Double-stranded DNA is a cylinder that is 20A wide and 3.4A longper base pair. E. coli chromosome is a single double-stranded molecule that is 4.6 million bplong. An average E. coli cell is a cylinder that is 2 ?m longand 1 ?m in diameter (1 ?m = 10,000 A). Given […]

1. Researchers have identified an E.coli strain having constitutive expression of camp. What would be the effect on lac operon expression in the following media? What if this mutant also contained an O^- mutation? a. Glucoseb. Lactosec. Glucose + Lactose 2. A mutant strain of E.coli has constitutive expression of […]

a. Write out the reaction equilibria for the sequential deprotonation of tyrosine and the equations for the corresponding Ka for each. (Hint: There should be three reaction equilibria.) You may abbreviate tyrosine as Tyr and indicate the appropriate number of hydrogens and charge (i.e., H3Tyr+ for fully protonated tyrosine). Also […]

Mammalian cells were grown in a cell culture medium that contains large amounts of uracil labeled with radioactivity on the two nitrogens in the uracil ring.  Assume that this radioactivity nitrogen remains in uracil and cannot be transferred to any other molecule.  Which of the following molecules would probably contain […]