1. In bacteria, the his operon is a repressible operon that encodes enzymes resp
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Question
1. In bacteria, the his operon is a repressible operon that encodes enzymes responsible for the production of the amino acid histidine. The co-repressor for the regulation of this operon is charged his-tRNAbis. For the following mutants, determine whether the operon genes will be transcribed, and briefly explain your reasoning. (6 points) e)mutation of the repressor, such that it cannot bind to charged his-tRNA his 2. What would be the response of E. coli to the addition of lactose if the bacterium contained a mutant, completely non-functioning lacY gene? Explain your reasoning. (4 points) 3. Using a couple of sentences each, describe the function of each of the following in regulating eukaryotic gene expression: a promoterExplanation / Answer
1.A Mutation in promoter inhibit the RNA polymerase binds here. So, no his will be produced here even absence of His molecules.
1. B Mutation in operator inhibits the binding of repressor to operator. So, even presence of His the operon will be active.
C. Mutation in repressor not able to bind in operator So, even presence of His the operon will be active.
2. lac y - is responsible for permease activity. If mutant in lacy gene the lactose can't able to enter into the cells
largely. So, lac operon will occur in slow manner or not operable.
3. A. Promoter - Transcriptional initiation site -35 and -10 positions. It promote recognition of transcriptional start sites by RNA polymerase. RNA polymerase binds here and starts its process.
B. Enhancer - It increase the activity of RNA polymerase at a given promoter by binding at different location of DNA.
C. Histone acetyltransferase - This enzymes involved in acetylation / deacetylation of histone in chromatin structure. Histone acetylation makes chromatin structure opens and these modified histones are found in regions
of the chromatin that are transcriptionally active. Histone deacetylation makes chromatin structure close
and transcriptional inactivity.
D. RNA-induced silencing complex (RISC) which separates the two RNA strands. The active strand of RNA derived either from the miRNA or siRNA pathway is anti-sense to a region of the target mRNA.
E. 5-methyl cytosine occurs in promoter regions of genes contain 10-20 times as many CpGs when compared to the rest of the genome. Methylated genes are transcriptionally silent and Non Methylated genes are transcriptionally active.
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