The size of the brain of a chimpanzee (right) is considerably smaller than that of a human brain. Probably multiple stretches of DNA help determine that, geneticists say. Science Photo Library/Corbis hide caption The size of the brain of a chimpanzee (right) is considerably smaller than that of a human brain. Probably multiple stretches of DNA help determine that, geneticists say. Scientists studying the difference between human and chimpanzee DNA have found one stretch of human DNA that can make the brains of mice grow significantly bigger. "It's likely to be one of many DNA regions that's critical for controlling how the human brain develops," says Debra Silver, a neurobiologist at Duke University Medical School. The human version of a DNA sequence called HARE5 (inserted into this mouse embryo) turned on a gene that's important for brain development. (Gene activity is stained blue.) By the end of gestation, the embryo's brain was 12 percent larger than the brain of an embryo injected with the chimpanzee version of HARE5. Silver Lab/Duke University hide caption The human version of a DNA sequence called HARE5 (inserted into this mouse embryo) turned on a gene that's important for brain development. (Gene activity is stained … Continue reading →

Single-letter genetic variations within parts of the genome once dismissed as 'junk DNA' can increase cancer risk through wormhole-like effects on far-off genes, new research shows. Researchers found that DNA sequences within 'gene deserts' -- so called because they are completely devoid of genes -- can regulate gene activity elsewhere by forming DNA loops across relatively large distances. The study, led by scientists at The Institute of Cancer Research, London, helps solve a mystery about how genetic variations in parts of the genome that don't appear to be doing very much can increase cancer risk. Researchers developed a new technique to study the looping interactions and discovered that single-letter DNA variations linked to the development of bowel cancer were found in regions of the genome involved in DNA looping. Their study, published today in Nature Communications, is the first to look comprehensively at these DNA interactions specifically in bowel cancer cells, and has implications for the study of other complex genetic diseases. It was funded by the EU, Cancer Research UK, Leukaemia & Lymphoma Research, and The Institute of Cancer Research (ICR). The researchers developed a technique called Capture Hi-C to investigate long-range physical interactions between stretches of DNA -- … Continue reading →