Cloning is a complex process that raises many ethical and scientific questions. One such question is whether cloned individuals would be able to reproduce. This article will examine what cloning is, how clones are created, whether clones can get pregnant, and the ethical implications.
What is cloning?
Cloning is the process of creating a genetically identical copy of an organism. In nature, clones occur through asexual reproduction, which involves mitosis (cell division). Many plants, bacteria, and simple animals like sea anemones can reproduce asexually.
In biotechnology, cloning refers to artificial cloning, which involves somatic cell nuclear transfer (SCNT). This is the process used to clone sheep, cats, deer, horses and other mammals. It involves taking the nucleus from a body cell of the organism to be cloned and inserting it into an egg cell that has had its nucleus removed. This egg is then stimulated to divide and develop into an embryo, which is implanted into a surrogate mother. The resulting offspring is a genetic copy of the original organism.
How are clones created through somatic cell nuclear transfer?
Here are the key steps involved in somatic cell nuclear transfer cloning:
- Obtain a suitable egg cell, or oocyte, from a female of the species to be cloned. The egg nucleus is removed.
- Obtain a somatic cell, like a skin or blood cell, from the organism to be cloned.
- Remove the nucleus from the somatic cell.
- Insert the somatic cell nucleus into the enucleated egg cell.
- Stimulate the reconstructed egg to divide, usually with electricity or chemicals.
- Allow the embryo to develop to the blastocyst stage in culture.
- Transfer the blastocyst clone embryo into a surrogate mother’s uterus for gestation.
- Allow the clone embryo to develop normally during pregnancy, resulting in a genetically identical offspring at birth.
This complex procedure has a very low success rate. Many cloned embryos fail to properly reprogram gene expression and develop normally.
Can clones reproduce sexually?
Yes, clones created through somatic cell nuclear transfer are capable of normal sexual reproduction. Even though they originate from a single genetic source, they develop into unique individuals that are physiologically capable of producing viable sperm or eggs.
Reproductive cloning produces an organism that is genetically identical to the original animal from which the nuclear DNA was taken. However, the clone is in every other physiological way a unique individual capable of reproducing sexually. Clones go through puberty and sexual maturation like non-clones of their species.
Evidence that clones can reproduce
There is evidence from animal studies that clones are fertile and can reproduce sexually:
- In 2004, Japanese researchers generated the first cloned bull from a somatic cell. This bull was mated and produced normal calves, demonstrating the fertility of cloned male animals.
- In 2007, transgenic sheep named Polly and Molly were cloned using somatic cell nuclear transfer. Polly gave birth to two lambs conceived naturally, proving cloned female fertility.
- The famous cloned sheep Dolly was bred conventionally and produced six lambs over the course of her life, all created through natural mating and reproduction.
- Cloned horses, such as the famous stallion Gemini, have successfully mated and reproduced after being cloned.
Additionally, the reproductive cells of clones, such as eggs and sperm, appear molecularly and functionally normal. There is no evidence that cloning intrinsically impairs the gonads or reproductive capacities.
Can human clones reproduce?
There is no directly relevant evidence available about human clones and reproduction because human cloning is currently illegal throughout the world. However, based on what we know from animal studies, it is expected that human clones would be fertile unless impairments occurred during development.
Humans have been cloned at the embryonic stage for stem cell research purposes using SCNT. However, these clones were not allowed to develop into infants. The limited embryo development that did occur showed no signs of impaired reproductive system formation.
There are also no theoretical reasons why a human clone could not reproduce, provided normal gonad development. The genetic identity between clone and source should not impact sexual functioning.
Potential complications
Some potential complications that could impact a human clone’s fertility include:
- Developmental defects in reproductive organs due to incomplete nuclear reprogramming.
- Hormone deficiencies caused by abnormal endocrine system development.
- Genetic defects passed down from source that compromise fertility.
- Abnormal epigenetic gene regulation interfering with sexual maturation.
However, most defects would likely impact overall clone viability far before reaching reproductive maturity. clones surviving to adulthood would likely have normal sexual functioning barring non-genetic issues.
Ethical concerns over cloned reproduction
The ability for clones to reproduce raises some ethical issues:
- Inbreeding complications: Reproduction between clones may increase issues associated with inbreeding since clones are genetically identical.
- Identity issues: Clones may struggle with identity if their children are essentially delayed genetic twins.
- Restricted gene pool: Extensive cloning within a population restricts genetic diversity.
- Violation of clone autonomy: Clones deserve the freedom to choose whether to reproduce.
- Dignity of offspring: The nature of cloned parents may unfairly impact the social dignity afforded to their sexual offspring.
However, clones reproducing does not differ ethically from cases of naturally occurring identical twins reproducing. And most major ethicists and scientists agree human cloning itself raises far greater moral concerns than those associated with clone fertility.
Conclusions
Based on animal studies, clones created through somatic cell nuclear transfer are expected to be capable of normal, functional sexual reproduction. Both male and female clones across a variety of species have mated and produced viable offspring. Although there are some risks of developmental defects, clones that reach maturity would likely have normal reproductive abilities.
While human clones remain illegal for now, they are theoretically expected to be fertile. However, serious ethical questions surrounding identity, dignity, autonomy, and the welfare of offspring would need to be addressed if human clones were allowed to reproduce.
