Learning objectives for all sections involving cloning

• Know and understand that asexual reproduction can be used to produce individuals that are genetically identical to their parent.

• Appreciate that scientists can now add, remove or change genes to produce the plants and animals they want.

  • You are expected to use your skills, knowledge and understanding to:

    • interpret information about cloning techniques and genetic engineering techniques,

      • In the exam you may be given data to work from,

    • make informed judgements about the economic, social and ethical issues concerning cloning and genetic engineering, including genetically modified (GM) crops.

• Know and understand that new plants can be produced quickly and cheaply by taking cuttings from older healthy plants.

  • These new plants are genetically identical to the parent plant, ie clones or identical copies.

    • The cuttings are taken with a new bud on and planted in good quality moist compost where your cloned plant cutting should grow into a healthy new one.

• Know and understand that modern cloning techniques include:

  • Tissue culture – using small groups of cells from part of a plant.

    • Cells from part of a plant are grown in a suitable nutrient medium with added growth hormones.

    • These can be grown quickly, cheaply in large quantities at any time of the year.

  • Embryo transplants – splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.

    • Agriculture is using artificial insemination to produce high quality cattle - cloned offspring of prize bull - a lot of money can change hands over a prize bull eg hiring a prize bull for its sperm!

    • Egg cells from a 'prize cow' are artificially fertilised by sperm cells from the 'prize bull'.

    • After the resulting embryo has developed is split to form embryonic clones which can be implanted in other cows, who have become, 'artificially', the host mothers.

    • This means multiple quality offspring can be produced efficiently without waiting too long for 'mother nature'!

      • Cloning is a type of asexual reproduction producing cells that are genetically the same as the original starting cell.

      • Cloning reuses the same gene pool and so the gene pool is narrowed and if an organism (eg cattle) become susceptible to a disease, there are no animals in the herd to resist it.

      • Cloning can be used to help preserve endangered species.

  • Adult cell cloning – the nucleus containing the genetic material is removed from an unfertilised egg cell.

    • Know that this nucleus from an adult body cell, eg from a skin cell, is then inserted into the egg cell from which the original nucleus was removed ie the egg cell nucleus has been replaced with a complete set of chromosomes.

    • An electric shock stimulus then causes the egg cell to begin to divide to form embryo cells, just as a normal embryo would do.

    • These embryo cells contain the same genetic information as the adult skin cell.

    • When the embryo has developed into a ball of cells, it is inserted (implanted) into the womb of an adult female (surrogate mother) to hopefully continue its development from embryo ==> foetus ==> baby.

    • Although cloning is a successful technique, it is not without problems and raises social and ethical issues.

    • Cloning involves retaining the same restricted pool of DNA but it is providing valuable research into embryo development and cell aging and age related disorders.

    • Cloning mammals inevitably produces a reduced gene pool whereas sexual reproduction provides genetic variety.

    • The limited pool of alleles which make up chromosomes can make the species more susceptible to a contracted disease and other conditions such as premature aging, organ and immune system failures etc. (Look up the case of 'Dolly the Sheep').

    • The rate of successful cloning very low, genetic defects are common and those animals which survive the cloning procedure are often unhealthy and are much more susceptible to disease i.e. they are a 'genetically weak' animal.

    • If human cloning was attempted, it could lead to babies being born with disabilities, there is only a certain chance that an embryo would develop into a completely normal healthy baby - an ethical and moral dilemma for potential parents and the medical profession.

    • Cloning mammals is a means providing organs for transplants e.g. genetically modified pigs could be bred to provide donor organs for humans and cloning the pigs could meet the ever increasing demand from critically ill patients on the waiting list.

    • Cloning could be used to reproduce endangered animal species, whose numbers were falling dangerously low i.e. in danger of extinction.

• Revise any practical work you did to develop skills and understanding which may have included (which should also be revised, helps in understanding 'how science works' and context examination questions):

  • investigating the optimum conditions for the growth of cuttings, of, eg Mexican hat plants, spider plants, African violets,

  • investigating the best technique for growing new plants from tissue cultures (eg cauliflower).