In humans a genetic syndrome called holoprosencephaly result

In humans, a genetic syndrome called \"holoprosencephaly\" results in a fusion of the anterior brain regions, essentially producing cyclopia (a single eye). Scientists investigated mutations in a gene called Sonic Hedgehog, previously shown to be involved in brain development. In holoprosencephalic patients, they found normal sized Shh mRNA, normal Shh protein, but reduced amounts of both. Based on these findings, what possible mutation(s) could have caused the phenotype? Select all the correct answers. a stop codon mutation in the second Shh exon a mutation in a large intron that contains a regulatory element a missense mutation in a Shh exon a frameshift mutation in a Shh oxon a mutation in an enhancer element 470 bp upstream of the transcription start site of Shh Which of the following is the most likely effect of a mutation in the 3\'UTR? the protein made from the mRNA may not fold properly the stability of the mRNA changes the mRNA is transcribed in the wrong cell type a problem with mRNA splicing the mRNA is not transcribed

Solution

ANSWER TO PART A

Mutation in the enhancer element 470 bp upstream of TSS........... Since enhancers increase the transcript expression levels in position and direction independant manner ... enhancers bind transcriptional factors via mediator complex by dna looping and hence increase transcript levels ... in the disease case question states that mrna levels decrease so enhancer would be the most appropriate answer

PART B

okay the answer would be that the stability of the mRNA changes.... THOUGH THERE ARE OTHER EFFECTS ALSO but stability effect by 3\'UTR is most prominent

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