Question

Cell differentiation always involves

(A) transcription of the myoD gene.

(B) the movement of cells.

(C) the production of tissue-specific factors

(D) the selection loss of certain genes from the genome.

Short answer

(A) The statement “the amino acid inactivates the repressor” is false.

(B) The statement “the repressor is active in the absence of the amino acids” is false.

(C) The statement “the amino acid is a corepressor” is true.

(D) The statement “the amino acid turn on transcription of the operon” is false.

Step-by-step solution

Operon

The functional unit present in the DNA is the operon. The operon system is a cluster of genes present in the prokaryotes. It controls the expression of proteins from the genes present in the operon.

Explanation of option “(A)”

A repressor is a molecule that can bind to the operator region and block the production of protein. Amino acids are the products produced from the enzyme, which do not involve indirect inhibition.

Thus, the amino acids are not the repressor since the regulation mechanism is similar to the trp operon.

Therefore, the given statement is false.

Explanation of option “(B)”

The production of amino acids can regulate this metabolism. When the amino acids are synthesized, the repressor molecules get activated to control the activity of the amino acid production.

Thus, the absence of amino acid does not lead to the activation of the repressor.

Therefore, the given statement is false.

Explanation of option “(C)”

Corepressor is the molecule that is not involved in the direct inhibition of the trp operon. Instead, the amino acid produced binds to the repressor. It, in turn, regulates the trp operon.

Thus, the amino acid metabolism is similar to trp operon. The amino acid acts as a corepressor to regulate this mechanism.

Therefore, the given statement is true.

Explanation of option “(D)” 

The amino acid regulation mechanism does not activate the transcription. It involves the control of the transcription process that produces a particular protein.

Thus, the amino acids turn off the transcription of the operon.

Therefore, the given statement is false.