Question

1. Can a protein begin to fold whole it is still being synthesized on the ribosome?

2. With the TRP in E.coli encoding the components necessary for tryptophan biosynthesis. The amino acid is considered a co-repressor, so in the prescence of the amino acid( select all that apply):

a. the operon genes are expressed

b. the expression of the tryptophan repressor is shut off

c. the tryptophan operator is bound to the t repressor

d. the t repressor is bound to bacterial RNA polymerase

3. Cis regulatory siters can be in locations distant from the gene. Under which of the following conditions is the Lac operon in E. Coli fully turned on?

a. Low cAMP and high glucose levels

b. Low glucose and lactose levels

c. High lactose levels and low glucose

d. High glucose and High lactose levels

4. What is X-inactivation mediated by the action of?

a. Antisense RNA

b. Chromatin structure

c. DNA methylation

d. Non coding RNA

Answer 1

1- no

the transcription and translation can occur simultaneously in prokaryotes but the prtein folding does not occur simultaneously both in eukaryotes and prokaryotes.After being translated from mRNA, all proteins start out on a ribosome as a linear sequence of amino acids. This linear sequence must “fold” during and after the synthesis so that the protein can acquire what is known as its native conformation

2-

b. the expression of the tryptophan repressor is shut off

c. the tryptophan operator is bound to the t repressor

reason- when the end product tryptophan is sufficiently produced it acts as co repressor and activate the repressor to bind actively to the operator thus the transcription gets stopped. thus the expression of tryptophan repressor is shut off and the operator is bound to repressor efficiently

3-b. Low glucose and lactose levels

the operon system only gets on when the form of lactose which is allolactose induces the operon to form the product. it occurs when the glucose and lactose level are low thus the cell needs energy and operon system in switched on

4- c dna methylation

DNA methylation plays a key role in X-chromosome inactivation (XCI), a process that achieves dosage compensation for X-encoded gene products between mammalian female and male cells