Hand clasping is the superposition of each

finger A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers (Pentadactyly). Chambers 1 ...

of one

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each " ...

over the corresponding finger of the opposite hand. When clasping the hands, a person tends to interlace the fingers in one of two ways. People who hold the fingers of the right hand above the left fingers are classified as

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prop ...

''R'' (right), while those who hold the fingers of the left hand above those of the right are phenotype ''L'' (left). Although some people do not exhibit a preference for one type of hand clasping, most do. Once adopted, the method of hand clasping tends to be consistent throughout life. When an individual attempts to clasp the hands in the opposite configuration from the usual one, that person may feel a sense that something is out of the ordinary. Lai and Walsh (1965) suspect that genetic factors are important in determining these characteristics. They looked at a sample of 18 families. Based on the comparison of a series of monozygotic and dizygotic

twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...

, Freire-Maia (1961) concluded that the preference in the type of hand clasping was affected by certain genetic factors, and (perhaps) to a significant extent. Falk and Ayala (1971) found a significant correlation between parent-offspring and for this feature suggested model polygenic inheritance. Martin (1975) presented the results of studies of

and found that genetic factors are still determining the phenotypic expression of this trait. Reiss (1999) found that 55% of the

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using ...

belongs to the phenotype ''L'', and 44% have a "right type" clasping; the remaining 1% did not care. In support of the hypothesis about the significant influence of genetic factors on the phenotypic expression of the extreme

dimorphism Dimorphism or dimorphic may refer to: Science * Dimorphic root systems, plant roots with two distinctive forms for two separate functions * Sexual dimorphism, a phenotypic difference between males and females of the same species * Nuclear dimorph ...

clearly demarcated by the data on a very wide range of variation in the frequency of phenotypes tested parts of the world's population.

''R'' phenotype distribution

References

{{reflist

External links

* http://learn.genetics.utah.edu/content/inheritance/observable/ (en) Hand gestures Classical genetics Human population genetics

''R'' phenotype distribution

See also

References

External links