Spirals and G-bands as a function of chromosome length.

The quantitative relationship between spirals and G-bands with regard to length has been investigated. Graphical analysis of sub-chromatid structure showed that the numbers of spirals and G-bands are directly proportional to chromosome length. Equations are derived which predict the number of G-bands or gyri appearing based on chromosome length. The width of chromatids was not found to increase proportionately in shorter chromatids. Calculations indicated that the major events occurring during chromosome contraction in metaphase are the shortening of the chromonemata, reduction in numbers of gyri and a slight reduction in unit gyrus length.