Download BSC 219

BSC 219
Homework 6
Due 10/18/12
1) ( 3 points) Describe the main ways that eukaryotic transcription initiation is
different from prokaryotic transcription initiation.
Eukaryotic initiation involves a large number of proteins to form an
initiation complex that recruits RNA Polymerase to the promoter region.
The DNA sequences and some proteins in the complex are variable
between promoters. Prokaryotic initiation relies only upon the relative
strength of the promoter sequences at recruiting Sigma factor and RNA
Polymerase to the promoter.
2) (2 point) Two sequences of a prokaryotic promoter are shown below.
Sequence 1 is the wild-type sequence, and sequence 2 is a mutant sequence
(mutation shown in bold) that results in increased transcription of the gene.
Explain why sequence 2 shows this phenotype.
Sequence 1
–10
...CGAATAATGAA...
Sequence 2
–10
...CGTATAATGAA...
The mutation caused an increase in transcription because it resulted in a 10 sequence that now has the strongest possible sequence for recruiting
sigma factor and RNA Polymerase (TATAAT). This would result in an
increase in initiation and a resultant increase in transcription of the gene.