PHOTOMETRIC DETERMINATION OF DNA IN HUMAN CHROMOSOMES

A photographic colorimetric method was used to determine the amount of DNA in both human metaphase plates and individual chromosomes. The combination of photographic colorimetry calibrated with a DNA-containing model system and a new procedure for spreading human chromosomes gave DNA contents that are in rather good agreement with the biochemically determined values. It was found that the techniques commonly used to spread chromosomes result in a considerable loss of DNA. The data in the literature on DNA measurements of chromosomes are compared with our results. The coefficients of replication of the present data for the individual chromosomes range from 2 to 6 per cent, depending on the size of the chromosomes. The DNA content of the chromosomes proved to be a more constant identification parameter than length measurements. © 1968.