Animal Cloning

Question 1

Give an example of a natural animal clone

Answer 1

-during sexual reproduction, once an egg has been fertilised, it’s possible for it to split during the very early stages of development and develop into multiple embryos with the same genetic information. The embryos can develop as normal to produce offspring that are all genetically identical-they are clones. E.g identical twins

Question 2

Explain the method of artificial embryo twinning

Answer 2

1) an egg cell is extracted from a female cow and fertilised in a Petri dish
2) the fertilised egg is left to divide at least once, forming an embryo
3) the individual cells from the embryo are separated and each is put into a separate Petri dish. Each cell divides and develops normally, so an embryo forms in each Petri dish
4) the embryos are then implanted into female cows, which act as surrogate mothers
5) the embryo continues to develop inside the surrogate cows, and eventually the offspring are born. They’re all genetically identical to each other

Question 3

Explain the method for somatic cell nuclear transfer

Answer 3

-this method is a bit more high tech then artificial embryo twinning

1) a somatic cell is taken from sheep A. The nucleus is extracted and kept
2) an oocyte (immature egg cell) is taken from sheep B. It’s nucleus is removed to form an enucleated oocyte
3) the nucleus from sheep A is inserted into the enucleated oocyte from sheep B. This now contains the genetic information from sheep A
4) the nucleus and the enucleated oocyte are fused together and stimulated to divide (e.g by electrofusion). This produces an embryo
5) then the embryo is implanted into a surrogate mother and eventually a lamb is born that’s a clone of sheep A

Question 4

Explain what some of the many uses of animal cloning are

Answer 4

1. For research purposes e.g in the field of medicine they can test new drugs on cloned animals. They’re all genetically identical so the variables that come from genetic differences are removed
2. Used to save endangered animals from extinction by cloning new individuals
3. Used in agriculture so farmers can increase the number of animals with desirable characteristics to breed from
4. Some scientists only want the cloned embryonic stem cells. These cells are harvested from young embryos and have the potential to become any cell type, so scientists think they could be used to replace damaged tissues in a range of diseases e.g heart disease as they won’t be rejected from the patients own immune system

Question 5

What are the arguments for animal cloning?

Answer 5

-desirable genetic characteristics are always passed on to clones. This doesn’t always happen with sexual reproduction
-infertile animals can be produced
-increasing the population of endangered species to help preserve biodiversity
-animals can be cloned at any time, don’t need to wait for breeding seasons
-cloning can help us develop new treatments for disease, which could mean less suffering

Question 6

What are the arguments against animal cloning?

Answer 6

-very difficult, expensive and time consuming
-no genetic variability in cloned populations so undesirable characteristics are always passed on. This means all susceptible to same diseases which could wipe out whole population
-some evidence suggests that clones might not live as long as natural offspring so maybe unethical
-using cloned human embryos as a source of stem cells is controversial. The embryo is usually destroyed after the embryonic stem cells have been harvested which may be unethical as destroying a human life