[Texts]

Date:
1971
Reference:
PP/CRI/H/5/1/1
Catalogue details

Licence: In copyright

Credit: [Texts]. Source: Wellcome Collection.

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    The model, in its simplest form, suggests that the number of different proteins normally produced by higher organisms may not be much more than a few thousand for Drosophila and some tens of thousands for man. However it is not completely excluded that, in special cases, multiple coding sequences may be hidden within some of the globular bands, in which case the numbers could be higher. The amount of these special bands, if they exist, might differ markedly in different kinds of higher organisms. The model, which is logically coherent, appears to me to be compatible with a very large amount of experimental data obtained using very different techniques. These include rough estimates from genetic data of the number of genes in Drosophila and man, the correlation between the \0¡ number of bands-plus-interbands and genetic complementation groups, the % specific pairing between the bands of the giant polytene chromosomes 15,/¿,17 shown by the study of invertions, etc., the nature and general effects lo of the heterochromatin, the large amount of data on nucleic acid 2,21 hybridisation and the formation of circles by the technique of Thomas It can also be accommodated to the data on the puffing of polytene 5 chromosomes, the general nature of the heterogeneous rapidly turning 2% over nuclear RNA and the apparent absence of polycistronic messengers in higher organisms. It is not incompatible with the very scanty X-ray _ )] studies of chromatin and the electron microscope pictures and measurements. Although the model is £i»^fc-a-general--&ne cuhá , & aìfehou-gh ^ raises at least as many questions as it^answers, I hope it may serve as a focus for discussion and for the design of experiments.
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