Genetic testing revealed these two mutations (hypothetically):

IVS11+6G>A and IVS11-4G>A

Could you please explain every part of this notation, especially "+" and "-" signs.

up vote 1 down vote accepted

These describe mutations (SNPs) in introns.

IVS stands for intervening sequence (which is another term for intron).

The number following IVS specifies which intron the mutation occurs in (intron 1 follows exon 1, etc).

The +n or -n, where n is an integer, gives the location of the nucleotide. +n counts 3' from the preceding exon whereas -n counts 5' from the following exon. I think that the first and last nucleotide of each exon is given position 0 such that, for example, +1 refers to the first nucleotide of the intron and -1 refers to the last.

X>Y, where X and Y are nucleotides, describe what mutation has occurred.


IVS11+6G>A means a G to A transition at position +6 of intron 11

IVS11-4G>A means a G to A transition at position -4 of intron 11

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