Tulips are the best flower according to Jane and Michael on Beer with Chocolate. Jane and Michael may have been slightly influenced by their Birthday Adventure in Holland. 
), tulips are not the best flowering plant. Dandelions (from the French dent de lion - lion's teeth) are the best plant. 
In an earlier posting I described a problem that we often use to encourage critical thinking in our undergraduates. The problem is how can E. coli divide faster that the time it takes to replicate it's chromosome? [DNA Replication in E. coli: The Problem]The bacterium Escherichia coli has a single chromosome that is replicated from a single origin (oriC), bidirectionally to the terminus, once per division cycle (Kornberg and Baker, 1992). The cell cycle of slowly growing bacteria is quite similar to that of eukaryotic cells (Boye et al, 1996), with the G1, S and G2/M phases of bacteria termed B, C and D, respectively. E. coli (and certain other bacteria) is capable of very rapid growth in rich medium, with doubling times as short as 20 min. The replication time, however, remains long, with approximately 60–90 min required to replicate and segregate the chromosome. Therefore, the cell cycle is more complicated during rapid growth (Figure 1). If the time it takes to synthesize and segregate the daughter chromosomes (C+D) exceeds one generation time, a new round of replication must be initiated before the previous round is completed (Cooper and Helmstetter, 1968). Thus, initiation occurs at two origins in the 'mother' cell. It can even occur in the 'grandmother' cell at four origins if the time it takes to replicate and segregate the chromosome exceeds two generations. These initiations at two or four origins occur simultaneously, as one event per division cycle (Skarstad et al, 1986). While E. coli and Bacillus subtilis are two examples of bacteria capable of performing multifork replication, other bacteria, such as Caulobacter crescentus, are not. Eukaryotic cells do not replicate with overlapping cycles, but do initiate DNA replication at multiple replication origins, and thus perform a different kind of multifork replication, with the multiple forks on the same copy of the genome (Diffley, 2004).
Figure 1:Replication pattern of rapidly growing E. coli wild-type cells. Cells (yellow) with chromosomes (blue lines) and origins (black squares) are drawn schematically to show the number of replication forks and origins at different stages of the cell cycle. In this example, initiation of replication occurs at four origins at the same time as cell division (bottom). A young cell therefore contains four origins and six replication forks (upper left). As replication proceeds, the oldest pair of forks reach the terminus and the two sister chromosomes segregate. The cell then contains four origins and four replication forks (upper right). Initiation then occurs again at 4 origins and generates 8 new forks giving a total of 12 forks, as cell division approaches (bottom). Because there will be cell-to-cell variability, some cells will contain eight origins before they divide, whereas cells that divide before initiation of replication will contain only two origins (not shown). However, the majority of the cells in the culture will contain four origins.
Fossum, S., Crooke, E. and Skarstad, K. (2007) Organization of sister origins and replisomes during multifork DNA replication in Escherichia coli. EMBO J 26:4514–4522 [doi:10.1038/sj.emboj.7601871]
The 31st edition of Gene Genie has been posted at Adaptive Complexity [Capitalists, Genetic Tests and Your DNA]. Everyone knows there is a lot of crazy stuff on the internet, but did you know there is a lot of great writing about genes, genetics, and human diseases? And believe it or not, sometimes these pieces are written by people who know what they're talking about. If you're looking for what's new in human genetics, you've come to the right place.The beautiful logo was created by Ricardo at My Biotech Life.
Welcome to the 31st Gene Genie, a blog carnival dedicated to great blogging about human genes and how they impact our health. This Mother's Day edition includes an in-depth highlight of the growing industry of personalized genetics.
The data is now in. Russel Doolittle has been working on the evolution of the clotting cascade and the latest results incorporate the information from the lamprey genome. Suffice to say, Behe's claims have been decisively refuted.
If you're not going to follow the Blogger's Code of Conduct, this is what you're supposed to put on your blog. This is an open, uncensored forum. We are not responsible for the comments of any poster, and when discussions get heated, crude language, insults and other "off color" comments may be encountered. Participate in this site at your own risk.Don't say you haven't been warned.
ATHEISTS and agnostics are decent people whose tormented souls will burn for all eternity in the scorching fires of hell, Britain's biggest catholic said last night.Gee, I wonder how he feels about Jews and Muslims?
