Question

How to calculate relative chromosome length?

Answer 1

Chromosome length is a basic karyotype characteristic. This paper shows, on the basis of total chromosome length (TCL) measurement, that this value is not a stable one. TCL varies among different c-metaphases from one meristem; the average TCL is different for (a) different pre-treatment agents; (b) different pre-treatment times for the same pre-treatment agents; and (c) between siblings treated simultaneously. In the same way, total chromosome volume (TCV) is not a suitable characteristic for chromosome size comparison. To solve the problem of chromosome size comparison the following standardization of TCL measurement is proposed: to determine TCL in c-metaphases with the chromosomes contracted to maximum level and still retaining all measurable karyotype characteristics. This way of standardization requires a pre-treatment method providing c-metaphases suitable for standardized TCL measurement. The paper also brings one new chromosome number to science: Onosma thracica, 2n = 14.