Low levels of gene expression can be detected by:a. Northern blot
Reverse transcriptase-polymerase chain reaction (RT-PCR). RT-PCR is capable of finding a single copy of RNA. Northern blot analysis requires at least 5 to 10 μg of total RNA. Western blot analysis is for determining protein levels. Southern blot analysis is for genotyping and requires multiple copies of DNA. Gene transfer is not a detection method.