Answer to Question #189961 in Molecular Biology for Muhammad Abdul Sam

Question

Suppose we have a consensus sequence “5′-GTAATC-3′” at a particular site in the genome of a specie. Does this mean that all members of that specie will have the sequence “5′-GTAATC-3′” at that particular site? If yes, explain. If no, why?

Answer 1

In terms of a nucleotide sequence, a consensus sequence is a sequence of nucleotides that is similar or identical between regions of homology in different but related DNA sequence.

One example of consensus sequence in prokaryotic genome is Pribnow box which is a short sequence element present in the promoter at -10 and has the consensus sequence of six nucleotides 5'-TATAAT-3'.

Function: The Pribnow box is a part of the promoter site and plays a critical role in DNA transcription in bacteria as it is recognized and bound by RNA polymerase subunit.

b) Determine the consensus sequence of the following six promoter sequences:

Based on alignment of these six sequences as shown below the consensus sequence is : GGCATTGTCA

1 GGCATTGACT

2 GCCATTGTCA

3 CGCATAGTCA

4​GGAAATGGGA

5 ​GGCTTTGTCA

6 GGCATAGTCA

C) Mutation at which of the 10 positions would most likely affect promoter function? Why?

A mutation that causes the promoter to deviate from the consensus sequence would most likely affect the promoter function. From the given six sequences the positions that is most conserved is position 7 (G) and seems critical for promoter function, so any mutation in this position may adversly affect the promoter function.