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DNA: The Code of Life

Summary

Back even thirty years ago, the thought of creating a living copy of a higher form of life was considered science fiction. Now, science fiction has become science fact. In the Stargate SG-1 universe, members of SG-1 have encountered many advanced cultures and alien races which have mastered the art of creating copies of higher life forms, such as those of a human being. Although some of the methods imagined are still way out in the realm of science fiction, there are some elements of fact hidden behind the stories brought forth.

The word "cloning" can be applied to the many levels of duplicating living cells, tissues, organs, and organisms. Surprisingly enough, botanists and gardeners have cloned for many years through grafting. There are some species of shrimp which produce asexually, or through cloning, naturally. The word "clone" itself can be defined as "a group of replicas of all or part of a large biological molecule" (such as DNA). The main thrust of cloning is that it is biological.

History of Cloning on Earth

Scientists created the most famous clone of a higher life form in 1997 with the birth of Dolly, the sheep clone. Dolly lived for six years, dying by lethal injection in 2003. Her lifespan was about half the usual for a sheep of her kind. She suffered from lung cancer and crippling arthritis. Scientists claim, however, that other than the cancer and arthritis, Dolly was normal. She was even the mother of six lambs, reproducing the "old fashioned way."

Dolly was produced by a method of cloning called "reproductive cloning." In this method, scientists transfer genetic material from the nucleus of a donor adult cell to an egg whose nucleus, and thus its genetic material, has been removed. The reconstructed egg is treated with chemicals or electric current in order to stimulate cell division and once the cloned embryo reaches a suitable stage, it is transferred to the uterus of a female host where it continues to develop until birth.

This method of cloning does not produce an identical clone of the donor animal. Only the clone's chromosomal or nuclear DNA is the same as the donor while some of the clone's genetic materials come from the mitochondria in the cytoplasm of the enucleated egg.

The source of Dolly's donor cell was an udder cell which was reprogrammed to generate an entire new organism, rather than just more udder cells. Scientists believe that errors or incompleteness in the reprogramming process cause the high rates of death, deformity, and disability observed among animal clones.

There are other forms of cloning practiced by our scientists today. One form of cloning is called "therapeutic cloning," or "embryo cloning." The goal of this process is not to create cloned human beings, but rather to harvest stem cells that can be used to study human development and to treat disease.

The form of cloning called "recombinant DNA technology," "DNA cloning," "molecular cloning," or "gene cloning" all refer to the same process: the transfer of a DNA fragment of interest from one organism to a self-replicating genetic element such as a bacterial plasmid (bacteria are the most often used host cells, but yeast and mammalian cells are also used). The DNA of interest propagates in the foreign host cell. This technology has been around since the 1970s and is a common practice in molecular biology labs today. Recombinant DNA technology is important for learning about other related technologies, such as gene therapy, genetic engineering of organisms, and sequencing genomes.

Stargate References

1.14 "Hathor"

Hathor rapes Daniel for his DNA

Hathor's Goa'uld larvae

Hathor's larvae perish

The Goa'uld queen named Hathor, living in a female human host, extracted DNA, what she referred to as "the code of life," from Daniel Jackson in order to produce Goa'uld larvae which would be compatible with their future human hosts. She obtained Daniel's DNA through forced sexual intercourse and thus gained access to the genetic information encoded in his sperm cells.

Sperm cells were used by the Human Genome Project (HGP) to sequence human DNA. According to the documentation from this project, it is much easier technically to prepare DNA cleanly from sperm than from other cell types because of the much higher ratio of DNA to protein in sperm and the much smaller volume in which purifications can be done. Using sperm provides all of the chromosomes for study, including equal numbers of sperm with the X (female) or Y (male) sex chromosomes. However, HGP scientists also used white cells from the blood of female donors so as to include female-originated samples.