Cardinal Cormac Murphy O'Connor said non-believers should be respected, right up to the point of death when they will finally come face to face with Satan and his blood-soaked pitchfork.
He told a conference in London: "Those without faith should not be shunned or abused. Jesus and Beelzebub are already cooking something up for them, don't you worry about that."
[Hat Tip: RichardDawkins.net]
Premier Dalton McGuinty started the debate in February when he called for a study of the current practice [Lord's Prayer review ordered].Queen's Park Bureau ChiefThis sounds pretty enlightened. Later on we learned that McGuinty had in mind multiple prayers and not just abolishing the practice altogether.
In a bid to separate church and state – or, in this case, province – Premier Dalton McGuinty wants to end the practice of reciting the Lord's Prayer in the Ontario Legislature.
McGuinty surprised observers at Queen's Park this morning by appealing for an all-party committee to replace the prayer.
"I believe it is time for Ontario's Legislature to better reflect Ontario's reality and celebrate our diversity," the premier wrote to the leaders of the Progressive Conservatives and New Democrats.
"It is time to move beyond the daily recitation of the Lord's Prayer in the Ontario Legislature to a more inclusive approach that reflects 21st century Ontario," he said, noting the prayer was last updated in 1969.
"Our counterparts in other provinces and the federal government have adjusted their customs to reflect the diversity of the population.
"The members of the Ontario Legislature reflect the diversity of Ontario – be it Christian, Jewish, Hindu, Muslim, Sikh or agnostic. It is time for our practices to do the same. That is the Ontario way," McGuinty wrote.
Christians across the province see the Premier's move as a sop to those who think saying the prayer is inconsistent with multiculturalism. Those who disapprove of such a move include Premier McGuinty's own mother. But that has not caused the Premier to waver in his position for change. He is on record saying: "We've got a responsibility to ensure that all people feel truly at home here."Hmmm ... let's see if I understand this correctly. Forcing atheists to recite, or listen to, the Christian prayer every day, is a symbol of "tolerance."
But the move has left many Christians in Ontario wondering if the province is still their home; if it is a place that is in tune with the Christian principles that have informed the province's political and economic values — values that underpin Ontario's success story as a democratic, prosperous province. The Lord's Prayer, recited by Catholics and Protestants alike, is more than words that pay homage to God.
It represents a piece of common ground that Catholics and Protestants could agree on -- a daily ritual that helped in whatever small way to break down the intolerance that existed between the majority Protestants and minority Catholics who founded the province.
In its own small but important way, the recital of the Lord's Prayer is a symbol of the tolerance that has made Ontario the great place it is today to live. That Premier McGuinty would consider dropping the prayer in the name of tolerance is, thus, ironic. It would do a disservice to the province's history and its Christian heritage.
Ontario should keep the Lord's Prayer, add other prayers from different faiths if thought appropriate, and avoid the folly of dismissing history for feel good, fuzzy visions of multiculturalism.
Amino acids come in two different "flavors" depending on the orientation of atoms bound to the central α-carbon. The two possibilities are L- and D- configurations. In the examples shown here, you can see that the two forms of serine, L-serine and D-serine, are mirror images of each other. These forms are called stereoisomers because they contain the same atoms with different mirror image arrangements.
When amino acids are synthesized in a chemistry laboratory, you often end up with a mixture of equal amounts of L- and D- stereoisomers. When you examine the amino acids found in meteorites and in the vicinity of stars, you find a mixture of both stereoisomers. These are called racemic mixtures since the process of converting one stereoisomer into another is called racemization.
In modern cells, this reaction is catalyzed by sophisticated transaminases but in the beginning it would have been catalyzed by short peptides that formed spontaneously in the primordial soup. Such reactions are stereospecific, the modern reaction only produces L-alanine and never D-alanine (well, hardly ever!). Let's assume that a similar reaction in the beginning produced, by chance, L-alanine.
1. This is a modified version of an article that was originally posted on talk.origins in January, 2004.
I've started reading microcosm by my favorite science writer, Carl Zimmer [Buy This Book!]. Watch for a review, coming soon.E. coli faces a far bigger challenge to its order when it reproduces. To reproduce, it must create a copy of its DNA, pull those chromosomes to either end of its interior, and slice itself in half. Yet E. coli can do all of that with almost perfect accuracy in as little as twenty minutes.Today, we're not concerned about the 20 minute generation time but I note, for the record, that the average generation time of E. coli, in vivo, is about one day. I also want to mention that the 20 minute generation time is an extreme example that's achieved only under the most extraordinary circumstances. Typical generation times in the lab are about 30 minutes.
