In an effort to identify regulatory sequences important for transcription, a collection of mutants has been generated. Each mutant carries a single base mutation in a region of DNA 400 bp immediately upstream of gene Y, such that, collectively, the full mutant collection contains a mutation at each nucleotide position in the 400 bp region. Transcription of gene Y is measured in each mutant relative to wild type, and the cumulative results are as follows. “-1” indicates the nucleotide one base upstream of the transcriptional start site.

Coordinates Transcription level relative to wild type

Mutations in bp -1 to -30 1.0 (on average) no fx

Mutations in bp -31 to -40 0.3 (on average) activator

Mutations in bp -41 to -150 1.0 (on average) no fx

Mutations in bp -151 to -158 3.0 (on average) repressor

Mutations in bp -159 to -200 1.0 (on average) no fx

Mutations in bp -201 to -220 0.3 (on average) activator

Mutations in bp -221 to -400 1.0 (on average) no fx

From these data, which of the following statements accurately identify regions that are required for likely recognition by transcriptional activators or repressors?

A) The -31 to -40 and -201 to -220 DNA sequences are required for binding of a transcriptional activator; the -151 to -158 sequence is required for binding of a transcriptional repressor.

B) The -31 to -40 and -201 to -220 DNA sequences are required for binding of a transcriptional repressor; the -151 to -158 sequence is required for binding of a transcriptional activator.

C) The -1 to -30, -41 to -150, -151 to -158, -159 to -200, and -221 to -400 DNA sequences bind transcriptional activators.

D) The -31 to -40 and -201 to -220 DNA sequences bind transcriptional repressors.

E) C and D are correct

Answer rating: 100% (QA)

When a mutation in regulatory region of a gene results in increased transcription compared to wild t... View the full answer