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The DNA-binding domain of the Lac repressor protein has a characteristic three-dimensional structure known as the:

a) Helix-turn-helix motif
b) Zinc finger domain
c) Leucine zipper motif
d) Homeodomain

User Badashi
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Final answer:

The Lac repressor protein's DNA-binding domain is characterized by the helix-turn-helix motif, which allows for specific DNA interactions to regulate gene expression.

Step-by-step explanation:

The DNA-binding domain of the Lac repressor protein has a characteristic three-dimensional structure known as the helix-turn-helix motif. In the context of gene regulation, particularly the regulation of the lac operon, the Lac repressor protein can bind to operator DNA sequences to prevent transcription. The helix-turn-helix motif of the protein enables it to recognize and bind specific sequences of DNA by fitting into the major groove of the DNA double helix.

Other DNA-binding motifs and domains commonly found in regulatory proteins include the zinc finger domain and the leucine zipper motif, as well as the homeodomain, each with a distinct structure allowing for specific interactions with DNA to regulate gene expression.

User Kim Stacks
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