transposition

1. Removal from one place to another; metathesis. 2. The condition of being in the wrong place or on the wrong side of the body, as in t. of the viscera, in which the viscera are located opposite their normal position; e.g., the liver on the left, the apex of the heart on the right. 3. Positioning of teeth out of their normal sequence in an arch.

- t. of arterial stems SYN: t. of the great vessels.

- corrected t. of the great vessels anatomically or physiologically corrected malposition of the great arteries. In anatomically corrected t., they arise from the correct ventricles but have an abnormal relation to each other (actually a malposition rather than a t..) In physiologically or functionally corrected t., the aorta arises from a systemic ventricle that has the morphologic characteristics of a right ventricle, and the pulmonary artery arises from a “venous” ventricle that has the morphologic characteristics of a left ventricle.

- t. of the great vessels congenital malformation in which the aorta arises from the morphologic right ventricle and the pulmonary artery from the morphologic left ventricle resulting in two separate and parallel circulations. The condition is lethal unless some communication exists between the systemic and pulmonic circulation after birth; otherwise, unoxygenated venous blood inappropriately enters the systemic circulation, and oxygenated pulmonary venous blood is inappropriately directed to the pulmonary circulation. The life-sustaining communication may be an intraatrial passage or a patent ductus arteriosus. SYN: t. of arterial stems.

- penoscrotal t. a developmental error, seen with hypospadias, whereby hemiscrotal units are separated and lie lateral to the penile shaft or even cranial to it.

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trans·po·si·tion .tran(t)s-pə-'zish-ən n an act, process, or instance of transposing or being transposed: as

a) the displacement of a viscus to a side opposite from that which it normally occupies <\transposition of the heart>

b) the transfer of a segment of DNA from one site to another in the genome either between chromosomal sites or between an extrachromosomal site (as on a plasmid) and a chromosome

trans·po·si·tion·al -'zish-nəl adj

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n.

the abnormal positioning of a part of the body such that it is on the opposite side to its normal site in the body. For example, it may involve the heart (see dextrocardia).

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trans·po·si·tion (trans″po-zĭґshən) [trans- + position] 1. any of various congenital anomalies in which organs are displaced to the opposite side from normal. 2. the operation of carrying a tissue flap from one situation to another without severing its connection entirely until it is united at its new location. 3. the exchange of position of two atoms within a molecule. 4. movement of genetic information from one locus to another, such as via a transposable element.