Cloning

Question 1

Describe reproductive cloning

Answer 1

Produce a duplicate of an existing animal
Produces several genetic defects
Genetic material from embryonic, feral or adult cell removed and placed into an unfertilised and enucleated egg or embryo (with own mitochondria)
Nuclear and mitochondrial genes are different
Has the potential to create many clones
DNA has to be reprogrammed to change to epigenetic markers back the embryonic state

Question 2

Describe therapeutic cloning

Answer 2

Somatic cell nuclear transfer

• Remove nucleus from egg cell
• Replace with nucleus from somatic cell
• Stimulate cell division- allow embryo to grow to blastocyst stage in vitro
• Develop and produce stem cells
• Stem cells are removed from pre-embryo
• Grown into specific organ
• Transplant into patient

Question 3

Describe the cloning of dolly the sheep

Answer 3

Treat the ewes with gonadotropin-releasing hormone which causes them to produce oocytes ready to be fertilised
Plunge a micropipette over the polar body and suck out the haploid pronucleus and the polar body
Mammary cells from the adult Finn Dorset ewe are grown in tissue and deprived of nutrients to put them into quiescence
Donor cells and enucleated cells are put in culture together and subjected to electric pulses so their membranes fuse and stimulate the cell to continue mitosis- simulating fertilisation
Grown into a blastocyst and imkAbyed in the uterus of a Scottish blackface ewe
Knew when she was born if she was a clone of the Finn Dorset because she had a white face and the surrogate mother had s black face

Question 4

What are the problems with Dolly’s cloning and with productive cloning in general?

Answer 4

Dolly’s telomeres had already accumulated 6 years of damage- they are known to protect the end of the DNS from exonucleases
In respect to mitochondrial DNA she us not a clone of the Finn Dorset
Most cloned embryos derived from SCNT die during gestation or early on after birth, those that don’t get respiratory problems as an adult
Many have developmental disorders associated with an enlarged placenta, have metabolic disorders, diabetes or neurological disorders
Placenta development, respiratory problems and diabetes can be associated by imprinted genes- misregulation of these through epigenetic inheritance may be a barrier to normal development in cloned animals

Question 5

Describe embryo cloning

Answer 5

Occurs in nature- identical twins- totipotent cells split and separate
Embryo splitting- artificially splitting a single embryo at a very early stage of development- up to the 8 cell stage
Both nuclear and mitochondrial genes will be the same