T4

Question 1

n egg cell from a cow was fertilised in a laboratory and allowed to develop into an eight-celled embryo. This was split into four parts, each of which developed into a new embryo. This is shown in the diagram. The new embryos were later transferred into different surrogate cows.

(a) Explain why the new embryos produced are a clone.

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(2)

(b) If embryos with more than eight cells are split up, the separated cells fail to develop into new embryos. Suggest why.

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(1)

(c) Give two advantages to a farmer of using embryos produced by this procedure.

Answer 1

(a) produced by mitosis;
genetically identical;

(accept identical genes / same genotype / WNA / genetic information)(reject same genes, same genetic code)

2

(b) cells lost ability to control development / no longer totipotent /
cells have differentiated / become specialised;

1

(c) (many) offspring with favourable characteristics / high meat / milk yield;
pedigree embryos into non-pedigree mothers / not risking pedigree
mothers / rare breeds conserved;
sex / gender selection;

2