Cloning & Biotechnology (OCR A Level Biology): Exam Questions

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.

[3]

(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 × 10⁶ bacterial 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 10cm³ solution.

• 0.1cm³ of 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]

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.

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]

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.

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]

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.

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]

Plant cloning is often used by farmers to produce new plants.

A plant that is often cloned by taking cuttings is lavender, Lavandula angustifolia.

A farmer had two fertiliser solutions, solution A and solution B, and wanted to investigate which one to use on lavender plants. In order to ensure the investigation would be valid, two cuttings were needed from the same parent plant.

(i) Describe how to clone a plant by taking a cutting.

[4]

(ii) The farmer grew one of the cuttings in soil fertilised with solution A and the other cutting in soil fertilised with solution B.

The farmer took several other precautions to increase the validity of the investigation, including:

• growing the plants in the same type of soil

• exposing the plants to the same light intensity.

After a set period of time the farmer measured the increase in height of the lavender plants. The farmer’s results are shown in the table below.

The farmer concluded that solution A increased the height of lavender more. A student said that, even though the investigation was valid, the results did not give strong support to the farmer’s conclusion.

Describe and explain how the investigation could be improved in order to have more confidence in any conclusions drawn from the results.

[6]

Cloning plants is also known as vegetative propagation.

Identify three advantages of vegetative propagation in agriculture.

Some humans are lactose intolerant. Milk can be treated with lactase to reduce the concentration of lactose present. Fresh milk is passed over lactase molecules immobilised on a suitable matrix.

Give two economic advantages of immobilising enzymes for large-scale production.

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

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