Change in the magnitude of meiotic drive due to increased temperature

Abstract

While major changes to chromosomal form is generally deleterious, karyotypes are not static. Major chromosomal rearrangements contribute to genetic isolation and divergence within and between species. As mechanisms that drive these divergences have not been fully elucidated. We hypothesize that meiotic drive, ie. bias transmission from parent to offspring, has contributed to the reshaping of karyotypes. Drosophila americana and Drosophila novamexicana are sister species that are an excellent model to study such evolutionary forces. Since diverging from D. novamexicana, D. americana has had two major chromosomal rearrangements: centromere fusions between the 2nd and 3rd chromosomes and the X and 4th chromosome. The X-4 chromosome has remained polymorphic. It is found in a latitudinal gradient along the Mississippi River. Northern populations contain more of the fused arrangement while southern populations have more of the unfused arrangement. With meiotic drive favoring the X-4 chromosome, it should fix in the population. There are two leading hypotheses explaining the polymorphic nature of the X-4 fused chromosome. First, the meiotic drive is only activated in times of stress, which is more consistent in Northern populations. Second, Meiotic drive occurs in all flies, but selection against the fused X-4 chromosome is high in climates that are more associated with the Southern United States. This study was intended to identify if increased temperature affects meiotic drive. We measured inheritance patterns from heterozygous females to offspring at an increased temperature. Then the offspring’s DNA was extracted. PCR and Gel electrophoresis was done to identify which chromosome was inherited.