The idea of cloning an organism from a single strand of hair is a common concept in fiction, yet the reality is far more intricate than popular portrayals suggest. Cloning, in the context of creating a genetically identical copy of a whole organism, relies on a complex laboratory procedure requiring specific biological material. The question of whether hair can provide this material is answered by understanding the biological requirements of this advanced technique.
The Basics of Somatic Cell Nuclear Transfer
The established method for reproductive cloning in mammals is called Somatic Cell Nuclear Transfer (SCNT). This procedure requires two fundamental components: a somatic cell and an egg cell. A somatic cell is any cell from the body that is not a sperm or egg cell, such as a skin, liver, or muscle cell, and it must contain a full, intact set of DNA within its nucleus.
The process begins by taking an unfertilized egg cell and removing its nucleus, a process known as enucleation. This creates an empty vessel containing cellular machinery but lacks genetic information. Next, the nucleus containing the full DNA from the donor somatic cell is inserted into this enucleated egg.
Scientists then use an electrical pulse or chemical treatment to stimulate the newly formed cell to begin dividing as if it were a fertilized zygote. The egg’s cytoplasm contains factors that reprogram the mature somatic cell nucleus, reverting it to an embryonic state capable of developing into a complete organism. If this initial division is successful, the embryo can be transferred to a surrogate mother.
Biological Components of Hair
To determine if hair can be used for SCNT, its structure must be examined for somatic cells. A hair strand consists of two main parts: the shaft and the follicle, or root. The visible hair shaft is composed almost entirely of dead cells packed with the protein keratin.
These dead cells have highly degraded nuclei and are not a viable source of intact nuclear DNA required for cloning. The only location containing living cells with complete, functional nuclei is the hair follicle, which is the structure anchored beneath the skin. Specifically, the epithelial cells surrounding the root, often referred to as the root tag when the hair is plucked, are the only cells that could serve as the somatic cell donor.
Challenges of Using Hair Follicle Cells
While the hair follicle does contain the necessary living somatic cells, using them for SCNT presents challenges. The primary challenge is obtaining a sufficient number of cells that are viable and structurally undamaged. Once a hair is plucked, the fragile cells of the root tag are immediately exposed to an environment that leads to rapid cell death and degradation.
Even if a viable cell is successfully isolated, preparing it for SCNT requires that the cell be cultured and multiplied in a laboratory setting. Hair follicle cells, such as the dermal papilla cells, are difficult to maintain in culture while preserving their specialized function. They often lose their necessary biological properties when grown in a standard two-dimensional dish, making them unsuitable for the delicate reprogramming step of SCNT.
Furthermore, the quantity and quality of the nuclear DNA are often compromised. Hair samples yield a very small amount of nuclear DNA, which is insufficient for the demands of the SCNT procedure. Environmental exposure and keratinization in the follicle increase the likelihood of DNA damage or fragmentation, which severely reduces the chances of successful nuclear reprogramming.
Practical Status and Alternative Methods
In practice, the technical complexity, low yield, and poor viability of hair follicle cells render them an impractical choice for SCNT. While DNA can be extracted from a hair root for genetic analysis, like in forensics, the requirement for a living, intact, and easily culturable cell for cloning is a much higher standard that hair cells generally fail to meet. The inherent difficulty results in an extremely low, almost negligible, success rate. For this reason, researchers rely on alternative cell types that are easier to collect and maintain.
Preferred somatic cells include skin fibroblasts, which are readily available and easily grow in standard laboratory culture conditions. Fetal cells and cumulus cells are also frequently chosen because they are more efficient at undergoing the essential reprogramming process. Even with these more ideal cell sources, SCNT remains an inefficient process, with success rates often in the low single digits.