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Simple question about deleted genes in TCGA CNV level 3 data

Hi everyone,

I have a simple question about aCGH data: if you have two copies per gene and your log2 ratio is cancer/normal, how can you observe log2 = -4? That means 1/16... 16 original copies? I understand log2 = -1 (1/2).

Thank you!

log cnv r

1 answer

this is cancer, you measure a copy-number of a mixture of cells. if your tumor has a homozygous deletion, but 1/16of the sequenced cells are normal and diploid, you get 1/16 ratio.

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