An allosteric transcription regulator called HisP regulates the enzymes for histidine biosynthesis in the bacterium E. coli. Histidine modulates HisP activity. On binding histidine, HisP alters its conformation, markedly changing its affinity for the regulatory sequences in the promoters of the genes for the histidine biosynthetic enzymes.   If HisP functions as a gene activator, would you expect that HisP would bind more tightly or less tightly to the regulatory sequences when histidine levels are low? Explain your answer.  

  Insulin is a small protein that regulates blood sugar level and is given to individuals who suffer from diabetes. Many years ago, diabetics were given insulin that had been purified from pig pancreas. Once recombinant DNA techniques became available, the DNA encoding insulin could be placed into an expression vector and insulin could be produced in bacteria. Which of the following is NOT a reason why purifying insulin from bacteria is a better way to produce insulin for diabetics than using insulin purified from a pig pancreas?  

  Across the plasma membrane, the Na+/K+ pump moves 3Na+ out and 2K+ in, which helps to maintain an overall negative charge in the cell (i.e., membrane potential of approximately -70 mV). Given this fact, (1) briefly explain why all cells have a negative membrane potential across the plasma membrane, then (2) consider the following scenario: What would you expect to happen to the membrane transport and cell functions if the Na+/K+ pumps were handicapped?  

  Which of the following is required for the secretion of neurotransmitters in response to an action potential?  

What do you predict would happen if you replace the Lac operator DNA from the Lac operon with the DNA from the operator region from the tryptophan operon?

  You have a linear piece of DNA that can be cut by the restriction nucleases HindIII and EcoRI, as diagrammed in Figure 10-4.   Figure 10-4   If you were to cut this linear DNA with HindIII, what type of DNA fragments do you predict you would obtain?  

  PCR involves a heating step, followed by a cooling step, and then DNA synthesis. What is the primary reason for why this cooling step is necessary?  

Which of the following statements about nucleosomes is true?

Which of the following news reports would be considered soft news?

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a colorblind son. What are the genotypes of the parents?   XN = dominant: normal color vision   Xn = recessive: colorblind