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Gene Expression. In studies of the human genome, gene expression levels are ofte

ID: 3203198 • Letter: G

Question

Gene Expression. In studies of the human genome, gene expression levels are often studied to investigate patterns that might identify certain diseases. Consider three different genes A, B, and C that have the potential to cause cancer (called oncogenes). In a sample of cancer patients it was found that:

60% have high expression of gene A, 40% have high expression of gene B, and 25% have high expression of gene C

70% have high expression of A or B (or both), 69% have high expression of A or C (or both), and 52% have high expression of both B or C (or both)

8% have high expression of all three genes

Find the probability that a randomly selected cancer patient.

a. Has high expression in both genes A and B.

b. Has high expression in both genes A and B, but not C.

c. Has high expression in at most two genes.

Explanation / Answer

a. P(A)-P(B)-P(AuB)=0.60+0.40-0.70=0.3

b.a-P(C)=0.3-0.25=0.05

c. we will first find P(AnC) and P(BnC)

P(AnC)=P(A)+P(C)-P(AuC)=0.6+0.25-0.69=0.16

P(BnC)=P(B)+P(C)-P(BuC)=0.4+0.25-0.52=0.13

required probability =0.3+0.16+0.13=0.59