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A scientist was studying an in vitro eu...

A scientist was studying an in vitro euckaryotic transcription system, which produced both capped and uncapped mRNAs. For an experiment, he incubated these mRNAs with mammalian cell nuclear extract and quantified the different products as shown . Which of the following graphs represents the expected result correctly ?

A

B

C

D

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The correct Answer is:
To solve the question regarding the expected results of an in vitro eukaryotic transcription system that produces both capped and uncapped mRNAs, we will analyze the processes involved in mRNA processing and how they relate to the graphs provided. ### Step-by-Step Solution: 1. **Understanding Pre-mRNA**: - Eukaryotic transcripts initially exist as pre-mRNA, which contains both introns and exons. This form is not yet functional and is the starting point for further processing. 2. **Splicing Process**: - The first step in mRNA processing is splicing, where introns are removed, and exons are joined together. This results in spliced mRNA, which is a more stable and functional form of mRNA. 3. **Capping and Polyadenylation**: - After splicing, the next step is capping, where a 7-methylguanylate cap is added to the 5' end of the mRNA. This cap protects the mRNA from degradation and assists in ribosome binding during translation. - Additionally, a polyadenylate (poly-A) tail is added to the 3' end of the mRNA. This tail also contributes to the stability of the mRNA and aids in the export of mRNA from the nucleus to the cytoplasm. 4. **Quantification of mRNA Forms**: - After processing, we can expect to quantify three forms of mRNA: - **Pre-mRNA**: This will be the least abundant since it is the starting material and is rapidly processed. - **Spliced mRNA**: This will be more abundant than pre-mRNA but less than polyadenylated mRNA. - **Polyadenylated mRNA**: This will be the most abundant form, as it represents the final processed and stable mRNA ready for translation. 5. **Analyzing the Graphs**: - When analyzing the graphs, we should look for a representation where: - The quantity of pre-mRNA is the lowest. - The quantity of spliced mRNA is intermediate. - The quantity of polyadenylated mRNA is the highest. - The graph that meets these criteria will represent the expected results correctly. 6. **Conclusion**: - Based on the analysis, the correct graph will show the highest quantity of polyadenylated mRNA, followed by spliced mRNA, and the lowest for pre-mRNA. This corresponds to option D, which accurately reflects the expected results of the experiment.
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