Due to a mutation in the HEXA gene, a substance called GM2, normally present in the tissues and nerve cells of the brain, accumulates there. This mutation mainly effects enzymes associated with which organelle in an affected individual's cells?

Lysosomes.

Explanation:

HEXA (Hexosaminidase A) is the functional enzyme and encoded by the HEXA gene. The main function of this enzyme is the hydroxylation of the gangliosides.

The mutation in this gene leads to the lysosomal storage disease. The GM2 starts accumulating in the lysosomes and causes Tay Sach's disease. This is a genetic disorder that leads to the breakdown of the cells of the spinal cord and the brain.

Thus, the answer is lysosomes.

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