AMINO ACID CONSTITUTION OF CHROMOSOMES

The present experiment was designed to demonstrate the presence of two protein-bound amino acids, viz. tryptophan and tyrosine, in the different, cellular constituents with particular reference to chromosomes. The materials chosen were the root-tips of Allium cepa and Vicia faba. Studies were made from the smeared tissue preparation. For tryptophan, indole reactions following two methods, viz., that of Gurr (1958) and of Glenner and Lillie (1957) were followed and the latter yielded satisfactory results; while for tyrosine, Bensley and Gersh's modified Millon's reaction (1953) was adopted. The results of the reactions show that tryptophan is present in much less amount than tyrosine in the protein component of the chromosomes. The same is true with cytoplasm as well. The strongly positive tyrosine reaction of nuclear membrane, with distinct strands towards the cell membrane, has been attributed to its role in nucleocytoplasmic transfer and synthesis of cytoplasmic protein. The less positive reaction of nuclear membrane with tryptophan suggests its comparatively little importance in transfer. Only in case of tyrosine, the differential reaction of the euchromatic and heterochromatic parts could he made out, the latter giving negative response. It has been suggested that it might appear only during the time of transfer through the nucleolus. Tryptophan on the other hand shows uniform distribution throughout the chromosome length.