Question

2.) Consider the following RNA sequence, which represents the beginning of an open reading frame: 5’-AUGGGACUAGAUACC-3’. Examine each of the sequences below, describe the change to the sequence, and state whether it represents a silent, missense, nonsense, or frameshift mutation. If frameshift, be sure to include the consequences of the frameshift (nonsense or massive missense). Use the codon table. a) 5’-AUGGGUCUAGAUACC-3’ b) 5’-AUGCGACUAGAUACC-3’ c) 5’-AUGGGACUAGUUACC-3’ d) 5’AUGGGACUAAGAUACC-3’ 3. Using a couple of sentences each, describe the function of each of the following in regulating eukaryotic gene expression: a) promoter b) enhancer c) histone acetyltransferase d) 5-methylcytosine

Answer 1

original sequence:

AUGGGACUAGAUACC

a) AUGGGUCUAGAUACC: silent mutation since 6th nucleotide has undergone poin mutation, it has changed from GGA to GGU, both codons code for glycine therefore it is a silent mutation

original sequence:

AUGGGACUAGAUACC

b) 5’-AUGCGACUAGAUACC-3: mis-sence mutation since the point mutation in this sequence changes the second amino acid from glycine to arginine (CGA)

AUGGGACUAGAUACC

c) 5' AUGGGACUAGUUACC: here, GAU has change to GUU; aspartate has changed to valine: mis-sense

AUG GGA CUA GAU ACC

d) d) 5’AUG GGA CUA AGA UAC C-3’

this is a frameshit mutation (massive mis-sense); the 4th and 5th codon change from asp and thr to arg and tyr respectively. As there was no stop codon involved this was not a non-sense mutation

a) Promoter: a promoter is a region located upstream to the transcription start site. this region binds the rna polymerase and helps to initiate the transcription of the particular gene

b) enhance: they are cis acting genetic elements located upstream to the promoter, these bind specific proteins called activators to enhance/increase the transciption level of the particular gene.

c) histone acytransferases: they are enzymes that transfer the acyl group to the tails of the histones to modify the chromatin wrapped around a gene. Addition of acyl groups increases the negative charge on histone and causes repulsion due to negative charge on DNA. This looses the chromatin around the gene and the gene is expressed.

d) 5-methylcytosine: it funtions as a marker in bacteria to protect the bacterial genome against its own restriction enzymes. in vertebrates its found in the CpG islands and regulate the gene expression.