By Jemima Frame
Genetic modification (GM) is now a common and easily accessible tool used by many different industries, with 1.9 million square kilometres growing GM crops in 2017 (an area equivalent to the size of Mexico!). 100 years ago, however, we had not yet created this tool (Pilcher, 2020) and after successfully accomplishing domestication and selective breeding, GM was to be the next noteworthy milestone in altering the evolutionary process. In the 1920s a German schoolteacher decided to try to produce a red canary, a process which ultimately ended in the first transgenic animal being created.
Canaries were originally green, but after centuries of selective breeding various mutant coloured canaries, including white, yellow and orange have been created. The one coloured canary no one had ever managed to produce? The red canary. In the 1920’s Hans Duncker decided to try, hypothesising that the only way to produce a red canary would be to take the ‘red genes’ from another bird species, the red siskin, and place them into canaries (Pilcher, 2020). Whilst today it may seem fairly simple to add new genes into a genome, 100 years ago this was verging on ground-breaking territory. Duncker’s plan to achieve this was to use breeding to first flood the canary genome with red siskin DNA, then refine this breeding so that only a trace of the siskin’s DNA remained; the ‘red gene’. The first stage of Duncker’s plan was to mate a male red siskin with a yellow canary, producing a hybrid. Duncker had hoped that the hybrids would have red feathers, taken from the red siskin’s genome. Stage 2 was to breed these hybrids together, which should create offspring with varying shades of red feathers. Finally, these red hybrid offsprings would be bred with a canary, hopefully keeping the red genes concentrated but discarding other unnecessary siskin genes (Birkhead, 2003).
Stage 1 of Duncker’s plan was successful and produced coppery offspring. At stage 2, however, he quickly ran into problems. The hybrids refused to breed with each other, leading him to the realisation that the females had no internal reproductive organs; they were infertile. Thankfully the male offspring were still fertile, so Duncker decided to skip stage 2 and breed the male offspring directly back to the yellow canaries. Yellow feathers are a recessive phenotype, therefore he expected three-quarters of the offspring to be red, and one-quarter to be yellow. Unfortunately, this was not the outcome, and all offspring had the same coppery coloured feathers as their fathers. Although these birds did have a different colour to a typical canary, they did not have the vibrancy of the red siskin feathers. After this failure Duncker gave up, leaving a team of international bird breeders to complete this task. Once again, these breeders mated the copper male hybrids with yellow canaries, but this time resulting in orange offsprings! These orange offspring were then bred back to the coppery offspring, resulting in an even deeper orange colour.
The final part of the process to create a red canary was solved by a physiologist called Charles Bennett. He realised that genetics by itself could not produce a red canary. He had noticed that the vibrant colour of red siskins sometimes faded when kept in captivity and hypothesised that something must be missing from their diet. Bennet used his knowledge of ‘carotenemia’ – a condition discovered when four women consumed 2kg of raw carrot every week for seven months and turned bright orange – to reason that diet could also change skin and feather colours. He also believed that red and yellow were not two discrete colours encoded in the genotype, they were two shades of the same hue, and that if a bird had yellow or orange feathers, they had the potential to have red feathers as well. Bennet decided to test this theory by feeding some of the orange canaries’ carrots and, bizarrely, after the birds had moulted, the feathers that re-grew were a rich, vibrant red! Bennet had discovered that both the genetic makeup and the diet of the canary was important (Pilcher, 2020). Feeding carrots to a yellow natural canary would have no effect as they do not have the genetic predisposition to react to them. On the other hand, transgenic canaries containing DNA from the red siskin can be induced to turn red by feeding them carrots.
In 2016, geneticists were able to pinpoint the gene that allowed transgenic canaries to turn red. The gene, called CYP2J19, encodes ketolase, an enzyme, that converts carotenoid compounds, found in carrots, into red chemicals called ketocarotenoids. Red siskins have a mutated version of this gene which causes it to be more active, explaining the vibrant red colour of the species. This mutation causes a massive increase in the production of ketocarotenoids therefore allowing the feathers of a transgenic canary to become bright red when the canary is fed carrots (Koch, 2016).
The creation of the red canary was ground-breaking; it was the first transgenic animal to be created, and the way it was created was through an amazingly low-tech approach composed of breeding and carrots. Since this discovery, genetic modification has progressed a lot and advances are still being made to this day. Animals are being altered to yield new medicines and materials, and crops are being modified to become bigger and stay ripe for longer. This technology is now used for many things, from creating designer pets to helping understand and fight diseases. There is no doubt that genetic modification is one of the most powerful technologies ever developed, and the red canary was one of the first subjects on which this technology was tested.
Pilcher, H. (2020) Life Changing; How Humans are Altering Life on Earth. London, Bloomsbury Sigma.
Birkhead, T. (2003) A brand-new bird: how two amateur scientists created the first genetically engineered animal. New York, Basic Books.
Koch, R. E., McGraw, K. J. & Hill, G. E. (2016) Effects of diet on plumage coloration and carotenoid deposition in red and yellow domestic canaries (Serinus canaria). The Wilson Journal of Ornithology. 128 (2), 328-333. Available from: doi: 10.1676/wils-128-02-328-333.1.