Research Interests
My research takes several separate, but mutually reinforcing approaches to study the role which certain genetic defects of meiosis may play in affecting the population dynamics and evolution of natural populations. We use the insect Drosophila melanogaster as a model organism.

Evolution of Mendelian segregation and a balanced sex ratio. Our primary interest is the mapping and molecular dissection of a genetic system causing death of sperm carrying a specific satellite DNA sequence (Rsp). his can lead to a reduced recovery of genetic markers linked to Rsp, and a violation of the expected 1:1 Mendelian segregation ratio for heterozygous alleles. This phenomenon is called meiotic drive. Besides studying the relationship between sperm death and level of satellite sequence divergence and copy number,we use chromosomal rearrangements to dissect the region of heterochromatin where Rsp is located for molecular mapping purposes. Such rearrangements also allow us to move the Rsp satellite sequences to other genetic locations where they cause meiotic drive to be directed against their new chromosomal home. For example, such constructs can be used to cause sex ratio distortion (in either direction), allowing us to study the impact of abnormal sex ratios on experimental populations, and to survey how suppressors and enhancers of drive may evolve to stabilize the 1:1 Mendelian segregation ratios.

Transposable elements and evolution of chromosome rearrangements. We are also interested in the forces affecting the evolution of linkage combinations and chromosome structure in natural populations. We use computer models and population cages to investigate the impact of meiotic drive systems on fitness and genetic polymorphism, and on the evolution of chromosome rearrangements and the sex ratio. In addition, we are interested in the evolution of transposable elements in natural populations of Drosophila, and what role they may have in altering chromosome structure. In particular, we are studying the role of P and hobo transposable elements in mediating the hypermutability exhibited by some chromosomes taken from Hawaiian populations of D. melanogaster. This involves both an assessment of the distribution of these elements in the genome, as well as a molecular analysis of the structure of P and hobo elements at mutational hotspots and at the breakpoints of newly arising inversions in nature. We hope the results from these studies will be applicable to understanding the population genetics and evolutionary biology of endemic, endangered species of Hawaiian Drosophila.

For both these areas of research, we employ integrative approaches involving molecular genetic analysis, mutagenesis, classical genetic mapping and analysis, cytogenetic manipulation, and evolutionary modeling with both computer and population cages.

Lyttle, T. W. (1993). Cheaters sometimes prosper: Distortion of Mendelian segregation by meiotic drive systems. Trends in Genetics 9:205-210.

Lyttle, T. W. and D. S. Haymer (1992). The role of the transposable element hobo in the origin of endemic inversions in wild populations of Drosophila melanogaster. Genetica 86:113-126.

Lyttle, T. W., C.-I Wu, and R. S. Hawley (1992). Molecular analysis ofinsect meiosis and sex ratio distortion. In: Molecular Approaches to Pure and Applied Entomology , pp. 357-406, Springer/Verlag, New York.

Lyttle, T. W. (1991). Segregation Distorters. Annu. Rev. of Genet. Applied Entomology , pp. 357-406, Springer/Verlag, New York.

Lyttle, T. W. (1991). Segregation Distorters. Annu. Rev. of Genet. 25:511-557.

Temin, R. G.; Ganetzky, B.; Powers, P.; Lyttle, T. W.; Pimpinelli, S.; Wu, C.-I and Y. Hiraizumi (1991). Segregation distorter (SD) in Drosophila melanogaster: Genetic and molecular analyses. Amer. Nat. 137:287-331.

Walker, E. S.; Lyttle, T. W. and J. C. Lucchesi (1989). Transposition of the Responder element (Rsp) of the Segregation distorter system (SD) to the X chromosome in Drosophila melanogaster. Genetics 122:81-86.

Lyttle, Terrence W. (1989). Is there a role for meiotic drive in karyotype evolution? (In: Genetics, Speciation and the Founder Principle, Kaneshiro, Giddings and Anderson, eds. Oxford University Press).

Lyttle, Terrence W. (1989). The effect of novel chromosome position and variable dose on the genetic behavior of the Responder (Rsp) element of the Segregation distorter (SD) system of D. melanogaster. Genetics 121:751-763.