Genetics
Transcript: Prosthetics, Cloning and Eugenics Cloning In 1901, Hans Spemann successfully split a 2-cell salamander embryo, which developed into two complete organisms. This showed that an early embryo cell has all the genetic information necessary to develop into a new organism. In 1914, he performed the first successful nuclear transfer experiments. Then, in 1938, Spemann published the book “Embryonic Development and Induction,” which explained the transfer of the nucleus of one egg (the somatic cell) into an enucleated egg cell. This became the basis for subsequent cloning experiments. In 1962, F. E. Steward was able to grow a complete carrot plant from a fully differentiated carrot root cell; this showed the possibility of cloning from differentiated cells. In 1998, a group of scientists in South Korea, called Clonaid, claimed to have cloned a human being. However, evidence did not exist to support this claim. Artificial Embryo Twinning: A two-celled embryo (or any early embryo) is manually separated into two individual cells, and each cell is left to divide on its own. After some time to allow for independent development (on a Petri dish), the two separate embryos are then implanted into a surrogate mother. The two babies should be genetically identical, since they are produced from the same zygote. Relevance: With cloning experiments, it has been shown that the genetic material of a completely differentiated somatic cell, not just a stem cell, can actually be used to generate an entire, new organism. This is because each somatic cell has a copy of the organism’s DNA. In each cell, certain genes from DNA may be ultimately expressed as specific proteins and drive the cell’s specific function. However, it seems as though this very specific gene expression is turned off when the nucleus of a somatic cell is isolated and placed into an egg cell. Originally, an egg cell would have a combination of genes (23 chromosomes from each parent in humans) given by the egg and sperm together. However, with SCNT cloning, the DNA of the egg cell is replaced with that of a somatic cell, which only contains genes from one individual. During the developmental phase, the early embryonic cells replicate their DNA and undergo mitosis. Even if clones are genetically identical, they are not always physically identical. The environment factors into how the organism forms and turns out. Also, some traits, such as the color and pattern of a female cat’s coat, involve randomly-occurring X chromosome inactivation, so it is not determined exclusively by DNA. Eugenics A Brief History Francis Galton, who coined the term eugenics in 1883, perceived it as a moral philosophy to improve humanity by encouraging the ablest and healthiest people to have more children. However, there is more negative definition of it: culling the “unfit” from the population by sending the people to asylums, sterilizing and sometimes even forcibly killing them. The movement became popular in the early 1900s under a backdrop of social unrest, war and the declining birthrate of the wealthy. Scientists and other supporters of eugenics saw that the population of the lower classes (those with less money and/or education) was rising rapidly while the population of the wealthy and educated was declining. Seeing that charity, religious organizations and social work were of little help to the urban poor, genetics was used to explain social problems such as poverty and criminality. In 1907, Indiana became the first state to pass a law permitting involuntary sterilizations on eugenic grounds; at least 30 states would follow suit. Many of them simply adopted a model "eugenical sterilization law," crafted by the Eugenics Record Office's (ERO) Harry Laughlin, which called for compulsory sterilizations of the "socially inadequate." By the mid-1920s, more than 3,000 people had been sterilized against their wills. These included the homeless, orphans, epileptics, the blind and the deaf. Also sterilized were those who scored poorly on IQ tests, who were diagnosed as being "feebleminded." In the late 1930s, eugenics began to lose popularity due to independent scientists’ investigations that disproved the theory. With the dawn of World War II and the Holocaust, which was done in the name of eugenics, the popularity of eugenics dried up, with organizations such as the ERO shutting down. However, states continued to forcibly sterilize people they deemed “feebleminded” or mentally ill until the 1970s, peaking with a time when 33 states were enforcing such practices. Methods of Research At its core, eugenics was an effort to apply Mendel's laws of inheritance to human traits. Since DNA has not yet been discovered, knowledge of heredity was limited to the perceivable physical manifestations of various traits. People of lower socioeconomic status as well as the mental and physically disabled were sterilized in the U.S. so that their “bad” genes could not further “infect the gene pool.” One such
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