A bacterium can make the amino acid glycine or absorb it from its surroundings. A biochemist finds that glycine binds to a repressor protein and causes the repressor to bind to the bacterial chromosome, turning off an operon. If it is like other similar operons, the presence of glycine will result in the __________.

• A. inhibition of bacterial cell division
• B. breakdown of glycine
• C. formation of sex pili
• D. production of the repressor protein
• E. cessation of the synthesis of glycine

Answer: (E)

Verified step by step guidance

1. Understand the role of operons in bacterial gene regulation. Operons are clusters of genes under the control of a single promoter and are regulated by repressor proteins.
2. Recognize that the presence of glycine acts as a corepressor. When glycine binds to the repressor protein, it activates the repressor, allowing it to bind to the operator region of the operon.
3. Consider the effect of the repressor binding to the operon. This binding prevents RNA polymerase from transcribing the genes in the operon, effectively turning off the operon.
4. Identify the function of the operon in question. Since glycine binding turns off the operon, the operon is likely responsible for the synthesis of glycine.
5. Conclude that the presence of glycine leads to the cessation of the synthesis of glycine, as the operon responsible for its synthesis is turned off by the repressor-glycine complex.