Geneticists were able to edit the embryo of a bull so that his posterity was dominated by males, what has been achieved using a targeted insertion of the transgene. The SRY gene was inserted into chromosome 17, which should get at least half of the embryos with the XX genotype to develop in the male way. The report was presented July 23 at a meeting of the American society of animal science.
Modern farming almost everywhere away from the content of the floor stud with natural populations, part of which goes on meat, and the part producing milk. Instead, there are separate industries, the two largest of which meat and dairy. The animals they breed almost exclusively artificial, and so the sexual balance born calves would be beneficial to subdue a man. For the meat industry is more valuable for the bulls because they are more efficient in gaining weight when consuming the same calories, but their meat is tastier and can be used for the manufacture of expensive steaks. However, by nature the ratio of male and female progeny of a cow is approximately equal.
Most mammals normally males have sex chromosomes XY and females XX. Strictly speaking, it’s not the mere existence of Y and the presence of SRY gene responsible for male development. If SRY is on any other chromosome, the embryo will become a male. For example, a similar pattern is observed in people with the syndrome de La Chapelle, which have the female genotype is XX, but the male body that is considered to be a pathology because it inevitably leads to infertility. Details about why gender is not always determined by chromosomes, read the material “Easy to be a man”.
Joey Owen (Joey Owen) from the University of California and her colleagues decided to seek a more favorable balance of sexual cows. First they tried to transplant the SRY gene in the X chromosome, which would lead to offspring, consisting only of males. After this failed, the researchers chose a different chromosome, 17 — the authors argue that it is the most safe and reliable option.
Generally, for targeted insertion of the transgene uses a process called homologous recombination in somatic cells followed by cloning — in other words, conduct operations not by the embryo, and cell culture, the core of which is then implanted into the egg. Here, scientists injected reagents CRISPR/Cas9 and donor HMEJ-vectors directly into the zygote (first stage embryo) after 6 hours after fertilization.
As a result, the Cosmo bull, the progeny of which, according to the calculations of the authors of the study, should be approximately 75 percent of bulls. This is due to the fact that when crossed with the usual cows, the SRY gene will be inherited not every time, but only in half of the cases. As a result of the offspring will be half natural bulls with genotype XY, and 25 percent will carry the XX genotype, but have the body of males. I should add that neither Cosmo nor his immediate descendants would not be in the butcher shop: the rules for genetically modified meat are very strict, and it is released to the market only after numerous inspections and certifications.
Products from GMOs do not carry any harm, but have many advantages. For example, thanks to her calves become resistant to tuberculosis, lost his horns, and rice, who is not afraid of pests, has not lost in productivity.