In her reproductive process, Hathor combined portions of Daniel's DNA into her offspring. The exact method is not known, but could be considered a form of gene splicing. She may have used one sequence of his DNA and duplicated, or cloned, it to produce her treated offspring, similar to the process of recombinant DNA technology of today, also called DNA cloning. The larvae, however, had mostly Goa'uld genetic materials. Daniel's sperm did not fertilize eggs, such as is the case in the human reproductive process. According to the Tok'ra named Malek, in the episode, 6.10 "Cure", Goa'uld reproduction is asexual (without the production or union of two kinds of germ cells).

Hathor's goal to create larvae which would not be rejected by a human host is similar to that of therapeutic cloning of today. The creation of genetically-modified pigs from which organs suitable for human transplants could be harvested is a potential of this form of cloning. The transplant of organs from animals to human is called xenotransplantation. Pigs have been cloned more successfully than primates, even though primates are closer to humans genetically-speaking. Scientists create something called a "knock-out" pig wherein they inactivate the genes that cause the human immune system to reject an implanted pig organ. The genes are knocked out in individual cells, which are then used to create clones from which organs can be harvested. In 2002, a British biotechnology company reported that it was the first to produce "double knock-out" pigs that have been genetically engineered to lack both copies of a gene involved in transplant rejection. The research is still ongoing.

All of the larvae that Hathor produced at the SGC base were destroyed by fire. Dr. Fraiser attempted to get DNA samples of their remains. Daniel informed her that some of the DNA would be his. This clue to the Goa'uld's genetic make-up was very important. If she was able to obtain a complete sample of the larval DNA, Dr. Fraiser might have been able to isolate the section of the DNA which was Daniel's and thus found which sequence was responsible for rejection and then an alternate gene therapy could have been devised which could have enabled a human host to reject a symbiote from his body or created genetic changes in a human so that a symbiote could not blend with him (such as those of Aris Boch's people, in the episode, 3.07 "Deadman Switch"). Scientists of today have conducted research in using gene therapy to rewrite a subject's DNA in order to treat a problem, such as Alzheimer's.

Even though Hathor's larvae produced using Daniel's DNA all perished, it might have been possible for Hathor to have stored the necessary DNA fragments from Daniel's sperm in order to produce more larvae later. We are not made aware if she did, in fact, produce more larvae with Daniel's "code of life" after she escaped to Chulak or before she died in the episode, 3.01 "Into the Fire."

1.19 "Tin Man"

Daniel and his android clone

Teal'c's android clone being created

Jack's injured android clone

Totally within the realm of science fiction, the creation of SG-1's android doubles, or clones, was executed quite easily by Harlan of the planet Altair (P3X-989). These clones were produced by copying the likeness of each team members' physical form into a mechanical body and then copying their consciousness—memories, behavior patterns, and feelings—in the android body much like artificial intelligence. Harlan also augmented each clone with the knowledge of the underground power station which sustained them, and with the ability to compute and think faster. Their bodies were also stronger and able to endure stress, such as jumping down over twenty feet without breaking anything. The androids were also capable of existing for thousands of years if they maintained their power source, their only form of nourishment.

These androids are not clones by the classical definition because they are not biological replicas. However, to the androids themselves, their bodies felt to them as if they were still human, but "better." Their type of clone comes down low in the list of definitions of clone, but is there, nonetheless: "one that appears to be a copy of an original form."

Because these clones did not bleed when their skin was injured, it is probably reasonable to assume that there were no biological aspects of their bodies whatsoever, and that their skin was artificial. However, in today's cloning technology, scientists have taken skin cells and grown tissue, and even small forms of organs, for cows. The same therapeutic cloning can be done for humans through the use of stem cells. Research is still ongoing, but scientists hope that this leads to treating often fatal diseases by growing replacement tissue and organs without the side effect of rejection.

