With regard to translation in prokaryotes,the gene products are often encoded on polycistronic mRNAs.As a result,the quantities of each of the proteins are often graded,such that the first gene has a great deal of protein translated,whereas the last gene has very little.Which of the following features of prokaryotic translation may account for increased production of some products and decreased production of others?
A)The different messages have sequences with more or less homology to the ShineDelgarno sequence; fewer ribosomes binding results in less product.
B)Feedback regulation of ribosomes tells the cell that enough product is made, and ribosomes from such mRNAs dissociate.
C)Because transcription and translation in prokaryotes are essentially coupled, there is no gradation in the amount of individual proteins made from a polycistronic message.
D)There is no termination sequence at the end of each gene, so one long protein is made, resulting in equal amounts of products.
E)all of the above

Question

Quizplus · Accepted Answer

The different messages have sequences with more or less homology to the Shine-Dalgarno sequence. This sequence is recognized by the ribosome and allows for binding and initiation of translation. If the Shine-Dalgarno sequence is less homologous, fewer ribosomes will bind and result in less protein production. This explains why the quantities of each protein can vary in polycistronic messages. Feedback regulation (B) and coupling of transcription and translation (C) are not directly related to the graded production of proteins in polycistronic messages. There is typically a termination sequence at the end of each gene (D) which allows for separate translation of each protein.

With Regard to Translation in Prokaryotes,the Gene Products Are Often