Organization of constant region genes

In the mouse, the IgH locus comprises eight CH genes on an approximately 200 kb region [9,10,11]. The JH cluster consists of four J segments and lies 6.5 kb upstream of CM with the D-Q52 segment located 0.7 kb upstream of JH1 [11,12]. The 

Distances between mouse [9,10,11] and human [31,32,33,34,35,206,37] constant region genes 

There is only one copy of the CK gene in mouse and this is located about 3 kb downsteam of the JK cluster [15,16], The k locus contains a few hundred VK genes [17] and five JK segments, one of which (JK3) appears to be non-functional as it carries an unusual splice site and has never been found to be expressed in protein (Fig. 2) [18,19], 

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