Profile Photo of Ira Greenbaum
Ira Greenbaum

Professor Emeritus

Fax: 979-845-2891

Joined the Department in 1978

  • B.A., 1973, Hofstra University, Biology.
  • M.S., 1975, Texas Tech University, Zoology.
  • Ph.D., 1978, Texas Tech University, Zoology.



Vertebrate Cytogenetics

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 emphases concern the genetics and evolutionary relevance of chromosomal fragile sites and continued studies of the systematics and evolution of the Peromyscus maniculatus species group. This former 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. The latter reflects our continued interest in the evolution of deer mice and the use of these as model species for examining character state evolution.

  1. Walker, ML, Chirhart, SE, Moore, AF, Honeycutt, RL, Greenbaum, IF. Genealogical concordance and the specific status of Peromyscus sejugis. J Hered. 2006;97 (4):340-5. doi: 10.1093/jhered/esl007. PubMed PMID:16785280 .
  2. Chirhart, SE, Honeycutt, RL, Greenbaum, IF. Microsatellite variation and evolution in the Peromyscus maniculatus species group. Mol Phylogenet Evol. 2005;34 (2):408-15. doi: 10.1016/j.ympev.2004.10.018. PubMed PMID:15619451 .
  3. Denison, SR, Simper, RK, Greenbaum, IF. How common are common fragile sites in humans: interindividual variation in the distribution of aphidicolin-induced fragile sites. Cytogenet Genome Res. 2003;101 (1):8-16. doi: 10.1159/000073411. PubMed PMID:14571130 .
  4. Dahm, PF, Olmsted, AW, Greenbaum, IF. Probability models and the applicability of statistical procedures in the identification of chromosomal fragile sites. Biometrics. 2002;58 (4):1028-31; discussion 1032-3. doi: 10.1111/j.0006-341x.2002.01028.x. PubMed PMID:12495159 .
  5. Berend, SA, Hale, DW, Engstrom, MD, Greenbaum, IF. Cytogenetics of collared lemmings (Dicrostonyx groenlandicus). II. Meiotic behavior of B chromosomes suggests a Y-chromosome origin of supernumerary chromosomes. Cytogenet Cell Genet. 2001;95 (1-2):85-91. doi: 10.1159/000057023. PubMed PMID:11978976 .
  6. Chirhart, SE, Honeycutt, RL, Greenbaum, IF. Microsatellite markers for the deer mouse Peromyscus maniculatus. Mol Ecol. 2000;9 (10):1669-71. doi: 10.1046/j.1365-294x.2000.01044-6.x. PubMed PMID:11050566 .
  7. Smith, LR, Hale, DW, Greenbaum, IF. Systematic implications of chromosomal data from two insular species of Peromyscus from the Gulf of California. J Hered. 2000;91 (2):162-5. doi: 10.1093/jhered/91.2.162. PubMed PMID:10768134 .
  8. Dawson, WD, Young, SR, Wang, Z, Liu, LW, Greenbaum, IF, Davis, LM et al.. Mus and Peromyscus chromosome homology established by FISH with three mouse paint probes. Mamm Genome. 1999;10 (7):730-3. doi: 10.1007/s003359901080. PubMed PMID:10384049 .
  9. Greenbaum, IF, Fulton, JK, White, ED, Dahm, PF. Minimum sample sizes for identifying chromosomal fragile sites from individuals: Monte Carlo estimation. Hum Genet. 1997;101 (1):109-12. doi: 10.1007/s004390050596. PubMed PMID:9385380 .
  10. McAllister, BF, Greenbaum, IF. How common are common fragile sites: variation of aphidicolin-induced chromosomal fragile sites in a population of the deer mouse (Peromyscus maniculatus). Hum Genet. 1997;100 (2):182-8. doi: 10.1007/s004390050487. PubMed PMID:9254846 .
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