USMLE Q. t(A,B) means translocation fr. A to B or B to A or what?

May 25, 2015
Medical Student
I have a confusion on translocation. My question is, For eg, if there is t(A,B) ,does this mean-
1. gene on chr. A translocates to gene on chr B? ,or,
2. gene on chr B translocates to gene on chr A?

I came across the following translocations when I was reading WBC disorders which really made me confused

1. In acute promyelocytic leukemia , there is t ( 15,17) which involves translocation of the retinoic acid receptor (RAR) on chr. 17 to chr.15
2.In follicular lymphoma, t (14,18) occurs in which Bcl 2 on chr. 18 translocates to the Ig heavy chain locus on chr. 14
3.. In mantle cell lymphoma t(11,14) takes place in which Cyclin D1 gene on chromosome 11 translocates to Ig heavy chain locus on chr. 14.

Can anyone pls help me out to dispel this confusion.Thanks.


Happy on 5-HT
10+ Year Member
Aug 13, 2008
Resident [Any Field]
Hey the numbers of the chromosomes are simply listed in numerical order;,

a notation of t(A,B) simply denotes a joining of gene elements, not necessarily a "direction". For example t(14,18) implies a joining of IgH element with BCL2 gene. Or the case of BCR-ABL : t(9,22) which can have p190 or p210 fusion proteins (different possible gene variants)

The usual paradigm is that a translocation can occur in multiple ways, with the same result.
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