Quiz 15: Controls Over Genes


Yes, all the transcriptional controls perform similarly with same steps of mechanism in both eukaryotes and prokaryotes but they both differ with the presence of few controlling elements. This is because of distinct behaviour shown by each element with due respect to the nature of both organisms. Both the mechanisms (basic steps) are summarised below: Eukaryotic transcriptional control- it includes: 1. Enzymatic synthesis of RNA - that requires • RNA polymerase I • RNA polymerase II • RNA polymerase III 2. Binding to promoters, enhancers and silencers 3. Initiation 4. Elongation and 5. Termination Prokaryotic transcriptional control- it includes: 1. Enzymatic synthesis of RNA - that requires • RNA polymerase enzymes 2. Binding of RNA polymerase to promoter sites (DNA molecule) 3. Initiation 4. Elongation 5. termination

The expression of genes refers to the overall process of selectively reading and using genetic information lying within the cells. The gene produces a character irrespective of the other genes present in the organism as well as the environment to which the organism is exposed. However, the expression of gene is affected in various ways by other genes of the organism. It includes all random changes occurring within the cells in response to various chemical conditions, internal and external environmental signals. In this way, cells produce a particular mRNA only when the encoded protein is required. Therefore, all the given options in the question are correct. Hence, the correct option is d. All of the above.

This answer would be based on pure assumptions. It is almost senseless that all cells would inherit the same genetic information in order to encode proteins. If all cells inherit same information, that means they share same gene expression, resulting in no specific cell differentiation. Cell differentiation is resulted through sudden changes occurring within gene expression. In this case, it would be most difficult task to distinguish between different types of cells. It is the protein that functions in characterising and structuring various different types of cells in our body whether they are blood cells (RBC, WBCs), liver cells, muscle cells or nerve cells etc. Therefore, RBC and WBC differences are been caused by the changes occurring in the gene expression. On the other hand, nerve cell and WBC can be differentiated by means of their genetic content or special functions shared between both within a genome.

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