Heredity and Line A of Palmar Dermatoglyphics

EDWARD V. GLANVILLE

Department of Medical Genetics,Cleveland Psychiatric Institute,

Cleveland, Ohio.

PATrERNS FORMED BY the dermal ridges on the palm show considerable vari-ation. Ethnic differences have been observed (Cummins and Midlo, 1961)and a number of features have been found to occur with distinctive fre-quencies among individuals with certain congenital defects, particularlythose associated with chromosomal aberrations, such as mongolism, Turner'ssyndrome, and the trisomy 13-15 syndrome (Penrose, 1963).At the base of each digit, with the exception of the thumb, there is typical-

ly a triradius or meeting point of three opposing ridge systems. These fourtriradii are designated by the letters a to d in radio-ulnar sequence. Ridgetracings extended from them are known as main lines, individually designatedby the corresponding capital letters. Line A accordingly is the main line whichhas its origin in triradius a at the base of the index finger (Fig. 1).

Line A is considered to be an important indicator of the general directionof ridges coursing over a large area of the palm (Weninger, 1963). Its cours-ing varies widely between the extremes of transverse and longitudinal. Ittends to follow a more transverse course in mongoloid mental defectives thanin unaffected subjects (Cummins, 1939). By contrast, an extreme longitudinalarrangement has been observed to occur in association with multiple con-genital malformations and apparently normal karyotype (Wolf, Brehme, andReinwein, 1964).An attempt has been made in the present study to investigate the influence

of heredity on the course followed by line A as it crosses the palm in subjectsfrom the general population. A quantitative estimate of its direction has beenobtained by counting the number of dermal ridges intervening betweentriradius d and line A at a standard distance from its origin. This ridge count,called here the A-d ridge count, has been used in pedigree studies. The degreeof likeness between family relatives has been measured by calculation of thecorrelation coefficient using the total A-d ridge count, that is, the combinedcount for left and right hands. The A-d ridge count is predominantly a mea-sure of the deviation of line A from a transverse course. However, the rela-tive density of the dermal ridges will also influence the count to a limitedextent.

MATERIALS AND METHODS

The sample consisted of families and pairs of twins from the Cleveland

Received April 8, 1965.Supported by U. S. Public Health Service grants NIH 07820, HD 00581, GRS 05251,

and GRS 05563 from the National Institutes of Health.

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AMERICAN JOURNAL OF HUMAN GENETICS, VOL. 17, No, 5 (SEPTEMBER), 1965

GLANVILLE

FIG. 1. The A-d dermal ridge count. The A line is shown crossing the palm, and theline along which the A-d count is made is indicated by a double-headed arrow.

area. Contact with the majority of families was established through localtwin clubs. The remainder of the sample consisted of families and friendsof individuals on the staff at the Cleveland Psychiatric Institute. All were ofEuropean descent and all were apparently free of congenital defect. The sam-ple included 115 family groups. In addition, 28 isolated twin pairs and sevenfamilies in which one or the other parent was not available were included.The age of the youngest subject was five years. Zygosity of the twins was de-termined by examination of nondermatoglyphic morphological features andby comparison of the ABO, MNS, Rh, Kell, Fya, Jka, and P blood factors.The A-d ridge count was made by tracing line A from its source in triradius

a according to the principles described by Cummins and Midlo (1961, pages87 and 88). A compass was then used to draw an arc which had triradius aat its center, through triradius d to the point where the arc cut line A. Thenumber of dermal ridges crossed by a straight line drawn between triradiusd and the point where the arc cut line A was then determined. This numbernumber has been referred to as the A-d ridge count (Fig. 1).

RESULTS AND DISCUSSION

The A-d counts on left and right hands of the observed population areshown in Fig. 2. The mean count on the left hand was significantly largerthan on the right by approximately nine ridges (P < .01). This bilateralasymmetry of line A, which was evident in both sexes, is well known (Cum-mins and Midlo, 1961).The distribution of the total ridge counts on both hands of 315 female

and 292 male members of our population are shown in Fig. 3. These histo-

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PALMAR DERMATOGLYPHICS

N 607MEAN=53-8 LEFT

S.D.= 14-1

N'607MEAN-44 9

S.D.= 12-3

FIG. 2. The A-d ridge count on left and right hands of 292 males and 315 females.

