11. How is the expression of genes controlled at the chromosomal level? a. DNA i
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11. How is the expression of genes controlled at the chromosomal level? a. DNA is spontaneously deleted from a chromosome if not needed b. DNA can be unwound into euchromatin to reduce the level of expression c. DNA can synthesize extra histones as needed d. DNA can either be condensed into heterochromatin or unwound into euchromatin The expression of DNA can only be controlled at the transcriptional level e. 12. Co-ordinated regulation of gene expression in bacteria is achieved by: Using the same transcriptional regulators to control expression of genes spread throughout the genome A single operon controlling the expression of genes required for a given process The presence of identical origins of replication in both plasmids and genomic DNA Polyadenylation of mRNAs Chemical modification of the histones associated with the bacterial DNA a. b. c. d. e.Explanation / Answer
11. Answer: d: DNA either condensed to form heterochromatin or unwind to form euchromatin.
In this way, the gene expression is controlled. The euchromatin region is not condensed so that it is easily identified by transcription missionary. But heterochromatin DNA is tightly coiled in such a way that transcription is not possible in these areas of DNA.
12) Answer: b: A single operon controlling gene expression of genes required for a given process.
According to operon concept, the genes coding for different enzymes which belongs to the same pathway are clustered together and all are controlled by the same regulatory mechanism and are called as operons. The regulatory mechanism may include promoter, operator and other regulator genes. The regulatory mechanisms decide the gene expression to proceed or to stop based requirement of several enzymes in specific conditions of the cell environment. For example, lac-operon produces lactose degrading enzymes only if lactose is the only energy source for the bacteria.
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