Explain or Teach these Concepts to a Friend

• Describe the circuitry that allows some B. subtilis cells to be ComK-ON and others to be ComK-OFF. You should use the words “positive feedback loop”, “threshold”, “noise”, and “cooperativity” in your explanation.
• Explain why it may be advantageous for a bacterial population to harbor two or more subpopulations with different cell fates/characteristics. Are there disadvantages to this strategy?
• Explain why the precise levels of expression of the same genes varies from cell to cell in an otherwise homogeneous population of cells. Describe two possible sources of noise in gene expression.
• The fly is said to have a compound eye. Why? Are color receptor genes expressed in a uniform pattern across the fly retina? Explain.

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