A cell has five molecules of a rare mRNA. Each cell contains 4 × 10⁵ mRNA molecules. How many clones one will need to screen to have 99% probability of finding at least one recombinant cDNA of the rare mRNA, after making cDNA library from such cell? (A) 4.50 × 10⁵ (B) 3.50 × 10⁵ (C) 4.20 × 10⁵ (D) 4.05 × 10⁵
A cell has five molecules of a rare mRNA. Each cell contains 4 × 10⁵ mRNA molecules. How many clones one will need to screen to have 99% probability of finding at least one recombinant cDNA of the rare mRNA, after making cDNA library from such cell?
(A) 4.50 × 10⁵
(B) 3.50 × 10⁵
(C) 4.20 × 10⁵
(D) 4.05 × 10⁵
Answer
Answer: (A) 4.50 × 10⁵
To have a 99% probability of finding at least one clone, one must consider the probability of not finding the clone and adjust accordingly. For a rare mRNA with 5 molecules per cell and assuming the probability of finding a clone in one screening attempt, approximately 4.50 × 10⁵ clones are needed to achieve this probability.