Mon. Dec 6th, 2021

None of the birds were particularly strong, but the fact that they survived beyond laying eggs is a big deal. “I think this is one of the most important studies on parthenogenesis and birds in the long run,” said Warren Booth, an evolutionary biologist at the University of Tulsa who studied the facultative parthenogenesis of snakes and was not involved in the study. He says that although sharks and ray produced through asexual reproduction have survived and even improved, it has not been seen in birds. Parthenotes born from domesticated turkeys, chickens, quails, zebra finches and pigeons almost all died before laying eggs.

Although these condors died at a young age, Booth says, “it gives us some information that perhaps in raptors, we can see healthy অথবা or at least living and somewhat effective ক্ষমতা the ability to produce parthenogen that could potentially reproduce in that population.”

Most vertebrates reproduce sexually, mixing genetic information from male and female partners to produce offspring in a new combination of genes. This arrangement has some advantages: If a fetus inherits a defective copy of a gene from one parent, the copy from another parent can compensate.

But sometimes animals, especially birds, including ancient genomes, lizards, sharks and snakes, go out of the co-male equation and reproduce asexually. Like mammals, the females of this species produce eggs through meiosis, the process by which chromosomes are separated. The fragments are divided into four individual cells, of which only one is an egg. During sexual reproduction, an ovum combines its genetic material with the sperm produced by the male. But during parthenogenesis, the egg combines with another cell instead, forming a self-fertilized egg.

Parthenates can only be one sex, although any sex depends on their species. For snakes like Boas and Python, the Parthenotes are all female: their chromosomes are XX.

Unlike humans, for birds it is not the egg, not the sperm, that indicates the sex of the fetus. For this reason, scientists use a different naming system for their chromosomes. A woman has a ZW chromosome, while a man has a ZZ. If a woman reproduces asexually, it means she can only produce a WW or ZZ embryo. But a WW in birds cannot produce an effective embryo, so all avian parthenotes who survive at the egg stage and beyond must be ZZ-male.

Typically, parthenogenesis occurs in women when no male partner is found. Theoretically, this process allows a woman to continue gene pooling until a suitable male arrives. But that’s not an ideal solution, Booth says. Since the egg is mixed with a cell that has almost identical chromosomes, there is almost no genetic diversity among the offspring. “Across most of its genome, it lacks diversity, which is why we see in most cases of pathogenesis, animals don’t work well in the long run,” he says. “They’re the most birthright you can have.”

But Damien Chapman, director of the shark and ray conservation program at the Florida Total Marine Laboratory, who identified several different parasites between sharks and ray, noted that they are more likely to have genetic defects, but that survivors may be free. A variant of some lethal genes common in a species. “They probably can’t carry them, because if they carry them, they will die because there is no one else to compensate them,” he said.

Source link

By admin

Leave a Reply

Your email address will not be published. Required fields are marked *