X inactivation is a type of gene dosage compensation. In humans, the sex chromosomes X and Y determine the sex of an individual - females have two X chromosomes (XX), males have one X and one Y chromosome (XY). All of the genes on the Y chromosome are required in male development, while the genes on the X chromosome are needed for both male and female development. Because females receive two X chromosomes, they inherit two copies of many of the genes that are needed for normal function. Extra copies of genes or chromosomes can affect normal development. An example is Down's syndrome, which is caused by an extra copy of part or all of chromosome 21. In female mammals, a process called X inactivation has evolved to compensate for the extra X chromosome. In X inactivation, each cell 'switches off' one of its X chromosomes, chosen at random, to ensure the correct number of genes are expressed, and to prevent abnormal development.
Here is a helpful eleven minute description of what it is and why it's important by Etsuko Uno and metafilter's own Drew Berry in a fucking gorgeous Goodsell-esque 3D animation.[more inside]
Epigenetics (prev) is the study of changes in gene expression or cellular phenotype, caused by mechanisms other than changes in the underlying DNA sequence. David Epstein, a senior writer for Sports Illustrated has written about this topic for his book The Sports Gene (not as reductive as the title might suggest), but cut the chapter because the material he researched was so new as to require that he "caveat the writing rather heavily." Instead, he shared his chapter How an 1836 Famine Altered the Genes of Children Born Decades Later on IO9. You can read or hear more about the book in a half-hour segment from NPR's Fresh Air, opening with a story of Jennie Finch, a softball pitcher who "just whiff[ed] the best hitters in the world." (Related video clip: FSN Sport Science - Episode 7: Myths - Jennie Finch, on the force of fast baseball vs softball; ends with smarmy teaser for a "sex test")
Study Finds Epigenetics, Not Genetics, Underlies Homosexuality: Epigenetics – how gene expression is regulated by temporary switches, called epi-marks – appears to be a critical and overlooked factor contributing to the long-standing puzzle of why homosexuality occurs. In the current study, researchers from the Working Group on Intragenomic Conflict at the National Institute for Mathematical and Biological Synthesis (NIMBioS) integrated evolutionary theory with recent advances in the molecular regulation of gene expression and androgen-dependent sexual development to produce a biological and mathematical model that delineates the role of epigenetics in homosexuality.
A pilot study testing for statistically significant blood biomarkers found in early-onset MDD: "Discovery of blood transcriptomic markers for depression in animal models and pilot validation in subjects with early-onset major depression" [PDF], published by the online, open source journal Translational Psychiatry**, April 2012, Volume 2. [more inside]
Did you inherit your parents stress? Your grandparents stress? What about their environmental enrichment? Current research in rats is exploring possible mechanisms through which stressful and positive environments could affect our future children and grandchildren. Also something to consider in tandem: many of the genes associated with addiction and mental illness are also associated with resiliency. [more inside]
Epidemiology: Study of a lifetime. "In 1946, scientists started tracking thousands of British children born during one cold March week. On their 65th birthday, the study members find themselves more scientifically valuable than ever before." [more inside]
The winter of 1944–45 is known as the ‘Hunger Winter’ in The Netherlands, which was occupied by the Germans in May 1940. Beginning in September 1944, Allied troops had liberated most of the South of the country, but their advance towards the North came to a stop at the Waal and Rhine rivers and the battle of Arnhem. In support of the Allied war effort, the Dutch government in exile in London called for a national railway strike to hinder German military initiatives. In retaliation, in October 1944, the German authorities blocked all food supplies to the occupied West of the country. Despite the war, nutrition in The Netherlands had generally been adequate up to October 1944. Thereafter, food supplies became increasingly scarce. By November 26, 1944, official rations, which eventually consisted of little more than bread and potatoes, had fallen below 1000 kcal per day, and by April 1945, they were as low as 500 kcal per day. Widespread starvation was seen especially in the cities of the western Netherlands. Food supplies were restored immediately after liberation on May 5, 1945.But for many, who weren't even born when it started, the hongerwinter continues. Why? In part because "certain environmental conditions early in human development can result in persistent changes in epigenetic information" via DNA methylation. Epigenetics seems like a little bit of Lamarckism: environmental effects on a parent -- or even a grandparent -- can be passed to offspring, even without permanent changes to DNA. (previously)
"Epigenetics : the lives of your grandparents – the air they breathed, the food they ate, even the things they saw – can directly affect you, decades later, despite your never experiencing these things yourself. This work is at the forefront of a paradigm shift in scientific thinking, in which the environment can impact our health for generations to come."
Like mutation, but rinses out in four generations! A new study finds that exposure to high levels of environmental toxins produces epigenetic changes in rats' sperm. "Epigenetics does not involve DNA sequence changes but chemical modification of the DNA." Ultimately, this may help to explain why certain human diseases, such as breast and prostate cancer, are becoming more common. The increase in the incidence of these diseases cannot be accounted for by a normal rate of genetic mutation, but epigenetic damage could be the culprit.