Cloning mammals

Scientists collect data to measure how successful cloning is in cattle. Table 1 shows the scientists’ data.

Calculate the percentage of embryos transferred that result in live calves being born.

Describe the stages in the production of a cloned mammal from an adult mammal.

There is some evidence that cloned cattle may have weakened immune systems. Explain why a weakened immune system can affect the health of cloned cattle.

Scientists also collected data comparing cloned cattle and a control group. Table 2 shows their results.

Comment on the effects of cloning on the growth and development of these cattle.

The passage gives information about cloning. Complete the passage by writing a suitable word in each blank space.

Animals such as sheep have been cloned. Cloning involves taking the_........ out of a diploid body cell from the sheep that is to be cloned. This structure is then placed into an_........ cell that has had its_........ removed. Electricity is used to help the cell to_........ by mitosis. This then develops into an_........ which is then placed into the _........ of an unrelated female. This female is known as the_........ mother.

Megalodon was an animal.

Which of these features does megalodon share with the fungus yeast?

1 nuclei present in cells

2 nervous coordination

3 stores carbohydrate as glycogen

Scientists think that the giant, predatory toothed whales that replaced the extinct megalodon consumed the same sources of food.

Explain how the evolution of giant, predatory toothed whales may have caused the extinction of megalodon. (lines 5 to 7)

Volcanoes release sulfur dioxide into the atmosphere.

Describe the biological consequences of sulfur dioxide release. (lines 10 to 12)

The release of large amounts of dust into the atmosphere reduced light intensity.

Explain why this would cause a loss of food chains. (lines 9 to 11)

Explain why the cells in cryozoos are put in salt and sugar solution rather than pure water. (lines 16 to 18)

Describe how scientists could clone a banteng. (lines 18 to 20)

Explain why releasing cloned mammoths could have negative and positive effects on Arctic biodiversity. (lines 22 to 28)

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.

Read the passage below.

Use the information in the passage and your own knowledge to answer the questions that follow.

Toystory

Toystory is a bull who was born in 2001. The photograph shows Toystory.

In the world of dairy farming Toystory is a famous bull. He fathered 500 000 offspring but did not mate with any cows. He was able to father so many offspring because his semen was collected and then used to fertilise cows using 5 artificial insemination.

Toystory’s mother was a high milk producer and his father was a popular bull. He was sold for $4 000 by his owner to a specialist breeding company called Genex.

Genex started to collect semen from Toystory when he was four years old. The semen is carefully collected, using a teaser animal and an artificial rubber vagina.

The semen is divided into many separate samples. These samples are put in small straws and frozen in liquid nitrogen. The straws can then be sold and sent to dairy farmers around the world to inseminate their cows. A total of 2.4 million samples of semen from Toystory was sold in more than 50 countries around the world.

Toystory’s reputation grew as the offspring he fathered went on to be high milk producers. His semen straws sold for over $60 each. Bull semen can now be sold as sexed or unsexed samples, with sexed samples being more expensive to 20 purchase.

Toystory was highly valued because his offspring produced large quantities of milk of a desired composition. His semen was effective at getting cows pregnant, his daughters gave birth easily and were strong. He had a rare mix of fertility, genetics and appearance.

One of his daughters sold for $300 000 in 2009. His record number of offspring is unlikely to be beaten. This is because bulls are often retired earlier as new genetic advances are discovered.

Suggest why Genex waited until Toystory was four years old before beginning to collect his semen (line 9).

Explain how the semen from the bull is used to fertilise cows using artificial insemination.

Suggest why the semen is stored in liquid nitrogen (line 13).

Sexed semen is guaranteed to produce offspring of one sex.

Suggest why dairy farmers would prefer to used sexed semen (line 19).

Determine the percentage success of Toystory’s semen samples in producing offspring (line 2 and line 15).

Describe how scientists could investigate which of two bulls is the best to use as a father in dairy farming.

Explain why the composition of milk is important to consumers (line 22).

Scientists are now using cloning to produce animals.

Describe the stages that are required to clone a bull.

Give two advantages of using cloning rather than selective breeding to produce offspring.

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

Give two reasons why blood clotting is important.

The optimum temperature for the enzymes involved in blood clotting is 37C. Sketch a graph to show how temperature affects the time taken for blood to clot.

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.

Explain why these mammals are described as transgenic.

Describe how a mammal is cloned.

The diagram shows a northern white rhino.

The northern white rhino is in danger of becoming extinct.

In 2018, there was only one left in the world.

This represents a 99.95% decrease in numbers from 1960 to 2018.

Calculate the population size of the northern white rhino in 1960.

Cloning was considered as a method to increase the northern white rhino population.

In 2018, the only northern white rhino left was an old female. Old females produce too few eggs for cloning to be successful.

Suggest two reasons why many eggs are needed for cloning to be successful.

Scientists are considering using semen from a southern white rhino to fertilise an egg from the northern white rhino.

Fertilisation would take place in a test tube and produce a zygote.

Name the cell in semen that fertilises the egg.

Explain what the scientists should do with the zygote so that it develops into a fetus.