For the first time, scientists have genetically engineered virgin births

In an unprecedented scientific breakthrough, researchers at the University of Cambridge have revealed the first-ever instance of genetically engineering virgin birth, also known as parthenogenesis, in an organism that typically reproduces sexually. 

The study was focused on the fruit fly Drosophila melanogaster. The researchers demonstrated that the induced ability for parthenogenesis can be passed down through subsequent generations of female flies.

Most animals rely on sexual reproduction, a process that involves fertilization of a female’s egg by a male’s sperm. By contrast, parthenogenesis allows an egg to evolve into an embryo without the need for sperm. This effectively eliminates the necessity for males in the reproductive equation. 

Genetic engineering 

Dr. Alexis Sperling, a researcher at the University of Cambridge and the first author of the paper, explained the breakthrough: “We’re the first to show that you can engineer virgin births to happen in an animal – it was very exciting to see a virgin fly produce an embryo able to develop to adulthood, and then repeat the process.” 

“In our genetically manipulated flies, the females waited to find a male for half their lives – about 40 days – but then gave up and proceeded to have a virgin birth.”

The research, published in the journal Current Biology, highlights how only one to two percent of the second-generation female flies with the capability for parthenogenesis managed to produce offspring. This only occurred in the absence of males. If male flies were present, the females resorted to conventional sexual reproduction.

This ability to switch to parthenogenesis could act as a strategic survival tactic. For instance, a solitary generation of virgin births could potentially keep the species alive and flourishing.

Conducting the virgin birth study 

To investigate, the research team initially sequenced the genomes of two strains of Drosophila mercatorum, a separate species of fruit fly. One strain was dependent on males for reproduction, while the other exclusively used parthenogenesis. 

Through this process, the researchers were able to identify the genes that were activated or deactivated during fatherless reproduction.

Armed with the knowledge of potential virgin birth genes in Drosophila mercatorum, the team manipulated what they believed to be corresponding genes in Drosophila melanogaster. The experiment was successful – Drosophila melanogaster gained the ability to reproduce through parthenogenesis.

This monumental research spanned six years and involved more than 220,000 virgin fruit flies. One of the key factors contributing to this discovery was the researchers’ choice to use Drosophila melanogaster. This species of fruit fly has been a model organism in genetic research for over a century due to its well-understood genes.

Virgin birth among insects

Dr. Sperling, who conducted this research in the Department of Genetics, has now shifted to the Cambridge Crop Science Centre, where she will focus on crop pests. She aims to delve deeper into the increasing frequency of virgin birth among insects, particularly in pest species.

“If there’s continued selection pressure for virgin births in insect pests, which there seems to be, it will eventually lead to them reproducing only in this way. It could become a real problem for agriculture because females produce only females, so their ability to spread doubles,” said Dr. Sperling.

While virgin birth is a natural occurrence among certain egg-laying animals, such as birds, lizards, and snakes, it is relatively rare among animals that generally reproduce sexually. Zoo animals, particularly females isolated for extended periods with little hope of finding a mate, often exhibit parthenogenesis.

This research not only redefines the boundaries of our understanding of reproduction but also raises intriguing questions about the potential consequences of such genetic manipulation in the future.

More about virgin birth

Parthenogenesis, commonly referred to as “virgin birth,” is a form of asexual reproduction where growth and development of embryos occur without fertilization. The term comes from the Greek “parthenos,” meaning “virgin,” and “genesis,” meaning “origin.”

While parthenogenesis is quite rare in mammals, certain animal groups exhibit it more frequently. These include insects, fish, amphibians, reptiles, and birds. 

The offspring produced through this method are usually female and genetically similar to the mother, but they are not exact clones. This is because the genetic material comes entirely from the mother, without any contribution from a male.

Types of parthenogenesis 

There are several types of parthenogenesis. In “automixis,” the egg cells undergo a kind of self-fertilization. Here, meiosis, the process that halves the number of chromosomes in the egg cell, is followed by a duplication or fusion of the genetic material, which restores the full complement of chromosomes. 

In “apomixis,” on the other hand, the egg cell doesn’t undergo meiosis, which means the offspring has the same genetic makeup as the mother.

Survival strategy 

The biological benefit of parthenogenesis is primarily related to survival. If females in a population are unable to find males to mate with, parthenogenesis allows the continuation of the species. This can occur in environments with low population density or situations where isolation affects the females.

However, sexual reproduction still offers the advantage of genetic diversity, which is critical for the long-term survival and adaptability of a species.

New realm of possibilities 

The discovery of the ability to induce parthenogenesis artificially, such as in the case of the fruit flies mentioned earlier, opens a new realm of possibilities for scientific research. 

For instance, understanding the genetics behind parthenogenesis might lead to advances in fertility treatments. But it also poses important ethical and ecological considerations, given the potential consequences of manipulating reproduction in this way.

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