The first step in building a new E. coli—copying more than a million base pairs of DNA—begins when two dozen different kinds of enzymes swoop down on a single spot along E. coli's chromosome. Some of them pull the two strands of DNA apart while others grip the strands to prevent them from twisting away or collapsing back on each other. Two squadrons of enzymes begin marching down each strand, grabbing loose molecules to build it a partner. The squadrons can add a thousand new bases to a strand every second.What Carl is referring to the the assembly of replication complexes (replisomes) at the origin of replication. Once those complexes are assembled, replication fires off and proceeds in opposite directions (bidirectionally) until the two fork meet at the opposite side of the chromosome.
Uncommon Descent is the Intelligent Design blog of Bill Dembski, Denyse O'Leary and their friends. It represent the best that the IDiots have to offer.Ben Stein has a dangerous idea. His idea is that professors and teachers who express skepticism about Darwinism are likely to find themselves not granted tenure, castigated and ridiculed, and disqualified from the opportunity to have research papers published.No, your eyes are not deceiving you. Re-read that last paragraph. For all we know Stein may be a secret evolutionist. He's only interested in academic freedom. It's just a coincidence that the phrase "No Intelligence Allowed" uses the same word as Intelligent Design.
. . .
Having reviewed the movie myself, it appeared that Stein was trying to make the case for academic freedom, not attempted to convert anyone to a particular ideological position.
Stein, in fact, never makes it known what particular beliefs he holds personally, he merely makes it known that he is disgusted by the idea that someone could lose their job over honest doubts about Darwinism.
A big event just happened at Evolutionblog—Jason Rosenhouse got tenure [Tenure!]. Congratulations Jason. I got tenure! Yay! By my count it's been about fifteen years getting to this point. I started studying mathematics seriously in my last two years of college (a rather late start in this profession). Then it was five years of graduate school, three years as a post-doc in Kansas, and now five years at JMU. Pretty satisfying. Suddenly that obnoxious and contentless rejection letter I received a month ago on a paper the journal should have been honored to publish doesn't seem to sting so much. (I'll just patch it up and send it off to the next journal, where it will languish for ten months to a year. What do I care? It's not like I'm in any great hurry to publish anymore!)I guess this is when we discover that Jason is really a closet IDiot.
So there you go. Guess now I can tell you what I really think...
"for their discoveries concerning signal transduction in the nervous system"
Arvid Carlsson (1923 - ) and Paul Greengard (1953 - ) received the Nobel Prize in Physiology or Medicine for their work on identifying dopamine as a neurotransmitter. They also showed that L-dopa [Monday's Molecule #70], a precursor of dopamine, could relieve the symptoms of dopamine depletion and help control the symptoms of Parkinson's disease. They shared the prize that year with Eric R. Kandel. Your Majesties, Your Royal Highnesses, Ladies and Gentlemen,
This year's Nobel Prize in Physiology or Medicine concerns the most complex structure in the universe that we know of - the human brain. It consists of 100 billion nerve cells, which is the same number of cells as the total number of human beings that have ever lived on this earth.
We talk about the "Internet revolution"; 35 million Internet users who communicate now and then - what is that compared to the nerve cells we all carry within ourselves! 100 billion nerve cells that communicate continuously.
It is this communication, "signal transduction in the nervous system," which is the subject of this year's Nobel Prize. A single nerve cell forms thousands of contact points, so-called synapses, with other nerve cells. In these synapses the nerve cells communicate by chemistry; one cell releases a transmitter, which reaches the other cell.Professor Arvid Carlsson proved that dopamine is such a transmitter. The general belief was that dopamine was a precursor of other transmitters and of little functional importance. However, Professor Carlsson was able to show that dopamine existed in specific parts of the brain and concluded that it was a transmitter in its own right.
