Aspects of evaluation, significance, and evolution of human C-band heteromorphism.

The C-band heteromorphism may be evaluated in different forms. The results obtained from classification are easily influenced by subjective factors, and the conclusions of such types of data are acceptable only if they are well matched with a control. The length measurement is simple to obtain, and a quantitative presentation of the data, with correction for the contraction stage of the chromosomes, is considered the most efficient method to evaluate the C-band size heteromorphism. Excluding the acrocentrics, whose short arms present a complex heteromorphism, and the chromosome Y, whose variable C band is terminal, all others present C-band location heteromorphism except pair 16. It is possible to multiply the detectable heteromorphisms in some bands by using diverse staining methods. The present state of knowledge about the role of heterochromatin in the cell is analyzed, as is the effect of C-band variability on the phenotype, the reproductive fitness, and the individual viability. Although a great amount of data is available, no result can be considered definitive as yet. Aspects in which the use of C-band heteromorphisms are profitable are considered.