4101FSBMOL - REVISION - Practical Test.

Question 1

How many minutes do we have at each station?

Answer 1

8 minutes.

Question 2

What do we have to do at each station?

Answer 2

Do the calculation and then make up what is required.

Question 3

Question/ Station1:

How do you work out the amount of Solute required in Question 1?

What calculations are needed?

Answer 3

Work out what your concentration means - (e.g. 10mg/ml means 10mg in 1ml). Convert this into the required volume you need - (e.g. 100ml –> 10 x 100 = 1000mg/100ml). Convert to grams. This is essentially the weight value element for the starting concentration multiplied by the final volume needed and then all that divided by the starting volume element used in the starting concentration.

–> Start with ‘x’mg/‘a’ml.
–> (‘x’ mg x ‘b’ ml) / ‘a’ ml = ‘c’ mg.
–> End with ‘c’mg/‘b’ml.
–> CONVERT TO GRAMS IF NECCESSARY!

Question 4

Question/ Station 1:

How do you make up the required solution?

What is the essential last step we need to do?

Answer 4

1. Tare the balance.
2. Weigh out the solute into a weighing boat.
3. Add solute to a volumentric flask.
4. Add solvent (e.g. distilled water) up to the required volume needed.
5. Invert to mix.

6. LABEL THE FLASK! Include the name of the solution, concentration, initials and date.

Question 5

Question/ Station 2:

Whats the name of the type of Dilution you have to do?

Answer 5

Serial Dilution.

Question 6

Question/ Station 2:

How do you work out each of the concentrations in each tube?

Answer 6

An x-fold serial dilution means the next one is dividing the concentration of the previous by x amount. We made up A1 in Question 1. To do A2-A5, we half each time for a 2-fold. e.g. A1 = ‘x’mg/ml –> A2 = ‘x/2’mg/ml. REPEAT for all tubes.

Question 7

Question/ Station 2:

How do we make up A2-A5 solutions in the practical exam?

Answer 7

We made A1 in Part 1. For a 2-fold dilution, add half of A1 (previous solution) into tube A2 and then fill ther other half with distilled water/solvent we are using. Repeat for the rest of the tubes.

LABEL THE TUBES!

‘x’-fold means we divide the solution into ‘x’ parts. 2-fold means we have 2 parts –> 1 part solution, 1 part solvent. 3-fold would mean we have 3 parts –> 1 part solution, 2 parts solvent.

Question 8

Question/ Station 2:

What do we have to do with each of our samples once we have made them up?

What is the best order to do the samples in? Why?

Answer 8

Measure their absorbance using the Spectrophotometer - Single wavelength mode, blank and then measure concentrations.

REMEMBER A BLANK (A0)!

From Low to High Concentration. Because then you only need to use 1 cuvette for the samples and 1 for the blank - saves time!

Question 9

Question/ Station 3:

How do you calculate the Mean of the replicates of the sample?

Answer 9

EITHER - Add all the values up and divide by how many there are - OR - Type into your calculator using the statistics function - shows up as x̄.

Question 10

Question/ Station 3:

How do you calculate the Standard Deviation of the replicates of the sample?

Answer 10

Type into your calculator using the statistics function - shows up as sx.

Question 11

Question/ Station 3:

How do you calculate the Standard Error of the Mean of the replicates of the sample?

What is the formula?

Answer 11

Divide the Standard Deviation calculated by the square root of the amount of replicates of the sample.

S.D/√N.

Question 12

Question/ Station 4:

What equations do we need to use for this Question?

Answer 12

1. Molar (M) = moles (mol) / volume (L).
2. Moles (mol) = weight (g) / molecular weight (g/mol).

Question 13

Question/ Station 4:

How do we calculate the weight (g) using the equations?

Answer 13

Convert the Volume into Litres (L). Sub in the Molar and Volume into the first eqaution to find the moles. Sub this moles into the second equation along with the molecular weight and rearrange to find the weight required.

Question 14

Question/ Station 4:

How do we make up the required solution?

Whats the essential last step we need to do?

Answer 14

1. Tare the balance.
2. Weigh out the solute into a weighing boat.
3. Add the solute to a universal tube.
4. Add solvent (e.g. distilled water) up to the required volume needed.
5. Invert to mix.

6. LABEL THE FLASK! Include the name of the solution, concentration, initials and date.

Question 15

Question/ Station 5:

What things do we need to include in our risk assessment?

Answer 15

• CAS Number.
• State of substance.
• Hazard Code with statements.
• Route of Entry.
• Precautionary/Control Codes and statements.

Question 16

Question/ Station 6:

Explain how you would calculate the molecular weights of the fragments using Electrophoresis of a DNA sample.

Answer 16

Mention using the molecular weight markers to draw a graph of log molecular weight against RF value. RF value is obtained by measuring from the wells (top) to the bands for each standard and dividing this by the distance travelled by the dye front (bottom). The unknowns have their RF values calculated and then the graph is used to work out their molecular weights. Mention that smaller sizes travel further.

Essentially describe how to draw a graph and then calculate Rf Values.

Question 17

How do you calculate Rf Values?

Answer 17

Distance travelled by component/ distance travelled by solvent/dye front.

Question 18

Practical 6 - DNA Calculations:

How do you calculate the conc. of DNA in the partially purified sample using the absorbances?

Answer 18

1. Find the average of the Absorbances for Sample A and Sample B at 260nm.
2. Multiply this by the concentration of the known solution (50µg/ml in the practice).
3. Divide this by the absorbance of the known sample (1 in the practice).
4. Multiply this by the dilution factor.

Question 19

Practical 6 - DNA Calculations:

How do you calculate the conc. of DNA in the final, pure sample (C2)?

Answer 19

1. Use the absorbance at 260nm, and multiply this by the known conc. of 50µg/ml.
2. Divide this by the absorbance of the known sample.
3. Lastly, multiply this by the dilution factor.

Question 20

Practical 6 - DNA Calculations:

How do you determine the yield of your DNA?

Answer 20

• Amount = Concentration x Volume.
• Use the conc. of the pure sample and multiply this by voume it was diluted in to get the amount after purification.
• Yield = (amout after purification/ amount started with - partially purified sample) x 100.