X0). The numerous species of Drosophila can be compiled into the major subgenera of Drosophila and Sophophora, which have diverged for around 40-65 million years. Recently, karyotype data of the Drosophila genus has been compiled into an open-source database, which I am using for this study. I estimate the rates of chromosome number change within the genus Drosophila and between the subgenera Drosophila and Sophophora. I also investigate the differences in rates of change between sex chromosome systems. To perform the analysis of chromosome number change, I use comparative phylogenetic analyses through the chromePlus package in R (Blackmon et al., 2019) with a previously published phylogeny of the Drosophila genus. Using these available tools, I compare rates of fusion and fission between sex chromosome systems and subgenera and identify modest differences between the subgenera. This work contributes to the body of knowledge on evolution of chromosomes and the organization of genomes.