杭州娱乐论坛

first_imgThe Feb. 17 issue of Current Biology1 has a Q&A magazine feature on the genetic code.  After dismissing some myths about it being universal, consisting of only 20 amino acids and obligated to only three codons (there are some minor exceptions to these mostly-true principles: see 04/30/2003), the authors tackle the big question: where did it come from?I heard about a ‘frozen accident’�One of the first proposals, in 1968, for the origin of the code, was Francis Crick’s ‘frozen accident’ model.  But the discovery of alternative codes showed that the code is not frozen.  And similar codons are assigned to similar amino acids, indicating that the code is not an accident.So, how did the code evolve?There are several theories that try to explain the origin of the code.  Most can be classified in one of three major groups.Chemical: posits that direct chemical interactions between amino acids and their cognate codons/anticodons influenced codon assignment.  Studies of binding of RNA aptamers to amino acids showed that, for at least some amino acids – arginine, tyrosine and isoleucine – such chemical interactions do exist.  These theories fail to explain the assignment of codons that do not show direct interactions to their cognate amino acids.Historical: proposes that an initially smaller code grew by incorporation of new amino acids. For example, new amino acids may have captured codons from their metabolic precursors, contributing to the assignment of similar amino acids to similar codons.Selection: suggests that the code was selected to minimize the phenotypic effects of point mutations.  The code’s organization supports this: nonsynonymous substitutions often lead to replacement of an amino acid by one chemically similar, causing little disruption in the protein.Accumulating evidence for these models suggests that they are not mutually exclusive.  Rather, the code probably evolved by an interplay among some or all of them.  Direct interactions of short RNA molecules and amino acids may have fixed the assignment of certain codons, while subsequent assignments may have been driven by history and selection.(Emphasis in original.)1Andre R.O. Cavalcanti and Laura F. Landweber, “Magazine: Genetic Code,” Current Biology Vol 14, R147, 17 February 2004.They just violated Occam’s razor.  They also violated the rule that three wrongs don’t make a right. The “Chemical” theory is the old biological predestination idea that Dean Kenyon abandoned.  If RNA happens to bind to three amino acids better than the 17 others, that does not explain how they subsequently linked via peptide bonds to form a polypeptide with any catalytic activity.  Amino acids do not have the ability to link up by themselves.  Getting just one element of the complex protein machinery that can translate DNA and construct a protein is astronomically improbable, to put it mildly (see our online book).The “Historical” theory is hysterical, because it personifies amino acids.  One cannot ascribe purposeful processes to chemicals.  No cheating with natural selection, either; it cannot even begin to a player unless an accurate system of self-replication is already working.The “Selection” Theory also personifies the chemicals: the code was selected to minimize … point mutations”  Enough of this passive-voice nonsense.  Who selected it, and why would he/she/it want to, if not to optimize the system?  The sentence makes perfect sense in intelligent design theory, but is bizarre otherwise.  No cheating with natural selection here, either.    The authors committed one more foul: card stacking.  All their theories assume naturalistic evolution.  They left out the only theory that explains the observations without violating Occam’s razor: intelligent design. (Visited 41 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img read more

first_imgShare Facebook Twitter Google + LinkedIn Pinterest The 2016 Ohio Beef Expo kicked off on Friday. It’s certainly one of the most popular events for Ohio cattlemen to attend. This event attracts over 30,000 participants from 25 states and Canada each year. The Expo included breed sales, shows and displays, educational events, a highly competitive junior show and a trade show with over 140 exhibitors.On Friday, Ohio Ag Net’s Dale Minyo spoke with Bruce Smith of COBA Select Sires. Listen to the interview here:Bruce Smith Select Sires Beef interview with Dale Minyo 3-18-16This annual event, coordinated by the Ohio Cattlemen’s Association, included breed sales, shows and displays, trade show and a highly competitive junior show. This year’s junior show was the largest ever with more than 850 junior heifers and steers and more than 450 exhibitors competing in showmanship.In the Junior Show, the Grand Champion market animal was the champion crossbred exhibited by Kendra Gabriel from Pickaway County. The Reserve Champion market animal was the reserve crossbred exhibited by Caden Jones of Allen County.The Grand Champion Heifer was the Champion % Simmental Heifer exhibited by Tyson Woodard of Darke County. The Reserve Champion Heifer was the Champion Purebred Simmental Heifer exhibited by Ali Muir of Auglaize County.There were also several breed sales. The Angus sale grossed $183,870 with bulls averaging $3,512 and females averaging $3,473. The Hereford Sale grossed $115,305 with bulls selling for an average of $3,013 and females selling for an average of $2,573. The Maine-Anjou sale grossed $250,050 with bulls averaging $4,270 and females averaging $3,087. The Shorthorn sale grossed $165,260 with bulls averaging $2,369 and the females averaged $3,294. The Simmental Sale grossed $307,520 with bulls averaging $3,753 and females averaging $3,332.On Friday, March 20 at 10:00 a.m. New Holland Agriculture presented a Forage Seminar,l featuring discussions by Dr. Francis Fluharty, Research Professor in the OSU Department of Animal Sciences, and Robert Hendrix, New Holland hay and forage product specialist. Also new in 2016, United Producers, Inc. sponsored an online feeder cattle sale.Over 140 exhibitors are on display at this year’s trade show.Each day was filled with many activities for a wide variety of interests. Sires of several different breeds were on display at the Genetic Pathway throughout the event. Breed shows and parades were held for Angus, Hereford, Miniature Hereford, Murray Grey, and Shorthorns. Other Friday highlights included a Nutrition Seminar and the Junior Show Welcome Party and Fitting Demonstration.The Saturday schedule was full of activity. Breed sales held included Angus, Hereford, Maine-Anjou, Shorthorn, and Simmental. Junior activities included a judging contest, a Beef Quality Assurance Program, and the Junior Show Showmanship Contest. The Trade Show and Genetic Pathway were open as well. Sunday is the final day of the event. The highlight of the day was the Junior Heifer and Steer Show.For more results from the Ohio Beef Expo, go to: http://www.ohiobeefexpo.com/ Feeder Cattle Sale Shorthorn Show Shorthorn Show Hereford Show Over 140 exhibitors are on display at this year’s trade show. Dale Minyo speaking with Bruce Smith at the Ohio Ag Net booth. Ashley Peter, Defiance Co., sets up her Shorthorn heifer for the judge. Karly Goetz, Ottawa Co., leads her ShorthornPlus steer. Nathan Siebold, Madison Co., looks over his ShorthornPlus steer. Blake Martin, Huron Co., with his High% Maine. Maddox Cupp, Fairfield Co., won his Hereford heifer class. Brooke Weeks, Champaign Co., leads her Maine-Anjou steer. Amanda Nething, Richland Co., and her Hereford steer Ryan Flax, Clark Co., and his Hereford steer Josh Elder gives a fitting demonstration for Stock Show University. Kendra Gabriel, Pickaway Co., won her market heifer class. Delaney Jones, Allen Co., with her Simmental steer Samantha Parks, Warren Co., with her MaineTainer heifer Taylor Elliot, Richland Co., watches the judge with her MaineTainer heifer.last_img read more