Leq: what is cloning and how is it done?11.10 to 11.12

Cloning

Cloning is the creation of a genetic copy of a sequence of DNA or of the entire genome of an organism

There are three basic types of cloning

1. Recombinant DNA technology – the transfer and copying a segment of DNA from one organism to another

2. Reproductive cloning – generating an entire organism that is genetically identical to an existing organism

3. Therapeutic cloning- the production of human embryos for the purpose of harvesting stem cells for research purposes

Dolly The 1st successful mammal clone created from a specialized body cell.

Created at the Roslin Institute of Edinburgh University under the direction of Ian Wilmut

There was concern that she would be born “old” because her DNA was from an adult sheep. Her telomeres were shorter than other sheep of her age but not as short as an “old” sheep. This could have played a role in her short life span (6 years – normal 11 to 14 years)

Before she died of cancer she was able to give birth to 6 lambs, the first of which was named Bonny

Reproductive CloningEgg cell nucleus (haploid) is removed and replaced with a somatic cell nucleus (diploid)

The egg cell is stimulated to induce cell division;

Once the dividing egg cell reaches the embryo stage it is implanted into a surrogate mother

The embryo develops into a living organism

Benefits and Problems with Reproductive CloningBenefits:

Genetic Research

Restock populations of endangered animals

Insure that “good” genes are passed to the next generation

Problems:

Costly and inefficient (90% of the time it doesn’t work)

Short lifespan

Susceptible to disease and illness results in early death

Ethical Issues with Reproductive CloningTechnical and medical safety Undermining the concept of reproduction and family Ambiguous relations of a cloned child with the progenitorConfusing personal identity and harming the psychological development of a cloneConcerns about eugenicsContrary to Human Dignity Promoting trends towards designer babies and human enhancement

Therapeutic CloningFollow similar steps to reproductive cloning placing a somatic cell nucleus into an empty egg cell and stimulating cell division

Big Difference – the embryo is never implanted into a surrogate

Instead, once the dividing egg reaches the blastocyst stage in development stem cells are harvested

Embryonic stem cell lines are then established for research purposes

Benefits and Problems with Therapeutic CloningBenefits:

The stem cells harvested can develop into any type of cell; Can be used to develop treatments to diseases and possibly be used to create tissues/organs for transplant purposes without worrying about rejection by the immune system

Problems:

Costly and inefficient; requires that the embryo be destroyed so that stem cells can be harvested (is a blastocyst a living being?)