You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium. You have isolated a mutation that causes constitutive melibiase activity, which you designate MelA–. P1 phage mapping experiments using a Tn5 insertion linked to Mel1 show that MelA– is not linked to Mel1. Moreover you find that when an amber suppressor is introduced into a MelA– mutant, normal melibiase regulation is restored. Classify the MelA– mutation in terms of its basic genetic properties, 

#Question id: 4960

#SCPH06 I Botany

Letʹs say that a hypothetical submersible robot was used to collect samples of sedimentary rock from the sea floor along the section illustrated. The robot moved back and forth along the transect, collecting first from site A, then site III, then site B, then site II, and lastly site D. Assuming that sedimentation has occurred at a constant rate along the transect over the past million years, rearrange the sites mentioned above on the basis of the thickness of the sediments overlying the igneous rock, from thickest to thinnest.

#Question id: 4960

#SCPH28 | Zoology

Letʹs say that a hypothetical submersible robot was used to collect samples of sedimentary rock from the sea floor along the section illustrated. The robot moved back and forth along the transect, collecting first from site A, then site III, then site B, then site II, and lastly site D. Assuming that sedimentation has occurred at a constant rate along the transect over the past million years, rearrange the sites mentioned above on the basis of the thickness of the sediments overlying the igneous rock, from thickest to thinnest.

#Question id: 4961

#SCPH06 I Botany

An early consequence of the release of oxygen gas by plant and bacterial photosynthesis was to

#Question id: 4961

#SCPH28 | Zoology

An early consequence of the release of oxygen gas by plant and bacterial photosynthesis was to

#Question id: 4963

#SCPH06 I Botany

Which free-living cells were the earliest contributors to the formation of Earthʹs oxidizing atmosphere?

#Question id: 4963

#SCPH28 | Zoology

Which free-living cells were the earliest contributors to the formation of Earthʹs oxidizing atmosphere?