Final answer:
An abnormal eukaryotic cell line with longer mRNAs than normal cells could be caused by a mutation in the RNA polymerase gene. Abnormal proteins in these cells being longer or shorter could be due to mutations in the genes encoding those proteins.
Step-by-step explanation:
The reason for an abnormal eukaryotic cell line making longer mRNAs than normal cells could be a mutation in the RNA polymerase gene. This mutation would cause the mRNA molecules to have more nucleotides than usual.
Intriguingly, the abnormal proteins in these cells being either longer or shorter than normal could be due to mutations in the genes encoding those proteins. These mutations could result in abnormal amino acid sequences, leading to the production of longer or shorter proteins.