Final answer:
A Northern Blot is used to observe mRNA expression levels by detecting the amount and size of mRNA molecules in a sample, whereas it does not measure protein concentrations, DNA replication rates, or ribosomal RNA structure.
Step-by-step explanation:
The student's question regarding the use of a Northern Blot to analyze equal total cellular RNA loaded into a gel addresses a specific technique within molecular biology. The characteristic that can be observed through this method is mRNA expression levels. Northern Blotting is a technique used to detect the amount and size of mRNA molecules in a sample, which are indicative of gene expression.
This technique is valuable because mRNA is the transcript of a gene that is ultimately translated into a protein, thus reflecting the activity of a gene. In contrast, the method does not provide information related to protein concentrations, DNA replication rates, or ribosomal RNA structure, as these are analyzed using other techniques such as Western blotting, DNA replication assays, and other forms of RNA analysis respectively.