1. In hippogriffs, the Talon gene, that is required for claws to form, is only e
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1. In hippogriffs, the Talon gene, that is required for claws to form, is only expressed in the toes of the animal In trying to understand how transcription is regulated in fantastic beasts, we have been analyzing the expression of the Talon gene. In the diagram below is the sequence of the Talon promoter, where the first nucleotide transcribed is an A, underlined in the sequence below. Two other sequences in this region are also underlined Below the sequence (labeled a-f) are diagrams representing the wild-type promoter (a), and several mutants that were tested for their ability to initiate transcription. Variants b through f either contain small deletions (b-d) or point mutations (e, f). At the right are indicated the relative levels of transcription for each variant, measured in arbitrary Units. 5AGAGCSCSCCATCATTAATGCGAGCTeGGGcTATAAGCTGATGCTGACGAGCTGATGTCATT... .3' Relative gene activity 10 Units 4 Units 2 Units o Units 20 Units 2 Units element might be affected, and explain why the a. For constructs b-f indicate: what promoter sequence expression level is changed to the extent shown.Explanation / Answer
From the above information it is clear that the sequence TATAAG upstream of the first nucleotide is more crucial for the gene activity as compared to the second underlined sequence GGGCGG.
We will expain the sequences and the resulting gene activities as follows:
For the wild type a sequence, both the underlined sequences are present and the gene activity is normal i.e 10 units.
For b, the second upstream sequence is deleted, but has the wild type first underlined sequence upstream of A. The gene acitivity is lower than wild type.This shows that the second sequence enhances the gene activity of the firrst sequence.
For c, the first sequence TATAAG is deleted while the second sequence remains unaltered. This drastically reduces the gene activity to 2 units showing the importance of first sequence.
For d , both the sequences are deleted which are crucial for gene activity. So as expected the gene activity will be zero.
For e, we see that the last nucleotide G of the first sequence undergoes point mutation to T which changes the sequence from TATAAG to TATAAT. The gene activity is doubled to 20 units as compared to wild type. This is the case of upmutation where sequence TATAAG undergoes point mutation so that it is changed to consensus sequence TATAAT leading to a strong promoter and thus increased gene activity.
For f, there is again a point mutation but the gene activity is reduced to 2 units. This is a case of down mutation in which strong promoters are changed to weak promoters which lead to decresed gene activity.
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