tag:blogger.com,1999:blog-8508998463866407663.post3843008312467717860..comments2024-01-06T23:47:42.393-08:00Comments on Theobrominated: Plants of the rugby world cup 3.—the rosePhil Garnock-Joneshttp://www.blogger.com/profile/05010415287478039865noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-8508998463866407663.post-7783881360213457062011-09-28T13:38:03.033-07:002011-09-28T13:38:03.033-07:00Here's a link to Jerry Coyne's website, wh...Here's a link to Jerry Coyne's website, where he describes an animal equivalent. <br />http://whyevolutionistrue.wordpress.com/2011/09/28/a-twelve-year-old-cat-with-two-faces/ <br />"Sonic hedgehog" is an animal homeotic gene (yes, sometimes genes are named in even sillier ways than naming them after what happens when they don't work).Phil Garnock-Joneshttps://www.blogger.com/profile/05010415287478039865noreply@blogger.comtag:blogger.com,1999:blog-8508998463866407663.post-66103065014303346122011-09-23T07:49:30.314-07:002011-09-23T07:49:30.314-07:00Homeotic genes control how bodies develop; they...Homeotic genes control how bodies develop; they're really important in our own bodies, determining where different organs are produced. The same genes control similar development in insects and mammals, which is part of the raft of evidence that living things are related through common descent. For instance, there's a fruit-fly gene called EYELESS that turns on the development of eyes (some genes are confusingly named according to what happens when they fail to work). If you take an eyeless fruit-fly embryo and replace its defective EYELESS gene with a functioning eyeless gene from a mouse, it'll develop eyes again: not mouse eyes, but proper fruit-fly compound eyes. That shows the gene instructs other genes to build an eye, but it doesn't control how the eye is built. Our bodies are segmented too (think ribs, vertebrae) and the homeotic genes control how each segment differentiates.<br />In plants it's a bit different, and flowers develop according to three classes of homeotic genes. Class A genes control the outer two whorls of floral leaves (sepals & petals), class B the 2nd and 3rd whorls (petals and stamens), and class C the innermost two whorls (stamens and carpels). It's the AB combination that determines petals, and the BC combination determines stamens. If class C is missing, the developing 3rd whorl is determined by the AB combination to develop as extra petals instead of stamens (which require BC); often the innermost whorl develops as sepals (A) instead of carpels (C), but I'm not sure what happens in roses. There's also an overall master-switch called LEAFY, which turns a developing branch into a flower (when it doesn't work, a stunted leafy shoot replaces the flower).<br />See http://en.wikipedia.org/wiki/ABC_model_of_flower_developmentPhil Garnock-Joneshttps://www.blogger.com/profile/05010415287478039865noreply@blogger.comtag:blogger.com,1999:blog-8508998463866407663.post-69074743611222166712011-09-23T04:19:13.107-07:002011-09-23T04:19:13.107-07:00Fascinating about the double flowers! I never unde...Fascinating about the double flowers! I never understood that properly before. So how does that work - the conversion of stamens into petals?Johanna Knoxhttps://www.blogger.com/profile/09268918125129111587noreply@blogger.com