Define operons as they occur in bacterial cells. What will be an ideal response?
Bacterial operons are functionally related genes that are regulated together .
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Active -galactosidase enzyme is observed only in E. coli growing in the presence of lactose. One hypothesis is that the enzyme is always being produced, but is produced in an unstable form that breaks down rapidly in the absence of lactose (hypothesis 1)
A second hypothesis is that the enzyme is stable, but is produced only in the presence of lactose (hypothesis 2). An experiment was performed to test these hypotheses. A culture of growing cells was exposed to lactose, which was later removed. The amount of -galactosidase present in the culture during the course of the experiment was measured. The data are shown in the graph below. Which one of the following statements is a conclusion that can be obtained from these experimental data? A. The amount of -galactosidase in the culture decreased rapidly after lactose was removed, in support of hypothesis 2. B. The amount of -galactosidase in the culture decreased rapidly after lactose was removed, in support of hypothesis 1. C. The amount of -galactosidase in the culture remained stable after lactose was removed, in support of hypothesis 1. D. Synthesis of -galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 2. E. Synthesis of -galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 1.
Which of the following events do not occur in non-stop mRNA decay?
A. A string of lysine residues are added at the C-terminus of the polypeptide. B. The stalled ribosome recruits Ski7 protein. C. Ski7 protein degrades the defective protein by recognizing the C-terminal poly(Lys) tag. D. An exosome ribonuclease degrades the mRNA.
Bully whippets are unable to synthesize:a
testosterone. b. growth hormone. c. estrogen. d. progesterone. e. myostatin
This student has probably found a(n) _____
A) bryophyte sporophyte B) fern sporophyte C) horsetail gametophyte D) lycophyte sporophyte