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Researchers recently put that assumption to the test across three generations of mice, tracking the chemical tags that switch genes on or off. <\/p>\n
The results didn\u2019t add up the way the textbook says they should.<\/p>\n
Beyond Mendel\u2019s pea plants<\/p>\n
The team behind the work wanted to know how often the standard rules of inheritance actually hold up. <\/p>\n
They focused on something Mendel could not see in his pea plants: DNA methylation<\/a>.<\/p>\n The tags work as a chemical switch system, attaching to DNA and turning specific genes on or off without changing the genetic code itself. <\/p>\n They sit on either copy of a gene, and they pass from parent to child.<\/p>\n Dr. Andrew Feinberg, Bloomberg Distinguished Professor at the Johns Hopkins University School of Medicine<\/a>, co-led the research with colleagues at Texas A&M University<\/a>.<\/p>\n Tracking inheritance in real time<\/p>\n To follow how the tags travel, the researchers bred three generations of laboratory mice \u2013 26 in the founding group, 34 in the next, and 19 in the third.<\/p>\n The experts sampled liver and muscle tissue from each animal and read both the genetic sequence and the methylation pattern on the same DNA molecules.<\/p>\n Long-read sequencing made the dual read possible. <\/p>\n It captures far longer stretches of DNA than older methods could, letting the team see methylation tags sitting far from the genes they regulate.<\/p>\n Most of what the team saw lined up with Mendel. About 93% of the methylation patterns followed his classic rules in some form. The remaining 7% did not.<\/p>\n That came out to roughly 522 sites where the tags broke from the script. <\/p>\n In addition, 54 of those sites showed something stranger: methylation tags in offspring that were nowhere to be found in either parent.<\/p>\n A pairing between two mice with no methylation on a particular spot in the genome should produce offspring with no methylation on that spot. <\/p>\n The team kept finding offspring with methylation on both copies.<\/p>\n Evidence of natural paramutation<\/p>\n The strangest result involved a phenomenon called paramutation<\/a>. The methylation on one copy of a gene somehow gets copied onto the other copy. <\/p>\n Both copies are tagged, even when only one parent contributed the tag.<\/p>\n Researchers had documented this in plants, flies, and genetically engineered mice \u2013 but never in mice with no genetic tampering. <\/p>\n A possible link to fertility<\/p>\n The paramutation showed up in a gene that helps drive normal sperm development in mice and humans. <\/p>\n Earlier work<\/a> has tied reduced function of the human version to infertility.<\/p>\n That puts the new finding in fertility-research territory \u2013 not as a definitive link, but as a pattern worth tracking.<\/p>\n Genomic imprinting<\/a> is one well-known way that inheritance breaks from Mendel\u2019s rules. A tag from the mother silences her copy of a gene, or one from the father silences his.<\/p>\n The silencing depends on which parent contributed the copy, not on which version of a gene is stronger or weaker. <\/p>\n Feinberg\u2019s team identified five additional genes that behave this way, expanding what had been a thin catalog in the mouse genome.<\/p>\n Environmental pressure and epigenetics<\/p>\n Methylation tags can come from outside the genome. Diet, stress, and environmental exposure have all been linked to changes in methylation patterns in earlier research<\/a>.<\/p>\n Some of those changes can pass down to offspring. That makes the new findings unusual. <\/p>\n Epigenetic inheritance<\/a> that changes in response to the environment could spread through a population faster than waiting for a random change in the DNA sequence itself.<\/p>\n \u201cNon-Mendelian patterns of inheriting epigenetics could be a faster way to acquire diverse or new traits than alterations in the genomic sequence itself, especially in response to environmental pressures,\u201d said Feinberg.<\/p>\n Expanding the rules of inheritance<\/p>\n Until this study, paramutation in mammals had been a laboratory curiosity. It was produced only through direct genetic engineering. <\/p>\n These mice showed it happening on its own, in a genome no one had altered.<\/p>\n Feinberg and his colleagues now plan to apply the same approach to human genomic data.<\/p>\n The team will look for similar patterns in families to confirm whether this kind of inheritance occurs in people the same way it was just found in mice.<\/p>\n Clinical geneticists tracking inherited disease may want to read both the DNA sequence and the methylation pattern together when standard genetic explanations fall short.<\/p>\n If a condition runs through a family without an obvious genetic cause, the answer may sit in a layer that standard sequencing tools never read.<\/p>\n The study is published in the journal Nature Genetics<\/a>.<\/p>\n Image Credit: Art design by Michael Koldobskiy and Andrew Feinberg, illustration by Kate Zvorykina<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"When two mice both carry an unmarked copy of a gene, their offspring should carry an unmarked copy…\n","protected":false},"author":2,"featured_media":692307,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[64,63,128],"class_list":["post-692306","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-au","tag-australia","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/692306","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=692306"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/692306\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/692307"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=692306"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=692306"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=692306"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}