A friend of yours isolated the coding sequence for pretendin from sick individua
ID: 252914 • Letter: A
Question
A friend of yours isolated the coding sequence for pretendin from sick individuals. Now you are trying to express large amounts of the mutated pretendin in bacteria, so that you may be able to purify the mutant protein and run a series of biochemical tests on it, trying to figure out what's wrong with it. However, you encounter a problem... Even though you were able to confirm that the DNA for pretendin has been successfully incorporated into the bacterium, no protein is being produced!! You check the sequence of the DNA that went into the bacterium, and you notice that it has everything in needs to be expressed in eukaryotic cells Taking into account what you know about differences in expression between eukaryotes and prokaryotes, what may have gone wrong...?Explanation / Answer
Most of the eukaryotes contain split genes i.e. genes sequences contain coding sequences interrupted by non-coding sequences.
Coding sequences of a gene = Exons
Non-coding sequences of a gene = Introns
Introns are present in the hnRNA that is synthesized in the nucleus by RNA polymerase. The introns from the hnRNA must be removed before the RNA is to be translated. The process of removing introns and joining exons together is known as splicing.
In the given case, introns might be present in the given eukaryotic gene. Hence the protein product is not synthesized in the prokaryotic cell as they lack splicing machinery to remove introns.
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