The Heredity of Normal and Defective Colour Vision

Abstract

Forty years ago I studied the heredity of the different subtypes of the red-andgreen blindness (Waaler 1927 a and b). I tested 9049 boys and 9072 girls in the age from 8 to 13 years in the common schools in Oslo, first with Ishihara's pseudoisochromatic tables, and afterwards those who read these tables with uncertainty or as colour-blinds with the anomaloscope. With this apparatus it is possible to divide the colour-blinds into subtypes: The deuteranomals (D1 will here indicate both the gene and the property), the protanomals (PI), the deuteranopes (Dp) and the protanopes (Pp). W e also have two more subtypes, the extreme deuteranomals and the extreme protanomals between the corresponding anomals and anopes. In my old work they were classed with the anomals.It was well known that the gene of colour blindness is located in the Xchromosome, and that the normal gene in females dominates over the gene for colour blindness. Mothers with colour-blind sons, but they themselves with normal colour sense, are therefore heterozygotes (conductors) and have only one gene for colour blindness to give to (half of) their sons. I found in my material 55 groups of two to four colour blind brothers, sons of such conductors, and in all of these groups the brothers belonged to the same subtype. I also had three groups of male cousins, 2 + 1 + 1, 2 +2 and 1 + 1, where the mothers were sisters, and a group of 2+1 second cousins (boys), where the mothers' fathers were brothers, also a boy and his mother's father. In all these cases the subtypes were the same in one family group. From these facts I could draw the conclusion that the four subtypes were inherited as distinct mutants,

The Unique Green phenomenon and colour vision

“…The dip for the males is significant, P = 0.01, and remains so with all simple transformations of the data. Waaler (1967) showed with a large number of pedigrees that this is due to a single effect, carried on the X chromosome, which breeds true, neither condition being dominant to the other. Thus in the male, the two homozygous conditions correspond to the two modes, with a distinct gap in the frequency distribution, whereas in the female, although the two homozygous conditions would manifest distinctly, the heterozygotes are intermediate and fill the gap.…”

“…GI and G;1 are used to denote the possible genotypes for the male, according t o which mode Unique Green group he belongs. G11 and G a are the possible genotypes for fe- Tabie 1 for females for the Class on Richards' (1967) notation for females for the Class on Richards (1967) Table 3 Genotypes of fathers and mothers producing daughters of particular genotypes: the daughters have genotypes which can arise from the X chromosome males, which correspond to the male G1 and G2, respectively, and G12 forms an intermediate group with a small overlap (see Waaler 1967, Cobb 1973).…”

“…The pedigrees were tested by an apparatus slightly different from that described above, since the laboratory spectrometer, which had been developed to give as clear-cut a result as possible, could not be transported to the locations of the families concerned without risk of damage and disturbance to the calibration. The apparatus used for the pedigrees was a Nagel 11 anomaloscope similar to that used by Waaler (1967), and his single field technique was repeated. This involved setting the luminance and mixture screws at zero and asking the subject to set the upper field, by means of the main screw, until the colour seen was neither blue-green nor yellow-green but green-green.…”

“…This is discussed at length by Cobb (1973); in brief, all unsuccessful experiments involved a field of 2" or less and there was no comparison field. The successful techniques listed above all involved fields of angular subtense greater than 2", and in some cases of Waaler's (1967) bipartite field technique and the present spectrometer technique, there was a comparison field.…”

Performance of normal females and carriers of color-vision deficiencies on standard color-vision tests

“…But many carriers present with a slight or moderate reduction in color vision in that they make more errors on the Ishihara test than normal trichromatic subjects do (for an overview of previously published results, see Table 1). Some carriers may also exhibit a shift in Nagel match midpoint (MMP) and an enlarged Nagel matching range (MR) when tested by Rayleigh anomaloscopy [2,[6][7][8][9]. Protan carriers are less sensitive to red light, a characteristic known as Schmidt's sign [6,[10][11][12].…”