Latest news with #chromosomes
France 24
5 days ago
- Science
- France 24
Scientists find surprising sex reversal in Australian birds
A study of five common Australian species, including kookaburras, magpies and lorikeets, found around six percent of birds had the chromosomes of one sex but the reproductive organs of another. The findings indicated a surprisingly high number of birds had reversed their sex after birth, said researchers from the University of the Sunshine Coast. "This indicates that sex determination in wild birds is more fluid than we thought, and can persist into adulthood," said study co-author Dominique Potvin. The study performed DNA tests on almost 500 birds. The overwhelming majority of sex reversals involved genetically female birds growing male gonads. "We also discovered a genetically male kookaburra who was reproductively active with large follicles and a distended oviduct, indicating recent egg production," said Potvin. Sex reversal is well known in certain species of reptile and fish but is thought to be rare in wild birds and mammals. Scientists have documented how pollutants and even warm temperatures can trigger sex reversal in frogs. The cause of sex reversal in wild birds was not clear, the University of the Sunshine Coast study said. But it could be due to environmental factors, such as hormone-disrupting chemicals building up in wild areas. "Understanding how and why sex reversal occurs is vital for conservation and for improving the accuracy of bird research," added Potvin. The study was published this week in peer-reviewed journal Biology Letters.
Yahoo
09-08-2025
- Science
- Yahoo
Ancient viral DNA may play a key role in early human development, new study suggests
The human genome is made up of 23 pairs of chromosomes, the biological blueprints that make humans … well, human. But it turns out that some of our DNA — about 8% — are the remnants of ancient viruses that embedded themselves into our genetic code over the course of human evolution. These ancient viruses lie in sections of our DNA called transposable elements, or TEs, also known as 'jumping genes' due to their ability to copy and paste themselves throughout the genome. TEs, which account for nearly half of our genetic material, were once waved off as 'junk' DNA, sequences that appear to have no biological function. Now, a new study offers support for the hypothesis that these ancient viral remnants play a key role in the early stages of human development and may have been implicated in our evolution. By sequencing TEs, an international team of researchers identified hidden patterns that could be crucial for gene regulation, the process of turning genes on and off. The findings were published July 18 in the journal Science Advances. 'Our genome was sequenced long ago, but the function of many of its parts remain unknown,' study coauthor Dr. Fumitaka Inoue, an associate professor in functional genomics at Kyoto University in Japan, said in a statement. 'Transposable elements are thought to play important roles in genome evolution, and their significance is expected to become clearer as research continues to advance.' There are many benefits to studying how TEs activate gene expression. It could help scientists understand the role that the sequences play in human evolution, reveal possible links between TEs and human diseases, or teach researchers how to target functional TEs in gene therapy, said lead researcher Dr. Xun Chen, a computational biologist and principal investigator at Shanghai Institute of Immunity and Infection of the Chinese Academy of Sciences. With more research, 'we hope to uncover how TEs, particularly ERVs (endogenous retroviruses, or ancient viral DNA), make us human,' Chen added in an email. Embedded ancient viral DNA When our primate ancestors were infected with viruses, sequences of viral genetic information would replicate and insert themselves in various locations in the host's chromosomes. 'Ancient viruses are effective in invading our ancestral genomes, and their remnants become a big part of our genome. Our genome has developed numerous mechanisms to control these ancient viruses, and to eliminate their potential detrimental effects,' said Dr. Lin He, a molecular biologist and the Thomas and Stacey Siebel Distinguished Chair professor in stem cell research at the University of California, Berkeley, in an email. For the most part, these ancient viruses are inactive and are not a cause of concern, but in recent years, research has shown that some of the transposable elements may play important roles in human diseases. A July 2024 study explored the possibility of silencing certain TEs to make cancer treatment more effective. 'Over the course of evolution, some viruses are degenerated or eliminated, some are largely repressed in expression in normal development and physiology, and some are domesticated to serve the human genome,' said He, who was not involved with the new study. 'While perceived as solely harmful, some ancient viruses can become part of us, providing raw materials for genome innovation.' But because of their repetitive nature, transposable elements are notoriously difficult to study and organize. While TE sequences are categorized into families and subfamilies based on their function and similarity, many have been poorly documented and classified, 'which could significantly impact their evolutionary and functional analyses,' Chen said. Ancient viral impact on human development and evolution The new study focused on a group of TE sequences called MER11 found within primate genomes. By using a new classification system as well as testing the DNA's gene activity, researchers identified four previously undiscovered subfamilies. The most recently integrated sequence, named MER11_G4, was found to have a strong ability to activate gene expression in human stem cells and early-stage neural cells. The finding indicates that this TE subfamily plays a role in early human development and can 'dramatically influence how genes respond to developmental signals or environmental cues,' according to a statement from Kyoto University. The research also suggests that viral TEs had a part in shaping human evolution. By tracing the way the DNA has changed over time, the researchers found that the subfamily had evolved differently within the genomes of different animals, contributing to the biological evolution that resulted in humans, chimpanzees and macaques. 'To understand the evolution of our genome is one way to understand what makes humans unique,' said He. 'It will empower us with tools to understand human biology, human genetic diseases, and human evolution.' Exactly how these TEs were implicated in the evolutionary process is still unclear, Chen said. It is also possible that other TEs that have yet to be identified played distinct roles in the evolutionary process of primates, he added. 'The study offers new insights and potential leverage points for understanding the role of TEs in shaping the evolution of our genomes,' said Dr. Steve Hoffmann, a computational biologist at the Leibniz Institute on Aging in Jena, Germany, who was not involved with the study. The research also 'underscores how much more there is to learn from a type of DNA once slandered as a molecular freeloader,' he added in an email. Hoffmann was the lead researcher of a scientific paper that first documented the nearly complete genome map of the Greenland shark, the longest-living vertebrate in the world that can survive until about 400 years old. The shark's genome was made up of more than 70% jumping genes, while the human genome is composed of less than 50%. While primate genomes are different from those of a shark, 'the study provides further evidence for the potential impact of TEs on genome regulation' and 'is a message with relevance for all genome researchers,' Hoffmann said. By investigating how genomes have evolved, researchers can determine which DNA sequences have remained the same, which have been lost in time and which have emerged most recently. 'Taking these sequences into account is often critical to understanding, e.g., why humans develop diseases that certain animals don't,' Hoffmann said. 'Ultimately, a deeper understanding of genome regulation can aid in the discovery of novel therapies and interventions.' Taylor Nicioli is a freelance journalist based in New York. Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. Solve the daily Crossword
Health Line
01-08-2025
- Health
- Health Line
What's the Difference Between a Gene and a Chromosome?
