If only 1 in 1,000 cells were transformed, what does this imply about the number of cells in a 50 picoliter suspension?

If only 1 in 1,000 cells were transformed, what does this imply about the number of cells in a 50 picoliter suspension?

• A. There must be thousands of cells in 50 pL.
• B. There are only a few cells.
• C. The cells are extremely large.
• D. The transformation occurs at 100% efficiency.

Answer: (A)

The idea is that transforming only 1 in 1,000 cells means the chance of any single cell transforming is 0.001. In a sample, the expected number of transformed cells equals the total number of cells divided by 1,000. For a 50 pL suspension to yield about one transformed cell on average, it needs roughly 1,000 cells in that tiny volume. That’s why a suspension of 50 pL is interpreted as containing thousands of cells. If there were only a few cells, you’d expect far fewer than one transformation on average, and the statement about 1 in 1,000 would not be supported. The idea that transformation occurs at 100% efficiency would contradict the given 1 in 1,000 rate.

The idea is that transforming only 1 in 1,000 cells means the chance of any single cell transforming is 0.001. In a sample, the expected number of transformed cells equals the total number of cells divided by 1,000. For a 50 pL suspension to yield about one transformed cell on average, it needs roughly 1,000 cells in that tiny volume. That’s why a suspension of 50 pL is interpreted as containing thousands of cells. If there were only a few cells, you’d expect far fewer than one transformation on average, and the statement about 1 in 1,000 would not be supported. The idea that transformation occurs at 100% efficiency would contradict the given 1 in 1,000 rate.