When the cell is NOT in the presence of tryptophan,

A. RNA polymerase can transcribe mRNA.
B. the repressor proteins bind to the operator.
C. structural genes are not transcribed.
D. the repressor proteins are active.

Acquired mutations can result from radiation pollution toxins inheritence select all that apply

Several bird species feed in a certain species of tree. each bird species feeds in a different part of the tree. which statement is true of these bird species? a. they have adapted to different niches due to competition b. they have a carnivorous relationship with the tree species. c. they have adapted to different niches due to predation d. they have a symbiotic relationship with the tree species.

The carbon cycle is best defined as a process in which a. carbon changes from inorganic forms to organic forms and back b. carbon is changed into other elements such as oxygen or nitrogen c. carbon is continually created from the sun’s energy by plants d. carbon is consumed and regenerated from other elements such as oxygen and nitrogen