[Campbell Biology P.441] In the "Normal Breast Cells in a Milk Duct" diagram, what does the ... | Practice Question

In the "Normal Breast Cells in a Milk Duct" diagram, what does the "+" symbol next to ERα, PR, and HER2 indicate regarding their levels in normal breast cells?

  • A: They are currently active and binding ligands.
  • B: They are present at normal levels.
  • C: They are overexpressed and contributing to cancer.
  • D: They are absent or have very low expression.
  • E: They are present at normal levels.

Explanation

The section 'Normal Breast Cells in a Milk Duct' explicitly states: 'In a normal breast cell, the three signal receptors are at normal levels indicated by + : ERα+, PR+, HER2+'. The '+' symbol directly refers to 'normal levels'.