Calculate the number of times the DNA of a modern E. coli cell has been copied accurately since its earliest bacterial precursor cell arose about 3.5 billion years ago. Assume for simplicity that over this time period, E. coli has undergone, on average, one cell division every 12 hours (this is an overestimate for modern bacteria, but probably an underestimate for ancient bacteria).

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#Question id: 10925

#Unit 7. System Physiology – Animal

During the second trimester of pregnancy, where is the predominant site of red blood cell production?

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#Question id: 29433

#Unit 6. System Physiology – Plant

Correct equation for Biological nitrogen fixation

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#Question id: 15843

#Unit 8. Inheritance Biology

You have isolated two temperature-sensitive mutations in phage l that you suspect may be in the same gene. These phage mutants are called ts-1 and ts-2. Each mutant will form plaques at 35˚C but not at 42˚C. You cross ts-1 to ts-2 phage by coinfecting E. coli at the permissive temperature of 35˚C. When the resulting phage lysate is plated at 35˚C you count 10,000 plaques per ml of phage lysate, but when the same phage lysate is plated at 42˚C, there are only 80 plaques per ml.           What is the distance between the ts-1 and ts-2 mutations in m.u.?

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#Question id: 15604

#Unit 12. Applied Biology

The bacteria which cause septicaemia are fast becoming resistant to the antibiotics used for controlling them. Which one of the following explanations fits best?

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#Question id: 27970

#Unit 1. Molecules and their Interaction Relevant to Biology

For the redox pair NAD/NADH, E is -0.320 V, and for the pair O2/H2O, E is 0.816 V.  The DE for this reaction is therefore 1.14 V, and the standard free-energy change △G’⁰ is