In short: Cloning is the creation of a living being whose genes all come from a single cell of an adult. Many animals have been cloned since Dolly the sheep, but no cloned human has ever been proven to exist, and reproductive human cloning is banned in most countries. What holds most promise for patients is research on making eggs and sperm in the laboratory, which is still experimental.

Human Cloning Explained: Myths, Facts, and What It Means for Fertility Treatment

In brief: Cloning means making a new organism whose genes come from one single adult cell. Many animals have been cloned since Dolly the sheep, but no cloned human has ever been proven to exist, and reproductive cloning of humans is banned in most countries and forbidden by Islamic jurisprudence. The most promising spin-off for patients is research on making eggs and sperm from other cells in the laboratory, which is still experimental.

For a look at where this work takes place, visit our tour of the IVF laboratory.

What is cloning?

Imagine a copy of yourself, like an identical twin, made from one of your own body cells. In simple terms, cloning means copying a cell, a part of a cell or its DNA, so that the copy carries the same genes as the original. There are three types:

DNA cloning: copying a piece of DNA inside bacteria in the laboratory. It is used every day in research and to make medicines such as insulin.
Therapeutic cloning: making an early embryo from a patient’s cell in order to obtain stem cells for research or treatment. It is not used to create a baby.
Reproductive cloning: making a whole animal with the same nuclear DNA as another animal. This is the kind of cloning most people mean.

How is reproductive cloning done?

The method is called somatic cell nuclear transfer. “Somatic” means an ordinary body cell, not an egg or a sperm.

The nucleus, which contains all 46 chromosomes in humans, is taken from a body cell of the animal to be copied.
The nucleus of an egg from a second animal is removed.
The body-cell nucleus is placed inside the empty egg. A small electric pulse or chemicals make the egg start dividing as if it had been fertilised.
The embryo is transferred to the womb of a surrogate mother.

A simpler method, artificial embryo twinning, splits a very early embryo into separate cells in the laboratory, as happens naturally with identical twins. Each cell can grow into an embryo with the same genes.

The natural process is described in its own article on fertilization and conception.

How is cloning different from natural conception?

In natural conception, the sperm brings 23 chromosomes and the egg brings 23. The baby has 46 chromosomes, half from each parent, and is genetically different from both. In cloning, all 46 chromosomes come from the one body cell, so the new animal has the same nuclear genes as the donor.

The treatments currently offered to couples are outlined in our overview of infertility treatment for men and women.

A clone is still not a perfect copy. The egg’s mitochondria, the cell’s energy stores, have their own small amount of DNA, which comes from the egg donor. Genes are also switched on and off differently, and each animal grows up in its own environment. A clone is more like an identical twin born years later than a photocopy.

A short history

1952: first nuclear transfer in frogs (Briggs and King). John Gurdon later cloned frogs from specialised cells and shared the 2012 Nobel Prize.
1996: Dolly the sheep, the first mammal cloned from an adult cell, was born on 5 July 1996 at the Roslin Institute in Scotland and announced in February 1997.
Since then: mice, cows, goats, pigs, rabbits, cats (2001), a horse (2003), a dog (2005), a camel in Dubai (2009), and monkeys in China (2018). Camels, horses and pets are now cloned commercially in some countries.
Humans: no cloned baby has ever been proven. Claims made in 2002 were never verified. In 2013, scientists used nuclear transfer to make human embryonic stem cells for research only.

Did Dolly age early?

Dolly was put down in February 2003, aged 6½, because of a lung tumour and arthritis. The tumour was caused by a virus that also affects sheep kept indoors that are not cloned. In 2016, researchers reported that four clones made from the same cells as Dolly had reached old age in good health.

What are the risks of cloning?

It is very inefficient. Only about 1 to 5 in every 100 cloned embryos becomes a live-born animal, even today.
Problems before and around birth. Many pregnancies are lost. Some calves and lambs are born very large (“large offspring syndrome”) or with problems of the placenta, heart, lungs or kidneys.
Reprogramming errors. The adult nucleus has to be “reset” to behave like a new embryo, and this often goes wrong.
Long-term health. Clones that survive the first weeks often live fairly normal lives, but long-term effects are still being studied.

Should humans be cloned?

The scientific and medical community agrees that human reproductive cloning would be unsafe and unethical. The risk of losing the pregnancy or of a baby being born with serious problems is far too high. It also raises deep questions about identity and family.

The United Nations declaration of 2005 and the laws of most countries ban it.
The International Islamic Fiqh Academy ruled human reproductive cloning forbidden in 1997.
Research on cloned human embryos is strictly regulated, where it is allowed at all.

Can cloning research help infertile couples?

Cloning itself is not a treatment for infertility. Research that grew out of it, however, may one day help couples with no eggs or no sperm.

Stem cells made from adult cells (iPS cells). Since 2006, scientists can turn skin or blood cells back into stem cells without using an embryo. This has largely replaced therapeutic cloning and earned a Nobel Prize in 2012.
Eggs and sperm made in the laboratory (in vitro gametogenesis). In mice, researchers have made healthy eggs and sperm from stem cells, and the resulting mice had pups. In humans, this is only at an early laboratory stage.
Halving the chromosomes of a body cell (“haploidisation” or “mitomeiosis”). The idea is to reduce a body cell’s 46 chromosomes to 23 so it can act like an egg or a sperm. In 2025, researchers in Oregon made human eggs from skin cells this way and fertilised them. A few embryos formed, but most had abnormal chromosomes. It will be many years, if ever, before this can be used in patients.
Protecting fertility before cancer treatment. Boys who need chemotherapy before puberty can have a small piece of testicular tissue frozen, in the hope that stem cells from it can later be put back to make sperm. This works in animals and is still experimental in humans. Women and girls can freeze eggs, embryos or ovarian tissue.

Science moves step by step, and ideas that seem impossible today can become treatments tomorrow. At

Dr Najeeb Layyous’s clinic, we follow new research closely and offer our patients only treatments that are proven and safe. If you have questions about your own fertility, we are happy to talk them through with you.

Present and futuristic developments in fertility treatment | Fertility preservation in cancer patients

Dr Najeeb Layyous F.R.C.O.G

Consultant Obstetrician, Gynecologist and Infertility Specialist