When the android clones went home to the SGC, Dr. Fraiser was not able to tell that they were mechanical until she listened to Jack's android's chest and found no heartbeat. Up until that moment, she might have already tested his pupils with her light pen, an instrument she has been seen using first during physical examinations, and seen nothing which would have indicated that he wasn't human. It is possible that Harlan's machine created biological organs, including eyes and tongues. It is highly doubtful, however, that these androids had any biological aspects to them because of the thousand-year lifespan, unless Harlan's machine was somehow able to stop the aging process.

The android clones of SG-1 all perished in the episode, 4.21 "Double Jeopardy."

2.20 "Show and Tell"

Genetically engineered Charlie

Cloning was most likely involved in the production of the genetically-engineered human boy named Charlie, created by a member of the alien race called the Reetou. The Reetou are basically a bug-like intelligent life form and far from being human. They also live 180 degrees out of phase with humans. They were advanced enough, however, to create a human being in the laboratory. This technology is so far beyond our current abilities that it is hard to imagine how a human boy could have grown and developed outside the uterus of a living genetically-compatible surrogate mother, such as was the case in the creation of Dolly through reproductive cloning.

The Reetou genetic engineer which created Charlie, affectionately called "Mother" by him, had to not only know the exact DNA sequence of human beings, but also other factors which scientists refer to as the building blocks of life, such as amino acids and proteins, and the nurturing environment of the womb. We are so far from that aspect of creating life solely from DNA that Mother's method of cloning is still science fiction. In other words, Mother could not have created Charlie solely from a single strand of human DNA.

We can make certain assumptions, however, that she might have used a technique similar to our "embryo cloning" in which a stem cell is stimulated to divide, thus making the single cell into a two-cell embryo, and then she would have taken that process further by allowing the embryo to develop into a human. She would have needed something beyond the DNA itself to start the process, such as having an actual stem cell.

According to Dr. Fraiser, Charlie was not put together accurately because his organs were beginning to fail. Charlie said that he was created quickly, indicating that his rate of cell division must have been increased substantially. Mother had to do this in order for him to fulfill his mission sooner than she had originally anticipated. If Charlie had been allowed to develop at a slower pace, his health may have been vastly improved. Mother also modified his genetic material so that he would be able to see and communicate with her in her phase as well.

Although we currently have the technology to create a human being through cloning today, the actual ethics of doing so is still of major debate. There have been claims made by scientists all over the world that they have successfully cloned human beings and that these clones' surrogate mothers have delivered them after a normal pregnancy. These scientists have not, however, revealed the identities of these alleged clones, so it is still debatable as to the truth of their statements. These clones, if they exist, however, could have only been produced through reproductive cloning.

Charlie was an individual, nonetheless, who had life and the right to live it. SG-1 did not feel that it was right for Mother to have created such a life as if it were only for communication purposes and then allow it to die so horribly. The Tok'ra Jacob/Selmak offered an alternative: Charlie could become a Tok'ra host and the symbiote would heal and correct his failing body. Charlie went with the Tok'ra, but further information about his life has not been revealed.

Episodes

• 1.14 "Hathor"
• 1.19 "Tin Man"
• 2.20 "Show And Tell"
• 3.01 "Into The Fire Part 2"
• 3.07 "Deadman Switch"
• 4.21 "Double Jeopardy"
• 6.10 "Cure"

Related Characters

• Col. Jack O'Neill
• Dr. Daniel Jackson
• Capt./Maj. Samantha Carter
• Teal'c
• Dr. Janet Fraiser
• Charlie
• Harlan
• Hathor
• Jacob Carter/Selmak
• Malek

Related Articles

• Goa'uld
• Reetou
• Symbiote
• Tok'ra

Further Reading

• The Gene School
• Human Genome Project: Genome Sequencing Fact Sheet
• Human Genome Project: Cloning Fact Sheet
• "Children's Hospital Boston Researchers Use Therapeutic Cloning to Create Functional Tissue in Cows"
• American Society of Gene Therapy
• The President's Council on Bioethics: Human Cloning FAQ

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--DeeKayP 14:09, 2 Oct 2004 (PDT)