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MCB4403 Ch. 10 Homework Questions and
Answers (Expert Solutions)
Q: In E. coli, eight enzymatic steps are involved in the biosynthesis of arginine from
glutamate. The synthesis of the required enzymes is subject to control by the ArgD
protein, which, on its own, binds weakly to a regulatory sequence just downstream of the
promoter regions for these genes. Upon the addition of excess arginine to the growth
medium, the respective mRNA molecules are no longer produced. What is the likely role
of arginine in the control of these genes?
ANS 🗹🗹: corepressor
Q: Genes for which of the following functions would be constitutively expressed in a
bacterial cell such as E. coli?
ANS 🗹🗹: DNA replication
Q: Which of the following are features of operons? Select all that apply.
ANS 🗹🗹: operator, promoter, protein-coding genes
Q: What is the role of the first structural gene (lacZ) in the lac operon? Select all that
apply.
ANS 🗹🗹: it isomerizes lactose into allolactose, it breaks down lactose into glucose
and galactose
Q: Increased synthesis of _____ is a direct result of decreasing glucose levels.
ANS 🗹🗹: cAMP
Q: Which of the following elements must be present for attenuation of the trp operon to
occur? Select all that apply.
ANS 🗹🗹: charged tRNA Trp, RNA polymerase, ribosomes
Q: When intracellular levels of tryptophan are low, the _________ stem loop forms,
which results in ___________ of transcription.
MCB4403 Ch. 10 Homework Questions and
Answers (Expert Solutions)
Q: In E. coli, eight enzymatic steps are involved in the biosynthesis of arginine from
glutamate. The synthesis of the required enzymes is subject to control by the ArgD
protein, which, on its own, binds weakly to a regulatory sequence just downstream of the
promoter regions for these genes. Upon the addition of excess arginine to the growth
medium, the respective mRNA molecules are no longer produced. What is the likely role
of arginine in the control of these genes?
ANS 🗹🗹: corepressor
Q: Genes for which of the following functions would be constitutively expressed in a
bacterial cell such as E. coli?
ANS 🗹🗹: DNA replication
Q: Which of the following are features of operons? Select all that apply.
ANS 🗹🗹: operator, promoter, protein-coding genes
Q: What is the role of the first structural gene (lacZ) in the lac operon? Select all that
apply.
ANS 🗹🗹: it isomerizes lactose into allolactose, it breaks down lactose into glucose
and galactose
Q: Increased synthesis of _____ is a direct result of decreasing glucose levels.
ANS 🗹🗹: cAMP
Q: Which of the following elements must be present for attenuation of the trp operon to
occur? Select all that apply.
ANS 🗹🗹: charged tRNA Trp, RNA polymerase, ribosomes
Q: When intracellular levels of tryptophan are low, the _________ stem loop forms,
which results in ___________ of transcription.
