Snow, Richard. (U. California, Davis.) Cytogenetic studies in Clarkia, section Primigenia. I. A cytological survey of Clarkia amoena. Amer. Jour. Bot. 50(4): 337–348. Illus. 1963.—Clarkia amoena (2n = 14) shows great cytological diversity based on reciprocal translocations. About ½ the plants sampled were heterozygotes; in 2 of the subspecies the frequency was as high as ⅔. The metaphase configurations were varied, including rings of 4, 6, 8, 4 + 4, 6 + 4, and more unusual types forming a chain of 3 + a univalent or a chain of 4 + a univalent. The latter have only 13 chromosomes but are not true monosomies. Some plants with supernumerary chromosomes were found, in addition to a plant with only 12 chromosomes which was derived from a “monosomic” type. From crosses of various homozygous lines to a standard strain, it was found that the standard end arrangement of chromosomes occurs widely and commonly throughout the species. A minimum of 7 different end arrangements, giving a ring of 4 with the standard strain, and 1 giving a ring of 6, account for the chromosome pairing found in interstrain crosses. No doubt more would be found with further testing. Some of the translocations may be components of adaptive polymorphic systems, though there is no proof of this yet. No balanced lethal systems similar to those in the closely related genus Oenothera were found.
Chickens sexed as females in commercial flocks show a low frequency of intersex individuals. Gross anatomical examination of the intersexes revealed malformed gonads. Histological examination proved that these gonads were not ovotestes but were composed of testicular tissues. Karyotype analysis of 15 intersex individuals showed 13 of them to be 3A-ZZW triploids (normal females are 2A-ZW) while the other 2 were mosaic for male and female karyotypes. Red blood cell volume accurately reflects the ploidy level and is suggested for use in screening for polyploids. Intersex triploids may develop parthenogenetically or from fertilization between reduced and unreduced gametes.
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