Relative optical path differences of the colchicine-metaphase chromosomes of the Chinese hamster, Cricetulus griseus

Summary

• 1. Relative optical path differences were determined for colchicinemetaphase chromosomes of the Chinese hamster.

• 2. In a predominantly diploid cell culture of adult female origin, there was a small background of variability consistently present among the optical paths of the chromosomes of any one cell.

• 3. One-half of the cells of the diploid culture had one or two chromosomes differing highly in optical retardation from the rest of the complement.

• 4. In 65 per cent of the variant cells of the diploid culture, it was a subtelocentric chromosome that had a much longer optical path, and in 35 per cent, a small metacentric.

• 5. In an aneuploid culture derived from a mixed embryo culture, there were also small phase differences from chromosome to chromosome, probably equivalent to those seen in the female, diploid culture.

• 6. In forty per cent of the colchicine metaphases of the aneuploid culture, a long metacentric chromosome showed a marked tendency to have a different retardation through its two arms.

• 7. There were also differences in retardation through the chromosomes of non-colchicinized, control metaphases of the diploid culture; so the optical variability is not an effect solely of colchicine.

• 8. Technological problems involved in interferometric measurements at the chromosome level are discussed.

• 9. The interpretation of the interference patterns of chromosomes is considered in relation to: 1. chromosome condensation and coiling of chromatids; 2. volume of the chromosomes; 3. effect of colchicine; 4. composition of the chromosomes.

• 10. The biological significance of the metaphasic interference patterns of chromosomes is discussed.