[Campbell Biology P.902] Which statement accurately differentiates between ein and ctr mutan... | Practice Question

Which statement accurately differentiates between ein and ctr mutants in Arabidopsis regarding the ethylene triple response?

  • A: *ein* mutants fail to undergo the triple response due to a lack of ethylene production, while *ctr* mutants undergo it even without ethylene due to activated signaling.
  • B: *ein* mutants are insensitive to ethylene because they lack a functional receptor, whereas *ctr* mutants show a constitutive triple response because their signaling pathway is permanently on.
  • C: Both *ein* and *ctr* mutants exhibit the triple response constitutively, but *ein* mutants can be restored to wild-type phenotype with ethylene synthesis inhibitors.
  • D: *ein* mutants show increased stem elongation, while *ctr* mutants show reduced stem elongation, indicating opposite effects on growth.

Explanation

The text states that ein mutants are 'ethylene-insensitive ein mutants, which fail to undergo the triple response after exposure to ethylene' and that 'Some types of ein mutants are insensitive to ethylene because they lack a functional ethylene receptor.' In contrast, ctr mutants are described as 'constitutive triple-response ctr mutants, undergo the triple response in air but do not respond to inhibitors of ethylene synthesis' and that 'ethylene signal transduction is permanently turned on, even though ethylene is not present.' This clearly differentiates their underlying defects and resulting phenotypes.