Final answer:
Introns are not deleted before transcription; they are transcribed into pre-mRNA and later removed during RNA splicing to create mature mRNA.
Step-by-step explanation:
The statement that introns are deleted before a gene is transcribed from DNA into mRNA is false. Introns are indeed transcribed into pre-mRNA along with exons. After transcription, the pre-mRNA undergoes a process called splicing, where introns are removed and exons are joined together to form the mature mRNA that leaves the nucleus for translation. This splicing is conducted by a complex mechanism involving the spliceosome, ensuring that introns are accurately and precisely removed. If even a single nucleotide is out of place after splicing, the resulting protein could be dysfunctional.