Comparative Morphometric Analysis of Primate Chromosomes I. The Chromosomes of Anthropoid Apes and of Man

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Abstract
In a research programme on the karyological aspects of evolution in Primates the author in the present paper shows the results of a morphometric comparative analysis between the chromosomes of Man and the Anthropoid Apes. The chromosome number in the three genera of Apes (Gorilla, Pan and Pongo) in the somatic mitosis is always 48. The average lengths in μ of the karyotypes analysed in detail are as follows: Homo 93,7 ±19,3 Pan 94,1 ± 9,1 Pongo 83,6 ±11,4 The comparative study of each single chromosome showed the similarity in dimension and morphology among some chromosomes of the various species. The sex chromosomes were studied from a comparative point of view. The Y chromosome is, in every case, one of the smallest of the set. While in Man, Chimpanzee and Gorilla it appears to be eucromatic along its entire length, in Orang-utan it has a big achromatic portion in its small arm. The position of the centromere is submetacentric in Pan, Homo and Pongo. The X cromosome seems to be one of the largest of the set in Gorilla and its centromere position appears to be metacentric. The X chromosome of the Chimpanzee is also one of the largest chromosome and it is nearly metacentric. The X chromosome of the Orang-utan looks very similar in size and morphology, to that of Man. Different reasons lead us to suppose that the variation in the number of chromosomes from 48 in Anthropoids to 46 in Man may have originated by a centric fusion of two subterminal chromosomes in a ancestral Prehominoide.