Q4 - Stochastic Noise in a Dual-Reporter Plasmid

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

A plasmid was inserted into bacteria (1). Red fluorescent protein (RFP) or green fluorescent protein (GFP) are produced from the genes in this plasmid whenever transcription factors bind to their promoters. The red and green gene promoter sequences are identical. Plasmid DNA replication starts at the origin of replication, and replication forks move outwards in both directions at the same speed. Replication occurs whenever replication factors bind to the origin of replication. The red and green fluorescence intensity of individual bacteria was measured (2).

Figure for Q4: Stochastic Noise in a Dual-Reporter Plasmid

Using the information and data, determine which of the statements are true or which are false.

A. Replicating plasmids have unequal numbers of red fluorescent protein and green fluorescent protein genes.

B. On average, cells in Region A contain more replication factors than those in Region B.

C. On average, cells in Region A contain more transcription factors than those in Region B.

D. Increasing the activity of transcription factors is expected to increase the number of cells containing equal amounts of green fluorescent protein and red fluorescent protein.

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Question reproduced from IBO 2017, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Official answer key & worked solutions