Morton's Toe: Prevalence and Inheritance Pattern among Nigerians

BACKGROUND: Anatomical variations have been genetically linked and the difference in the length of the big toe relative to the second toe (Morton's toe) is not an exception; however, its prevalence and inheritance pattern has been a scientific debate. Therefore, this study investigated the prevalence and inheritance pattern of Morton's toe among Nigerians in Rivers State. MATERIALS AND METHODS: A total of 101 families comprising of 101 parents (fathers and mothers) and 135 offspring were conveniently sampled for this study. The observed big toe pattern was described as “L(BT)” and “S(BT)” representing big toe longer than the second toe and big toe shorter or equal to the second toe, respectively. The offspring trait was tabulated alongside the parental combination patterns (i.e., when both parents had L(BT), both parents S(BT)and a combination of L(BT)and S(BT)). XLSTAT 2012 (version 4.2.2) Chi-square analysis tested the association between sex and Morton's toe. Mendelian Chi-square gene distribution model evaluated the conformance to simple dominance-recessive pattern, while the Hardy–Weinberg (H-W) equation for allele frequency compared the parental allele frequency to that of the offspring. RESULTS: L(BT)(218; 64.7%) was more in the studied population than S(BT)(119; 35.3%); with males (63; 18.7%) having slightly higher proportion of SBT (Morton's toe) than females (56; 16.6%), which was without sexual preference (χ(2) = 0.141, P > 0.932). The test of offspring gene distribution in conformance to Mendelian simple dominant-recessive monohybrid cross had rather weak result. The H-W equation showed a deviation of offspring allele distribution (1:3:2.5 [2:6:5]) from the parents (1:3:2). CONCLUSION: Morton's toe could be said to be genetically linked, however, its inheritance pattern does not conform to the simple dominant-recessive model, but a more complex pattern. It should be noted that the large frequency of a trait in a population does not make it dominant.