Cloning & Biotechnology (OCR A Level Biology)

Exam Questions

1 hour23 questions

1 mark

Tannase is an enzyme produced by some microorganisms. Tannase is useful in many industrial applications including food production.

The tannase used in food production can be free in solution or immobilised.

State one method by which tannase could be immobilised.

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8 marks

Scientists compared the activity of free tannase and immobilised tannase. They investigated the activity of tannase over a range of pH.

The results are shown in the graph.

q17b-paper-2-nov-2020-ocr-a-level-biology

(i)

Calculate how many times more active immobilised tannase is compared to free tannase at pH8.0.

Give your answer to an appropriate number of significant figures.

number of times = .......................................................... [2]

(ii)

Draw a line of best fit for the free tannase on the graph.

Answer on the graph .................................................[1]

(iii)

A student concluded that the optimum pH for this tannase enzyme is pH5.8.

Explain why the data in the graph might not support the student’s conclusion.

[3]

(iv)

The results suggested that immobilised tannase was more stable over a range of pH values than free tannase.

Explain why immobilised tannase is more active at pH8 than free tannase.

[2]

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3 marks

Immobilised enzymes are often active over a greater pH and temperature range than free enzymes.

Using immobilised enzymes can be cheaper than using free enzymes.

(i)

Suggest two reasons why using immobilised enzymes in industrial processes could be cheaper than using free enzymes.

[2]

(ii)

State one disadvantage of using immobilised enzymes in industrial processes.

[1]

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9 marks

Bacteria and fungi can be used to make food for human consumption. The use of microorganisms in food production creates fewer ethical issues than the use of animals.

(i)

Using examples, describe and explain some other advantages of using microorganisms to produce food for human consumption.

[6]

(ii)

On an industrial scale, microorganisms can be cultured using either batch fermentation or continuous fermentation.

The table below lists statements about industrial culturing of microorganisms.

Place ticks (✓) in the table to indicate whether each statement applies to batch or continuous fermentation.

Statement	Batch	Continuous
Waste is removed during the fermentation process
A fixed volume of nutrient medium is used
Secondary metabolites are more likely to be produced
The growth rate tends to be faster
The culture is grown for a fixed period of time

[3]

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4 marks

(i)

Serial dilutions can be used to estimate the size of a bacterial population in a culture.

A scientist used 20cm³ of a bacterial culture that contained 1.0 × 10⁶bacterial cells.

5% of the 20cm³ culture was transferred to a new test tube and made up to 10cm³ with water.
An additional ten-fold dilution was carried out, which produced a final 10cm³solution.
0.1cm³of the final 10cm³ solution was transferred to an agar plate.

Each colony that developed on the agar plate was assumed to represent a single bacterial cell in the bacterial culture.

Estimate the number of colonies that you would expect to develop on the agar plate.

number of colonies = .......................................................... [3]

(ii)

A student carried out a different serial dilution to estimate the size of another bacterial population.

The serial dilution resulted in four colonies developing on an agar plate.

Explain why the student’s estimation of this bacterial population is likely to be inaccurate.

[1]

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4 marks

It is possible to clone animals using a technique called somatic cell nuclear transfer (SCNT).

The most well-known example of this was the cloning of Dolly the sheep in 1996.

Thirty years before Dolly the sheep, successful cloning of an animal was carried out using a frog, Xenopus laevis.

Frogs lay eggs in water. These eggs then develop and hatch into swimming tadpoles. When the tadpoles grow to a certain size they develop into adult frogs.

The cloning process is outlined in Fig. 19.1.

q19a-paper-2-june-2019-ocr-a-level-biology

Fig. 19.1

(i)

Describe what is happening at stage A and suggest a practical procedure that could allow this to occur.

[2]

(ii)

Identify a key difference between the processes between stages A and C and the cloning of Dolly the sheep.

[1]

(iii)

The frog produced by the process in Fig. 19.1 is not a complete clone of the donor tadpole.

Suggest why the cloned frog might not be considered a complete clone of the donor tadpole.

[1]

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5 marks

The success of SCNT has been investigated in many species.

Sheep are more closely related to mice than they are to Xenopus frogs.

Fig. 19.2 shows the percentage of SCNT procedures that were successful in mice and Xenopus when the donor nucleus was taken from cells at different stages of development.

The Xenopus data were published in 1962.
The mouse data were published in 1998.

q19b-paper-2-june-2019-ocr-a-level-biology

Fig. 19.2

(i)

Suggest why the x-axis does not show the age of the donor nuclei.

[2]

(ii)

Dolly the sheep suffered health problems throughout her life and died at an early age.

The donor nucleus that was used to create Dolly came from a sheep that was already five years old. The normal lifespan of a domestic sheep is ten years.

A student concluded that Dolly’s health problems were caused by the stage of development of the sheep that provided the donor nucleus.

List three reasons why the information in Fig. 19.2 does not support the student’s conclusion.

1 .........................................................

2 .........................................................

3 ........................................................

[3]

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5 marks

One measure of the success of cloning procedures is the number of pregnancies that result in live births.

Table 19 shows information from the work of many scientists about the success of SCNT in four different species.

Species	Number of pregnancies	Number of live births
Goat	26	8
Monkey	3	2
Mouse	438	56
Sheep	110	48

Table 19

(i)

Calculate the percentage of pregnancies that resulted in live births in goats and mice.

live births in goats = ................................................ %

live births in mice = ................................................ %

[2]

(ii)

Compiling results from different scientists can have problems as their investigations may not have been controlled in the same way.

List three factors that should have been controlled when compiling the data to include in Table 19.

1 ...........................................................................

2 ...........................................................................

3 ...........................................................................

[3]

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Fertiliser solution	Increase in height (cm)
A	20.3
B	15.4