Question

1. Pribnow box - what would RNA look like after a mutation and why?

2. -35 region of DNA what would be a co sequence of mutations, is it universal or gene specific, what would the RNA look like and why?

3. beta subunit region of DNA what would be a consequence of mutations , is it universal or gene specific, what would the RNA look like and why?

Answer 1

1. The Pribnow box/TATA box/Hogness box/-10 sequence is a consensus sequence of 5'-TATAAT-3' which is a highly conserved DNA sequence near the 3' end of specific homeotic genes. It encodes a DNA-binding domain that allows the homeobox proteins to bind to and regulate gene expression in development. They are sequences within the prokaryotic promoter region that are recognized by the RNA polymerase holoenzyme. The site of this box is about 25-30 base pairs upstream of the initial point of transcription and mutations in this sequence results in the reduction of transcription as it loosed the ability to bind to transcription factors. This region is essential for DNA unwinding.

2. The -35 sequence TTGACA is a sequence within the prokaryotic promoter region that are recognized by the RNA polymerase holoenzyme. Mutations in this sequence affects the transcription of the gene controlled by a mutant promoter. The sigma subunit of RNA polymerase binds at this site. It is universal.

3. The beta subunit of the DNA polymerase holoenzyme forms the pre-initiation complex during prokaryotic DNA replication. The gamma complex of DNA polymerase III, catalyzes ATP to chaperone two beta subunits to bind to DNA. Once bound to DNA, the beta subunits can freely slide along double stranded DNA binding the alpha-epsilon complex and initiate DNA replication. Mutation in the beta subunit of the DNA polymerase impairs DNA transcription.