Question

Please explain your answers as best as you can. I want to be able to understand.

The first drawing below represents the transcription start site and upstream region of a eukaryotic gene. In addition, four deletion constructs are shown, where the unboxed area represents a deletion of upstream DNA. Note the location of the +1 start site and the promoter, which includes the TATA box Non-deleted DNA template and DNA of the various deletions constructs were added to both systems and transcription efficiency was evaluated. This experiment sets out to identify effects of deletion of promoter and potential regulatory sites. The results of the experiment are shown in the table. +++ high efficiency transcription; + low efficiency transcription; 0 no transcription 1. Why do we see no expression from the -11 deletion, in either treatment? 2. Between which nucleotide positions could an enhancer lie? 3. Explain the difference in expression between the two systems when there is undeleted DNA added. 4. Explain why, with nuclear extract, expression is significantly reduced once the -150 deletion is added. 5. Why are expression levels the same between the two systems when the -150 deletion is added?

Answer 1

1. the deletion is in the promoter region that is why the transcription does not take place

2. -250 to -150 region because its deletion reduces the expression when deletion happened in the particular region.

3. the purified system lacks the enhancer binding protein that is why even the undeleted DNA is added but th eexpression is less as compared to the nuclear extract where as in the nuclear extract all the component for the transcription including the enchancer binding protein is available for the better expression.

4.  -250 to -150 region because its deletion reduces the expression when deletion happened in the particular region and the -150 deletion correspond to the enhancer region.

5. since -150 region is a enhancer and the purified system does not have enhancer binding protein and its level of transcription is similar to the level of transcription of the -150 deletion as it correspond to the enhancer region. in both the cases the enhancer element is non functional