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TLS Online TPP Program

#Question id: 15654

You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium. Next you isolate a mutation, designated MelB–, which gives uninducible melibiase activity. Mapping experiments show that MelB– is linked to Mel1. Using an F' factor that carries the chromosomal region surrounding Mel1, you perform the following genetic tests:

                      
Describe the basic genetic properties of the MelB– mutation?

#SCPH01 Biochemistry
  1. MelB- is a dominant mutation whose wild-type allele codes for a trans-acting factor that is not Mel1
  2. MelB- is a recessive mutation whose wild-type allele codes for a cis-acting factor that is not Mel1
  3. MelB- is a dominant-recessive mutation whose wild-type allele codes for a cis-acting factor that is not Mel1
  4. MelB- is a recessive mutation whose wild-type allele codes for a trans-acting factor that is not Mel1
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TLS Online TPP Program

#Question id: 382

#SCPH05 I Biotechnology

The molar ratio of sodium acetate to acetic acid in a buffer solution with a pH OF 5.76 is 10:1. Assuming the total buffer concentration is 2.2 X 10-2 mol/L, how many grams of sodium acetate (m.w. 82) and how many grams of acetic acid (m.w. 60) should be used in preparing a litre of the solution?
TLS Online TPP Program

#Question id: 383

#SCPH05 I Biotechnology

Three buffers are made by combining a 1 M solution of acetic acid with a 1 M solution of sodium acetate in the ratios shown below

1 M acetic acid              

1 M sodium acetate  

Buffer 1: 10 mL

 90 mL

Buffer 2: 50 mL

50 mL

Buffer 3: 90 mL

10 mL

 Which of these statements is true of the resulting buffers?
TLS Online TPP Program

#Question id: 383

#SCPH05 I Biotechnology

Three buffers are made by combining a 1 M solution of acetic acid with a 1 M solution of sodium acetate in the ratios shown below

1 M acetic acid              

1 M sodium acetate  

Buffer 1: 10 mL

 90 mL

Buffer 2: 50 mL

50 mL

Buffer 3: 90 mL

10 mL

 Which of these statements is true of the resulting buffers?
TLS Online TPP Program

#Question id: 384

#SCPH05 I Biotechnology

A solution was prepared by dissolving 0.02 moles of acetic acid (HOAc; pKa = 4.8) in water to give 1 liter of solution. What is the pH? To this solution was then added 0.008 moles of concentrated sodium hydroxide (NaOH). What is the new pH? (In this problem, you may ignore changes in volume due to the addition of NaOH).
TLS Online TPP Program

#Question id: 384

#SCPH05 I Biotechnology

A solution was prepared by dissolving 0.02 moles of acetic acid (HOAc; pKa = 4.8) in water to give 1 liter of solution. What is the pH? To this solution was then added 0.008 moles of concentrated sodium hydroxide (NaOH). What is the new pH? (In this problem, you may ignore changes in volume due to the addition of NaOH).
TLS Online TPP Program

#Question id: 385

#SCPH05 I Biotechnology

In which reaction below does water not participate as a reactant (rather than as a product)?