Final answer:
The statement is generally true; mutations in the promoter sequences can impair the binding of transcription factors and RNA polymerase, often resulting in decreased transcription or a complete failure to express the associated gene.
Step-by-step explanation:
If promoter consensus sequences are mutated, the gene will probably not be expressed. This statement is generally true. Promoter regions contain specific sequences such as the TATA box, which are crucial for the binding of transcription factors and RNA polymerase—those proteins responsible for initiating transcription of DNA into RNA. Mutations in these sequences can alter the binding site, either decreasing or increasing the rate of transcription, but more commonly resulting in a deceased rate or complete failure to transcribe the adjacent gene into mRNA.
Mutations in the promoter sequence often lead to a failure of RNA polymerase to attach to the DNA strand, hence preventing the transcription process from beginning. Since transcription is the first step in gene expression, any change in the promoter sequence that impedes RNA polymerase binding can lead to the gene not being expressed at all.