Cloning (Edexcel IGCSE Biology)

Micropropagation is used to produce plant clones.

The process involves growing explants in vitro.

State what is meant by the term in vitro.

The explants grow new roots and shoots.

A student investigates the effect of pH on the growth of new shoots.

The table shows the student’s results.

(i) Explain the relationship between pH and the mean number of shoots per explant.

(2)

(ii) Describe a procedure the student could use to obtain explants and produce these results.

(6)

Give two benefits of using micropropagation to produce new plants rather than using seeds.

Blood clotting is an important process in humans. The process is controlled by enzymes.

(i) Give two reasons why blood clotting is important.

(2)

(ii) The optimum temperature for the enzymes involved in blood clotting is 37°C.

Sketch a graph to show how temperature affects the time taken for blood to clot.

(1)

Some people cannot make the proteins needed for blood clotting.

Cloning is used to produce large numbers of transgenic mammals.

These transgenic mammals can make the human blood-clotting proteins. The human blood-clotting proteins can then be removed from the mammals’ milk and injected into people who cannot make the proteins.

(i) Explain why these mammals are described as transgenic.

(2)

(ii) Describe how a mammal is cloned.

(6)

Scientists have produced cloned monkeys. The diagram shows the procedure used to produce cloned monkeys

(i) State the meaning of the term enucleated.

(1)

(ii) Describe how the single cell develops into an embryo.

(2)

Scientists can use adult body cells or fetal body cells to clone monkeys.

The table gives information about cloning using body cells from different sources.

Evaluate this data to decide which source of body cells is more successful in cloning monkeys.

Many mammals have been cloned since Dolly the sheep was produced by cloning in 1996.

It took 277 attempts at cloning to produce one sheep.

Calculate how many attempts would have been needed to produce 50 cloned sheep in 1996.

Assume the same number of attempts are needed to produce each sheep as were needed to produce Dolly.

Describe the stages used to clone a male dog.

Pet owners can now pay scientists to use cells from their pet to produce a clone.

The process costs $50 000 for a dog and $25 000 for a cat.

Cloning is not always successful and as with Dolly, many attempts may need to be made to produce one clone.

Many scientists disagree with this use of cloning.

Comment on whether cloning of pets is a good idea.

Use the information in this question and your own knowledge to support your answer.

The lady's slipper orchid (Cypripedium calceolus) is extremely rare in the UK.  

Björn S..., CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

Conservationists are keen to reintroduce the species into the wild and are using a variety of breeders from around the world to provide plants. 

Another method to help with the reintroduction is to produce clones of the orchid which can be planted in the wild.

Describe how micropropagation can be used to produce large numbers of lady's slipper orchid individuals.

Some people argue that using this method to clone lady's slipper orchids is a good method for growing orchids to use as house plants, but not for reintroduction to the wild.

Explain why cloning lady's slipper orchids in this way may not be a suitable method for producing plants to be reintroduced into the wild.

During a conservation attempt, scientists planted 126 Lady's slipper orchids. Of the orchids planted, 13 were still growing a year later while the rest had died. 

(i) Calculate the percentage of orchids that survived the year. 

(1)

(ii) Suggest two reasons why so many of the Lady's slipper orchids died in the space of a year.

(2)

(iii) The scientists decided to try again and plant more orchids in the area in a second conservation attempt.

Suggest two strategies the scientists could use to increase the success of the second attempt. 

(2)

Describe how plants are able to reproduce asexually without human intervention.

Micropropagation is a form of asexual reproduction in plants.

Compare the asexual reproduction you described in part (a) with micropropagation. 

Design an investigation to find out whether adding more amino acids to nutrient media during micropropagation affects the growth of the new plants.

Your answer should include experimental details and be written in full sentences.

New medical technologies have the potential to use human stem cells to treat patients with previously incurable diseases, such as type 1 diabetes. 

The diagram below shows one such strategy.

(i) Compare the process shown in the diagram with the method used to clone mammals, such as Dolly the sheep. 

(4)

(ii) Name one other condition that could theoretically be treated using this method. 

(1)

It is thought that the method shown in part (a) will be better for patients than using stem cells taken from a human donor, e.g. umbilical cord cells.

Explain the benefit of using cells produced by the method shown in (a) rather than cells from a human donor.

State two reasons why some people may be concerned about using stem cells in the way shown in part (a).

The unfertilised eggs from a donor, shown in part (a), can be stored in a special nutrient solution before they are combined with a skin cell nucleus.

Design an investigation to find the best storage temperature for the survival of the unfertilised eggs.

Your answer should include experimental details and be written in full sentences.

There are a number of wild species of banana that contain large seeds in their fruits, as shown in the diagram below.

The varieties of banana that humans consume do not have large seeds, which improves the experience of eating them.

Seeds play an important role in sexual reproduction in plants and therefore it is not possible for any species to naturally evolve to produce seedless fruit.

Explain how it is possible for humans to develop varieties of bananas without seeds.

Bananas without seeds cannot reproduce sexually. 

A low-income farmer who grows bananas in rural South America must decide whether to use cuttings or micropropagation to produce new plants for his farm. 

Discuss which method would be the most suitable for the farmer to use. 

A type of fungal pathogen called Fusarium oxysporum infects banana plants and causes a disease called Panama disease. The fungal spores live in the soil and can pass from plant to plant in water droplets. 

A variant of banana called Cavendish accounts for around 99 % of all banana exports to developed countries. 

The Cavendish banana is vulnerable to Panama disease. 

Using information from the question and your own knowledge, explain why this disease poses such a large threat to crop varieties of banana plants.