Genetic Clue Discovered For Why Women Outlive Men

A new study of mitochondrial DNA in fruit flies offers a number of clues that might explain why females tend to outlive males across much of the animal kingdom, including humans. Researchers from Monash University in Australia and Lancaster University in the UK, write about their work in the 2 August online issue of Current Biology. They found male fruit flies appear to have mutations in their mitochondrial DNA that affect how fast they age and how long they live. Scientists use fruit flies as models for studies in genes and aging because their biological processes are remarkably similar to that of other animals, such as humans, and with a lifespan of about a month, it doesn't take too long to investigate generational effects. Senior author Damian Dowling, a research fellow in the Monash School of Biological Sciences, told the press: "All animals possess mitochondria, and the tendency for females to outlive males is common to many different species. Our results therefore suggest that the mitochondrial mutations we have uncovered will generally cause faster male aging across the animal kingdom." "Intriguingly, these same mutations have no effects on patterns of aging in females. They only affect males," he added. Mitochondria are special subunits of cells, about the same size as bacteria, that provide the energy for life. They combine sugar and oxygen into adenosine triphosphate or ATP, molecular packets of energy that are usable by cells. Mitochondria have their own DNA that is quite separate from the cellular DNA in the nucleus of the cell. And, unlike cellular DNA, which is inherited from the sperm and egg that fuse to make the new...

Genetic Screening During Pregnancy Shows Promise

According to a study published inScience Translational Medicine, researchers at the University of Washington have successfully reconstructed the whole genome sequence of a human fetus by analyzing blood samples from the mother and saliva samples from the father. The researchers findings open up the possibility of assessing a fetus non-invasively for all single-gene disorders. Approximately 1% of newborns are born with disorders that are caused by a defect in a single gene. These "Mendelian" disorders include cystic fibrosis, Huntington's disease, and Tay-Sachs disease. In the future, the new non-invasive technique could help screen for these types of genetic mutations in the fetus without increasing the risk of miscarriage, said Jay Shendure and his team at the University of Washington. Shendure explained: "This work opens up the possibility that we will be able to scan the whole genome of the fetus for more than 3,000 single-gene disorders through a single, non-invasive test." At 18.5 weeks gestation, the researchers were able to map the whole genome of a fetus and then reconstructed it using DNA from the mother's blood plasma and saliva from the father. Although fetal DNA is found in the mother's blood plasma, it can be challenging to distinguish which genetic signature belongs to the fetus and which belongs to the mother. As a result the team used a new technique in order to identify blocks of haplotypes (genetic variation), that could be traced back to the mother's genome. The researchers were then able to use this information, together with data from the father's saliva sample, to determine which genomes the fetus inherited. The team then conducted a more intensive examination...

Exercise Linked To Change In DNA

A recent study, published in Cell Metabolism, and conducted by researchers at the Karolinska Institute, demonstrates that exercise almost immediately alters DNA in healthy inactive men and women. The researchers explain that although the genetic makeup is not altered, DNA molecules change structurally and chemically when a person exercises. An example of this is the DNA gaining more or losing parts of methyl groups that are found on sequences of DNA families. Juleen Zierath, Professor of Clinical Integratice Physiology at the Department of Molecular Medicine and Surgery says: "Our muscles are really plastic. We often say 'You are what you eat.' Well, muscle adapts to what you do. If you don't use it, you lost it and this is one of the mechanisms that allow that to happen." During the study, DNA within skeletal muscle was taken from people who had just experienced a round of exercise. The DNA showed less methyl groups than it had before the person's work out. The changes were found in the areas of DNA which work as stopping places for a certain kind of enzymes, called transcription factors. These enzymes are very important in terms of muscles and exercise. Zierath continues: "Exercise is already known to induce changes in muscle, including increased metabolism of sugar and fat. Our discovery is that the methylation change comes first." The authors explain that transcription factors basically open our genes. When methyl groups are secure, the transcription factors are not able to enter through DNA. However, when the methyl groups are not in place, the transcription factors can move about freely and therefore the muscle is able to...

Monkeys Born From Stem Cells

The birth of three monkeys from a stem cellresearch program is being hailed as a major breakthrough in genetic engineering. It appears that the mouse stem cells widely used in studies, follow a different developmental process, that was previously thought to be identical to primate and human. Scientists have opened a window to a new strategy, and one which has seemed out of reach for more than ten years. Now it is possible for cloning primate and even human stem cells, into living breathing organisms. The monkeys were all male and appear to be healthy. The work, by developmental biologist Masahito Tachibana of the Oregon National Primate Research Center, was reported in the journal 'Cell'. Instead of using embryonic stem cells cultured from lines of cells grown in petri dishes, the researchers used early-stage stem cells taken directly from monkey four-cell embryos to create 10 chimeric, or genetically mixed, embryos. The cells were combined from the early stage embryos, so the DNA was mixed, and the fetuses were incubated in female monkeys. Three out of the four survived full term and are currently between four and six months old. They carry mixed DNA from six different genetic lineages. Genetically, it's as if they had as many as six parents, an impossibility naturally. More interestingly, although they have both male and female DNA, they are all developing as males, because masculine genes have dominated the monkeys development. The three rhesus monkeys, named Chimero, Roku and Hex, are said to be normal and healthy. The researchers were able to make monkey chimeras only when they mixed cells from very early stage embryos,...
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