IRA F. GREENBAUM

Professor
Biology

Department of Biology
Texas A&M University
TAMU 3258
College Station, TX  77843-3258
Office: 216E Biological Sciences Bldg. East (map)
Phone: 979.845.7791
E-mail: i-greenbaum@tamu.edu
Department Web page

Keywords: vertebrate evolution, cytology, mammalogy

Disciplines: Evolutionary & Population Genetics, Phylogenetics & Systematics

Interests:
The research in this laboratory is focused around questions concerning chromosomal rearrangement and it role(s) in vertebrate evolution. Although this usually involves assessments of intraspecific (populational) chromosomal polymorphism, the data are generally applicable to systematic interpretations and considerable attention is paid to the phylogenetic relationships and higher taxonomic patterns of chromosomal evolution. The systematic relationships of the species studied are typically used to establish the experimental design of the hypotheses tested. Our assessments of karyotypic rearrangement and chromosomal homology involve analyses of non-differentially stained and specifically- banded metaphase chromosomes. Although deer mice (Peromyscus) are our primary model, recent projects have also addressed cytogenetic questions in birds and reptiles. The laboratory contains complete facilities for light microscopy and imaging, tissue culturing and allozymic analyses.

Recent emphasis has addressed questions concerning the meiotic effects of chromosomal mutations that are maintained as populational polymorphisms and that constitute the modes of karyotypic evolution in the organisms under study. This research has involved electron microscopic studies of the synaptonemal complex and corresponding analyses of meiotic chromosomes. Our publications in this area have documented unexpected levels of variability in meiotic pairing, meiotic mechanisms which foster the incorporation specific chromosomal mutations, unequal recombination of sex heterochromatin and a revised view of the causes and effects of chromosomal evolution.

Our current emphasis concerns the genetics and evolutionary relevance of chromosomal fragile sites. This experimental design involves mapping fragile sites within and among deer mouse populations and species. These studies are designed to document the genetic variability and evolutionary rate of chromosomal fragile sites and to determine whether these sites constitute loci which preferentially undergo chromosomal evolution.