Meiosis in humans produces cells that participate in fertilization. Outline the processes involved in meiosis.

Following fertilization, cells in the developing embryo differentiate. Outline a technique for cloning using differentiated animal cells.

Discuss ethical issues of therapeutic cloning in humans.

Remember, up to TWO “quality of construction” marks per essay.

a. meiosis reduces a diploid cell into (four) haploid cell(s);
b. (during prophase I) homologous chromosomes pair up/synapsis;
c. chromatids (break and) recombine / crossing over
d. (metaphase I) (homologous chromosomes) at the equator of the spindle / middle of cell;
e. (anaphase I) (homologous) chromosomes separate and move to opposite poles;
f. (telophase I) chromosomes reach poles and unwind WTTE;
g. (prophase II) chromosomes (condense and) become visible, new spindles form;
h. (metaphase II) chromosomes line up at the centre of the cells/equator;
i. (anaphase II) sister chromatids separate;
j. (telophase II) chromatids reach the poles and unwind;

Remember, up to TWO “quality of construction” marks per essay.

a. differentiated/somatic/diploid cells taken from donor animal/sheep udder;
b. (diploid) nucleus from donor cells removed;
c. ova/eggs cells removed from (donor) animal/female sheep;
d. (haploid) nucleus removed from eggs/ova;
e. (diploid/donor’s) nucleus is fused with/inserted into egg/ovum (to form zygote);
f. embryo (from cell with donor nucleus and egg from surrogate) implanted in uterus of surrogate mother;
g. normal pregnancy and birth is completed;
h. offspring is a genetic copy/clone of the donor mother/diploid nucleus WTTE;

Remember, up to TWO “quality of construction” marks per essay.

a. therapeutic cloning involves producing embryos from which embryonic stem cells can be harvested for medical use;

argument in favour:
b. (to many people) any procedure that reduces pain and suffering is ethically/morally justified;
c. stem cells can be used to replace organs/tissues that have been lost/damaged in a patient;
d. (thus) pain and suffering can be reduced/lives can be saved/life quality improved;
e. cells can be removed from embryos that have stopped developing and would have died anyway;
f. cells are removed at a stage when no pain can be felt by the embryo;
g. use embryos from IVF that would otherwise be destroyed;

Accept up to one additional reasonable argument in favour.

argument against:
h. embryonic stem cells are no longer needed as adult stem cells can be used without causing loss of life;
i. there is danger of embryonic stem cells developing into tumour cells/harmful effects are not yet known;
j. every human embryo is a potential human with the right to development;
k. more embryos may be produced than can be used and so some would be killed;
l. (to many people) any procedure that harms a life/kills is unethical/morally wrong;
Accept up to one additional reasonable argument against.

To award [8] at least one pro and one con must be addressed.

Most had an idea that four haploid cells formed from one diploid and were able to outline the stages of meiosis.

The technique of cloning was not well understood, with many mixing it up with IVF. The origins of the differentiated cells and the ova were often confused.

Therapeutic cloning was not well understood, and again confused with IVF. Many answers conjured up ideas of human clones kept in laboratory cupboards from which organs could be harvested when needed. The answers seemed to be centre specific, with students from centres where it was discussed in detail scoring well. There were several comments about the fact that it was allocated 8 marks for ethical issues, whereas the other two parts were only awarded 5 each. It is an extremely important topic, which may have far reaching consequences for the students in the future.