Iron is an essential nutrient that is acquired by organisms from the environment. When intracellular levels of iron are relatively high, living cells synthesize an iron-storage protein called ferritin.

The induction of ferritin synthesis by iron was investigated in rats. Figure 1 shows the results of an experiment in which cellular levels of ferritin protein were measured in the presence or absence of iron and actinomycin D, a drug that inhibits transcription.

Figure 2 shows the results of an experiment in which cellular levels of ferritin protein were measured in the presence or absence of iron and cycloheximide, a drug that inhibits translation.

Which of the following biotechnology approaches could be used to identify ferritin mRNA in a sample of total cellular RNA?

Question

Iron is an essential nutrient that is acquired by organisms from the environment. When intracellular levels of iron are relatively high, living cells synthesize an iron-storage protein called ferritin.

The induction of ferritin synthesis by iron was investigated in rats. Figure 1 shows the results of an experiment in which cellular levels of ferritin protein were measured in the presence or absence of iron and actinomycin D, a drug that inhibits transcription.

Figure 2 shows the results of an experiment in which cellular levels of ferritin protein were measured in the presence or absence of iron and cycloheximide, a drug that inhibits translation.

Which of the following biotechnology approaches could be used to identify ferritin mRNA in a sample of total cellular RNA?

BlackTom AI · Accepted Answer

To identify ferritin mRNA within total cellular RNA, we need an approach that detects a specific RNA sequence rather than protein or DNA. 
Option 1: 'RNA samples could be converted to protein and subsequently cut with a restriction endonuclease that recognizes DNA sequences.' This is conceptually flawed because RNA cannot be reliably converted to a single, meaningful protein product for restriction analysis, and restriction enzymes cut DNA, not RNA. Moreover, there is no standard method to identify ferritin mRNA by converting it to protein first. 
Option 2: 'RNA samples could be separated by size using agarose gel electrophoresis and incubated with labeled single-stranded DNA molecules that are complementary to the ferritin mRNA.' This is a classic description of a northern blot or a related hybridization assay. The RNA is separated by size, transferred, and probed with a labeled antisense DNA or RNA probe complementary to ferritin mRNA, enabling specific detection of the target mRNA. The use of a labeled complementary probe provides sequence-specific identification within a mixture of RNAs. 
Option 3: 'RNA samples could be examined under a high-power microscope to visually identify the ferritin mRNA.' mRNA are small molecules and cannot be visually identified by light or even high-powered microscopy without labeling; this approach lacks specificity and feasibility for detecting particular mRNA species in total RNA. 
Option 4: 'RNA samples could be directly cloned into a DNA plasmid, grown in bacteria, and tested for the ability to bind iron.' Cloning RNA into a plasmid and expressing in bacteria focuses on DNA or cDNA cloning and protein expression, not on identifying the presence or sequence of ferritin mRNA in a total RNA sample. Additionally, RNA does not directly convert to plasmids without an intermediate reverse transcription step, and binding to iron is not a relevant readout for mRNA identification. 
In summary, option 2 provides a sequence-specific RNA detection strategy suitable for identifying ferritin mRNA in total RNA by using a labeled complementary probe after size-based separation, whereas the other options rely on inappropriate or unsupported concepts for RNA identification in a mixed RNA sample.

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