Genes are segments of DNA (deoxyribonucleic acid) that are located inside every human cell. The DNA inside each cell is tightly coiled in structures called chromosomes. Each chromosome contains a single thread of DNA with many different genes. The genes provide instructions for different traits, such as eye or hair color, or male or female sex. Chromosomes come in pairs. Humans have 46 chromosomes, in 23 pairs. People inherit chromosomes from their parents. A child gets one of each pair of chromosomes from their mother and one of each pair of chromosomes from their father. The term ' genetic inheritance ' is the passing down of DNA from parents to children. What is a genetic disorder? Genetic disorders, such as Down syndrome or cystic fibrosis, occur when: there's a change (mutation) in a gene on a chromosome a chromosome is missing a part (called a deletion) when genes move from one chromosome to another (called a translocation) when a cell has extra chromosomes or missing chromosomes A worldwide gene research project, called the Human Genome Project, is creating a map of all human genes and their location on chromosomes. Doctors hope to use this map to find and treat genetic disorders. What do genes and chromosomes have to do with your health? Genes are involved in almost every human trait and disease. They influence how your body responds to: certain health conditions, such as infections medications treatments for health conditions certain behaviors, such as smoking or alcohol use The more we understand how genes affect our health or are linked to disease, the earlier doctors can respond to diseases and provide more effective targeted treatments.
Yahoo
25-06-2025
- Science
- Yahoo
Study slices and dices the complex history of the modern strawberry
If you eat fruits or vegetables, how often do you think about their history? Former University of Florida post-doctoral researcher Zhen Fan did, as he traced the strawberry back over centuries. In a new paper published in the Proceedings of the National Academy of Sciences, Fan, now a faculty member at Zhejiang Agriculture and Forestry University in China, examined the ancient origins of strawberry strawberries have eight sets of chromosomes, making them what scientists call 'octoploids.' By comparison, most species, including humans, have two sets of chromosomes: they're diploids. 'The modern strawberry has about four times as much DNA as the most ancient wild strawberries,' said Vance Whitaker, a UF/IFAS professor of horticultural sciences, Fan's former supervisor and a corresponding author of the paper. 'This happened through hybridization (crossing) of up to four distinct wild species over a long time.' 'But this history and the identity of each of these ancient species have been difficult to trace because some of them went extinct long ago, and we can't study them directly,' said Whitaker, a strawberry breeder at the Gulf Coast Research and Education Center. In the new study, Fan found an approach to better trace that history and, in the process, he found that, before the modern strawberry began to form, various types of ancient species crossed with each other. 'This means that the genetic background of the modern strawberry is even more complex than we thought,' Whitaker said. 'One reason this is important is that one day, we would like to reconstruct the modern strawberry from simpler species by making the crosses ourselves, and better understanding how the strawberry formed will help us do that,' Whitaker said. 'This could help us to breed better strawberry varieties in the future that are more genetically diverse and more resistant to pests and diseases.' Strawberry is kind of the opposite of a 'purebred,' Whitaker said. 'With multiple species in its background the strawberry is fun and challenging to work with for a breeder like me,' he said. Doug and Pam Soltis, distinguished professors at the Florida Museum of Natural History and co-authors on the study, put the research into an interesting historical perspective. 'Strawberry might be the opposite of a purebred, but it is typical of the complexities we see in natural populations of plants — complicated evolutionary histories of repeated hybridization, introgression and genome doubling,' Doug Soltis said. 'Solving these problems involves dedicated research — each is a story of intrigue and investigation that puts solving any murder mystery to shame.' Added Pam Soltis: 'The methods developed for reconstructing the evolutionary history of strawberries may be useful in other crops where the ancestry is also uncertain. Polyploidy (more than two sets of chromosomes) is very common in wild plants — and occurs in other organisms as well, and I look forward to applying these methods to the study of wild polyploid species for which we know almost nothing about their evolutionary history.' This article originally appeared on Tallahassee Democrat: Study slices into the complex history of modern strawberry
