Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Eugene B. Krehbiel


The establishment of normal chromosomal patterns for a wide range of plants and animals has led to the recognition of abnormalities as well as their relationship to phenotypic irregularities. Research dealing with the expression of human karyotype is of prime interest; but, closely rivaling that is the genetic study of domestic animals which are of economic importance to man.

One observed anomaly which has come under scrutiny by cytogeneticists is that of the female member of a heterogeneous bovine twin pair, the freemartin. This is a sterile animal with internal morphology showing varying degrees of intersex. Cytogenetic studies reveal XX/XY chimerism in blood and various other tissues due to interuterine vascular anastomosis.

This study resulted in collection of the information regarding this anomaly into a relevant body of reference. Observing stained metaphase chromosomes from leukocyte cultures, experimental data were established for 109 bovine individuals, sampling the University of Illinois Dairy Research herd, the sires, and offspring. Differences were demonstrated by photomicrographs. Eight animals (7.3%) were found to carry XX/XY chimerism, only one of which was a member of a known multiple birth. The early death rate among these individuals is twice that of an average herd in Illinois. No relationship between a specific breed and appearance of this anomaly was seen.

As karyotype determinations were made, they were surveyed for other aberrations and counted to detect any variance from the normal diploid number, 2N = 60. Tetraploid-diploid mosiacism was seen in 5.5% of the animals in this study. No pathology was seen in connection with this condition. Three female animals (2.8%) carried trisomy XXX in mosiac condition with normal XX cells. Two cases (1.8%) of autosomal aneuploidy were seen, both dying of pneumonia at an early age. A Robertsonian translocation involving a centric fusion of chromosomes 1 and 29 was seen in one individual. These anomalies were demonstrated by photomicrographs.