By Susumu Ohno
Typical choice operates between person organisms which range of their genetic structure. The measure of hereditary variability inside a species is vastly more suitable by way of cross-fertilization. certainly, the mechanism of sexual replica happened very early in evolution, for it's visible this day even in micro organism. In Escherichia coli, fertilization happens by way of passage of the one chromosome from the male into the feminine bacterium (LEDERBERG, 1959). In multicellular organisms, the separation of germ from soma, and the construction of haploid gametes turned necessary. The gametes have been of 2 varieties. One, super cellular, was once designed to find and penetrate the opposite, which loaded with foodstuff, acquired the cellular gamete and intiated the advance of a brand new person. the basis for precise bisexuality was once therefore laid. within the primitive kingdom of bisexuality, no matter if anyone is to be a sperm-producing male or an egg-producing woman seems to be determined really haphazardly. within the bug, Banelia viridis, the minute men are parasites within the girl. Larvae that develop into connected to the proboscis of an grownup lady develop into men, whereas unattached larvae sink to the ground and turn into ladies (BALTZER, 1935). The extra refined nation of bisexuality was once initiated by way of environment apart a selected pair of chromosomes for specialization and making both the male or the feminine a heterogametic intercourse. intercourse chromosomes as we all know them have been hence born.
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28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. Partial color blindness, deutan series Partial color blindness, protan series Total color blindness Glucose-6-phosphate dehydrogenase deficiency Xg blood group system Muscular dystrophy, Dumenne type Muscular dystrophy, Becker type Hemophilia A Hemophilia B Agammoglobulinemia Huder syndrome Late spondylo-epiphyseal dysplasia Aldrich syndrome Hypophosphatemia Hypoparathyroidism Nephrogenic diabetes insipidus N eurohypophyseal diabetes insipidus Low's oculo-cerebro-renal-syndrome Hypochromic anemia (Cooley-Rundles-Falls type) Angiokeratoma diffusum corporis universale Dyskeratosis congenita Dystrophia bullosa hereditaria, typus maculatus Keratosis follicularis spinulosa cum ophiasi Imthyosis vulgaris Anhidrotic ectodermal dysplasia Amelogenesis imperfecta, hypomaturation type Amelogenesis imperfecta, hypoplastic type Absence of central incisors Congenital deafness Progressive deafness Mental deficiency Börjeson syndrome Spinal ataxia Cerebellar ataxia with extrapyramidal involvement Spastic paraplegia Progressive bulbar paralysis Charcot-Marie-Tooth peroneal muscular atrophy Diffuse cerebral sclerosis (Pelizaeus-Merzbacher) Diffuse cerebral sclerosis (Scholz) Hydrocephalus Parkinsonism Problems of Genocopies in Seeking Homology of the X-linked Genes Table 2 (continued).
Cytological Evidence of Conservation 47 Various evidences presented in Chapters 1 and 2, on the other hand, revealed that the differentiation of the X and the Y from a homologous pair was accomplished at the expense of the heterogametic sex determiner. While the Y shed Mendelian genes which were originally on it, all these genes were conserved by the X. Conservation of the original X within the stable genome implies that there should be extensive homology of the X-linked genes among placental mammals, for so-called X-linked genes are the Mendelian genes wh ich were already there when the X was merely a member of an ordinary homologous pair.
PENNOCK, L. : Triploidy in parthenogenetic species of the Teiid lizard, Genus Cnemidophorus. Science 149, 539 (1965). SAEZ, F. , and N. BRUM: Citogenetica de anfibios anuros de America del Sur. An. Fac. Med. Montevideo 44, 414-423 (1959). UZZELL, T. : Natural triploidy in salamanders related to Ambystoma jeffersonianum. Science 139, 113-115 (1963). VAN BRINK, ]. : L'expression morphologique de la Digametie chez les Sauropsides et les Monotremes. ) 10, 1-72 (1959). Chapter 4 Conservation of the Original X and Homology of the X-linked Genes in Placental Mammals Comparative DNA values of various vertebrates eonsidered in Chapter 3 have indieated the polyphyletie origin of vertebrate genomes.