6.4.3 aritifical clones in animals

splitting an embryo to create 2 genetically identical embryos

removal of cell nucleus

technique involving transferring the nucleus from somatic cell to an egg cell

totipotent = divide & differentiate into all cell types found in adult organism

• elite farm animals produced by selective breeding (artificial selection) or genetic modification • genetically-modified animals developed with unusual characteristics

• embryo twinning/splitting • somatic cell nuclear transfer (SCNT)

• zygote is created by in vitro fertilisation (IVF) • zygote allowed to divide by mitosis to form small ball of cells • cells are separated & allowed to continue dividing • each small mass of cells is placed until uterus of surrogate mother

clone elite farm animals or animals for scientific research

egg & sperm used

phenotype is known before cloning starts

• an egg cell is obtained & it’s nucleus is removed = enucleation • normal body cell (somatic cell) from adult being cloned is isolated & may have nucleus removed • complete adult somatic cell (or it’s nucleus) is fused with empty egg cell by applying electric shock (electrofusion) • shock also triggers egg cell to start developing, as has just been fertilised • cell undergoes mitosis producing small batch of cells • young embryo placed into uterus of surrogate mother

(non-reproductive cloning) new tissues & organs can be grown as replacement parts of people who aren’t well

• skin can be grown in vitro to act as graft over burned areas • cloned cells have been used to repair damage to spinal cord of mouse & restore capability to produce insulin in pancreas • potential to grow whole new organs to replace diseased organs

• can produce whole herd of animals with high yield or showing unusual combination of characteristics • produces genetically identical copies of high value individuals who retain same characteristics • using genetically identical embryos & tissues for scientific research allows effects of genes/hormones be assessed without interference from different genotypes • testing medicinal drugs on cloned cells/tissues avoids animal testing • can produce cells/tissues genetically identical to donor, for use in repairing damage by disease/accidents • individuals from endangered species can be cloned to increase numbers

• lack of genetic variation may expose herd to diseases/pests & animals may be produced with little regard to their welfare which could have undesirable effects • success rate of adult cell cloning is poor & method is more expensive than conventional breeding so cloned animals may be less healthy & have shorter life spans • ethical issues regarding how long embryo survives & whether its right to destroy it • cloning individuals from endangered species & increasing numbers doesn’t increase genetic diversity