grams include data from family groups and twins and are not nec-essarily representative of the general Cleveland population. Normal curvescomputed to have the corresponding means and standard deviations havebeen superimposed on the observed distributions in Fig. 3. The observedfrequencies do not deviate significantly from the normal distributions eitherin skewness or kurtosis. The mean value in males was five ridges larger thanin females. This difference is statistically significant (P < .05), but no ad-justment has been made for it and the data have been used without the in-troduction of correction factors for sex.The correlation coefficients for the total A-d ridge counts observed among

relatives are given in Table 1. Monozygotic twins showed closely similarcounts, and the correlation coefficient was found to be 0.94 ± 0.02. The sib-sib correlation was 0.44 + 0.04 and for dizygotic twins 0.39 + 0.13. Theparent-child correlation was 0.48 ± 0.03, which was not significantly differ-ent from the sib-sib. Dominance would be expected to decrease the parent-child correlation relative to the sib-sib, and, since the observed values arewithin the same range, dominance does not appear to be a significant factorin the inheritance of this trait. If it is assumed that the total variation is due

TABLE 1. CORRELATIONS BETWEEN RELATIVES FOR TOTAL A-d RIDGE COUNTRelationship Correlation Coefficient Number of Pairs Used

Father-Mother 0.06 + 0.09 115 (from 115 families)Father-Son 0.46 ± 0.07 134 (from 82 families)Father-Daughter 0.44 ± 0.07 153 (from 81 families)Mother-Son 0.52 + 0.06 140 (from 85 families)Mother-Daughter 0.52 ± 0.06 162 (from 85 families)Parent-Child 0.48 ± 0.03 589 (from 122 families)Midparent-Child 0.65 ± 0.03 284 (from 115 families)Son-Son 0.35 + 0.10 85 (from 41 families)Daughter-Daughter 0.42 ± 0.08 119 (from 52 families)Son-Daughter 0.54 ± 0.06 147 (from 57 families)Sib-Sib 0.44 ± 0.04 351 (from 101 families)Monozygotic Twins 0.94 ± 0.02 36 (from 36 families)Dizygotic Twins 0.39 ± 0.13 40 (from 40 families)

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to hereditary factors, genes of additive effect acting without dominance wouldbe expected to give correlation coefficients of 0.5 for both parent-child andsib-sib comparisons (Fisher, 1918). The observed values agree closely withthis figure. Under the same conditions, the theoretical correlation coefficientfor child and midparent (i.e., the average of the parental measurements) is0.71 (Penrose, 1949). The observed value was 0.65 + 0.03.

Assortative mating was not of importance in these families as the mother-father correlation was not significantly different from zero. When the parent-child and sib-sib correlations were analyzed according to sex, there was noevidence of sex-linked inheritance (Table 1).

Calculation of the correlation coefficients between relatives for both thetotal finger ridge count (Holt, 1961) and the a-b ridge count (Pons, 1964)have yielded values in close agreement with those expected on theoreticalgrounds for polymeric systems with genes of additive effect. The A-d ridgecount appears to resemble the a-b and finger ridge counts in that variationin this feature is largely under genetic control and subject to the influenceof genes with additive effect.

SUMMARY

An estimate of the direction followed by the line A dermal ridge as itcrosses the palm was obtained by counting the number of dermal ridges in-terening between triradius d and line A at a standard distance from its ori-gin in triradius a. The correlation coefficient method was used to investigatethe likeness in ridge count between twins and other family members.The correlation between monozygotic twins was observed to be 0.94 + 0.02

and between siblings 0.44 ± 0.04. The parent-child correlation was 0.48 +

0.03 and the midparent-child 0.65 + 0.03. There was no evidence of sex-linkageand variations in the trait appeared to be predominantly under genetic con-trol and under the influence of a polymeric system of genes with additiveeffect.

REFERENCESCUMMINS, H. 1939. Dermatoglyphic stigmata in mongoloid imbeciles. Anat. Rec. 73:

407-415.CUMMINS, H., AND MIDLO, C. 1961. Finger Prints, Palms, and Soles. New York: Dover

Publications.FISHER, R. A. 1918. The correlation between relatives on the supposition of Mendelian

inheritance. Trans. Roy. Soc. Edinb. 52: 399-433.HOLT, S. B. 1961. Quantitative genetics of finger-print patterns. Brit. Med. Bull. 17:

247-250.PENROSE, L. S. 1949. The Biology of Mental Defect. London: Sidgwick and Jackson.PENROSE, L. S. 1963. Finger-prints, palms, and chromosomes. Nature 197: 933-938.PONS, J. 1964. Genetics of the a-b ridge count on the human palm. Ann. Hum. Genet.

(Lond.) 27: 273-277.WENINGER, M. 1963. Die Bedeutung der Linie A im Hautleistensystem der menschlichen

Palma. Proc. 2nd International Congr. Hum. Genetics (Rome, 1961) 3: 1517-1526.WOLF, U., BREHME, H., AND REINWEIN, H. 1964. Zum Thema: Longitudinale Leisten-

verlaufe auf der Handflache des Menschen. Humangenetik 1:149-156.

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