Overview
Reproductive technology handles or preserves sperm, eggs and embryos outside the body to assist reproduction. Starting with livestock breeding, it now extends to human infertility treatment, conservation of endangered species and animals that produce medicines. It can be divided into techniques that assist sexual reproduction (artificial insemination, IVF) and techniques that create individuals asexually (cloning).
Artificial insemination and cryopreservation
Artificial insemination collects semen from a male and places it into a female's reproductive tract. Lazzaro Spallanzani's success with a dog in eighteenth-century Italy is known as an early case. In 1949 Polge, Smith and Parkes found that adding glycerol allowed spermatozoa to survive freezing and thawing, which made long-term storage and long-distance transport of semen possible. Today a single elite dairy bull's frozen semen can sire huge numbers of calves.
IVF and embryo transfer
In vitro fertilisation fertilises eggs with sperm outside the body and transfers the embryo to the uterus. Patrick Steptoe and Robert Edwards in Britain achieved the birth of Louise Brown, the first IVF baby, on 25 July 1978; Edwards received the 2010 Nobel Prize in Physiology or Medicine. In livestock, embryo transfer induces superovulation in an elite cow and moves the resulting embryos to recipient cows, spreading desirable traits quickly. Intracytoplasmic sperm injection (ICSI) and embryo freezing are also widely used.
Somatic cell nuclear transfer
Somatic cell nuclear transfer inserts the nucleus of a body cell into an enucleated egg and activates development, for example by an electric pulse, producing an individual genetically identical to the nucleus donor.
- In 1962 John Gurdon transferred nuclei from tadpole intestinal cells into frog eggs and obtained normal tadpoles, showing that nuclei of differentiated cells retain the genetic information for a whole organism. He shared the 2012 Nobel Prize with Shinya Yamanaka.
- Ian Wilmut's team at the Roslin Institute used the nucleus of an adult sheep's mammary cell to produce Dolly, born on 5 July 1996 and reported in Nature in 1997, the first mammal cloned from an adult somatic cell.
- Cattle, pigs, dogs, cats and other animals have since been cloned; in 2005 a Korean team produced Snuppy, a cloned dog.
Clones share nuclear genes but differ in mitochondrial DNA and uterine environment, so they are not perfectly identical, illustrating the interplay of nature and nurture. Low efficiency and reports of miscarriage, abnormalities and early ageing are further limits.
Transgenesis
Transgenesis introduces foreign genes into a fertilised egg or embryo to create animals with new traits, such as livestock that secrete human therapeutic proteins in their milk or animal models for disease research. Adding the gene to a somatic cell first and then performing nuclear transfer makes producing transgenic animals more efficient.
Ethics and law
Because reproductive technology intervenes at the beginning of life, it raises ethical issues such as human cloning, the moral status of embryos, surrogacy and loss of genetic diversity. In Korea, the Bioethics and Safety Act, enacted on 29 January 2004 and in force since 1 January 2005, prohibits human reproductive cloning by banning the implantation of cloned embryos in a uterus or their birth, and permits embryo research only under strict approval.
References
- Polge, C., Smith, A. U., & Parkes, A. S. (1949). Revival of spermatozoa after vitrification and dehydration at low temperatures. Nature, 164(4172), 666.
- Gurdon, J. B. (1962). The developmental capacity of nuclei taken from intestinal epithelium cells of feeding tadpoles. Journal of Embryology and Experimental Morphology, 10(4), 622–640.
- Steptoe, P. C., & Edwards, R. G. (1978). Birth after the reimplantation of a human embryo. The Lancet, 312(8085), 366.
- Wilmut, I., Schnieke, A. E., McWhir, J., Kind, A. J., & Campbell, K. H. S. (1997). Viable offspring derived from fetal and adult mammalian cells. Nature, 385(6619), 810–813.
- 「생명윤리 및 안전에 관한 법률」 (법률 제7150호, 2004. 1. 29. 제정, 2005. 1. 1. 시행).