He then used a naturally occurring substance, reserpine, which empties the dopamine from the nerves, and found that the animals lost their ability to move. He realized that it must be possible to restore the dopamine levels with L-DOPA, a precursor of dopamine. In a conclusive, dramatic experiment he showed that the animals regained their ability to move when he gave them L-DOPA.
Reserpine had depleted dopamine and had given the animals the symptoms of Parkinson's disease, that is, rigidity and inability to move and react to stimuli in the environment. When the animals were given L-DOPA, dopamine was produced again in their brains. In this way the idea of treating Parkinson patients with L-DOPA was born. This enables millions of patients around the world to live a normal life.Professor Paul Greengard showed what happens when dopamine and other similar transmitters stimulate a nerve cell. Receptors on the cell surface activate enzymes in the cell wall, which starts the production of second messengers. These messengers travel into the cell and activate a protein kinase, which starts to bind phosphate groups to other proteins, in this way altering their function. This leads, for example, to the opening of ion channels in the cell membrane and a change in the electrical activity of the cell.
Professor Greengard then showed that dopamine and other transmitters affect a central regulatory protein, which has been called DARPP-32. Like the conductor of an orchestra, it tells other proteins when and how to be activated.
This so-called "slow synaptic transmission" controls our movements and also those processes in the brain that elicit emotions or react to addictive drugs such as cocaine, amphetamine and heroin.
Professor Eric Kandel showed that transmitters of the same type as studied by Arvid Carlsson, via the protein kinases characterized by Paul Greengard, are involved in the most advanced functions of the nervous system such as the ability to form memories.
Imagine how difficult or impossible it must be to study how memory is formed in a human brain with 100 billion nerve cells. Eric Kandel, therefore, did something which is classical in all natural science: He chose to study a simpler model system, a sea slug, Aplysia, which has 20,000 nerve cells. He did it with the conviction that even primitive animals must learn in order to survive.
The sea slug has a withdrawal reflex protecting its gills. If they are touched repeatedly, they react less and less - just as human beings do when subjected to an unexpected touch. If, on the other hand, the touch is forceful the reflex is amplified and becomes stronger and stronger.
The habituation or amplification effect lasts only for a few minutes. One may say that the sea slug exhibits a short-term memory. If the forceful stimulus is repeated several times, the sensitization may remain for weeks, that is, the sea slug develops a long-term memory.
Professor Kandel was able to show that habituation to touching was due to changes in the synapse, the contact point between the nerve cells. During habituation less and less transmitter was released.
The forceful stimulus that formed the long-term memory worked in a completely different way. Second messengers activated protein kinases that entered the cell nucleus and started the production of new proteins. This, in turn, brought about a change in the form and function of the synapse. What we call memory is, thus, elicited by direct changes in the billion of synapses that form the contact points between the nerve cells.
I am convinced that you and I will remember this Nobel ceremony for many years. This is because of the dopamine which Arvid Carlsson discovered, enabling the brain to react to what we see and hear; the second messengers that Paul Greengard described, carrying the signals into the nerve cell; and the memory functions that Eric Kandel found to be due to changes in the very form and function of the synapses.
Dear Arvid Carlsson, Paul Greengard and Eric Kandel. Your discoveries concerning "signal transduction in the nervous system" have truly changed our understanding of brain function. From Arvid Carlsson's research we now know that Parkinson's disease is due to failure in synaptic release of dopamine. We know that we can substitute the lost function by a simple molecule, L-DOPA, which replenishes the emptied stores of dopamine and in this way, give millions of humans a better life.
We know from Paul Greengard's work how this is brought about. How second messengers activate protein kinases leading to changes in cellular reactions. We begin to see how phosphorylation plays a central part in the very orchestration of the different transmitter inputs to the nerve cells.
Finally, Eric Kandel's work has shown us how these transmitters, through second transmitters and protein phosphorylation, create short- and long-term memory, forming the very basis for our ability to exist and interact meaningfully in our world.
On behalf of the Nobel Assembly at Karolinska Institutet, I wish to convey our warmest congratulations and I ask you to step forward to receive the Nobel Prize from the hands of His Majesty the King.
[Photo Credits: The photo of Arvid Carlsson celebrating is from "The Nobel Prize did change my life!" . The photo of Paul Greengard with his wife Ursala von Rydingsvard is from The New York Times. Greengard used his prize money to fund an annual $50,000 award to an outstanding female medical researcher.
