What Causes People Being left-handed?
Sunday, November 6, 2011
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So why there are still people (about 15%) are left-handed? Genetic theory presented above explains the tendency of the use of one hand side is governed by a gene that has a pair of alleles (two manifestations of the genetic properties of genes in the same location). These alleles are alleles of the gene D (short for dextra, latin language which means the right) that carry the gene trait of right-handed individuals. And the other allele is the allele of the S gene (short for the left, then left).
If an individual has a spouse DD allele, then that person will be right-handed. When individuals have a pair of alleles DS, it can be right-handed individuals or can be left-handed because the two alleles have the same properties and do not cover each other strong, so depending on the choices and habits of the individual is to be a right-handed or left-handed. And lastly, people who are left-handed individuals have a pair of alleles SS.
This theory may explain why most people are right-handed. This is because the gene D allele is more often found so more is inherited as part of an individual's genetic inheritance. On the other hand this theory can also explain the existence of right-handed children in families with parents left-handed and also the opposite of a left-handed child in a family with right-handed parents. Because, for example elderly couple who both have the DS allele (right-handed to left-handed or can be) will have a child with 4 possible combinations of pairs of alleles that DD (right handed), DS (can be also right-handed or left-handed) and SS (lefty).
Apart from genetic factors above, the trend of use of one side of the hand is also affected by external factors such as cultural factors, environmental and social. Because as described above, individuals with DS allele pairs have a chance to become right-handed or a left-handed as much. So that individual choice may be influenced by the habits of family and neighborhood where he grew flowers. Other factors such as defects of one hand may also influence the choice of hand used. Because a person would normally use the stronger parts of his body to do the activity.
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