source : answersdrive.com
Which way does translation occur?
The mRNA is single-stranded and therefore only contains three possible reading frames, of which only one is translated. The codons of the mRNA reading frame are translated in the 5’→3′ direction into amino acids by a ribosome to produce a polypeptide chain.
So, what direction is RNA synthesized?
The enzyme then progresses along the template strand in the 3′ to 5′ direction, synthesizing a complementary RNA molecule with elongation occurring in the 5′ to 3′ direction. The DNA sequence also dictates where termination of RNA synthesis will occur.
How is RNA synthesized from DNA?
Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA (especially mRNA) by the enzyme RNA polymerase. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language.
Which does not occur during translation? tRNA pairs… – Brainly.com – During the process of translate the genetic code carried by the messenger RNA is decoded by the help of a transfer RNA and is used to make sequence of amino acids and then proteins. This is the process that occurs before translation in the nucleus of a cell.loss is inevitable during translation.but which level of language is more liable for loss (morphological , syntactic or semantic? Semantic losses, I think are more liable than anything else, but do such semantic losses necessarily affect the comprehensibility of the source text?Before this translation process occurs, a gene must have undergone a process called TRANSCRIPTION to yield a single stranded mRNA. However, the transcription of DNA into a complementary strand of mRNA does not occur during TRANSLATION.
At what level of languages losses happen during translation? – Translation means converting the information present in the DNA into proteins. Now, in the process of translation, tRNA, mRNA, and Ribosomes play an essential role. tRNA pairs with complementary mRNA via ribosomes. A protein is formed which is nothing but a string of amino acids.Unlike cap-dependent translation, cap-independent translation does not require a 5' cap to initiate scanning from the 5' end of the mRNA until the start codon. At the end of the initiation step, the mRNA is positioned so that the next codon can be translated during the elongation stage of protein…Object. Do you know the man who talked to me? The peaches that are lying on the table are tasty. We will stay at a hotel which is next to the beach. That is the film which is very exciting.
Which does not occur during translation? tRNA pairs… – Brainly.com – Do Borrowed Words Change or Do They Remain the Same? It is quite natural that political terms frequently occur in the international group of borrowings: politics, policy, revolution, progress, democracy, communism Translation-Loans. The term loan-word is equivalent to borrowing.The cell cycle has three phases that must occur before mitosis, or cell division, happens. These three phases are collectively known as interphase. During G1, a lot of protein synthesis happens in order to increase the amount of cytosol in the cell. Cytosol is the liquid inside the cell, but outside the…Its a Mock Exam question: Which three occur during JSP page translation ( Choose 3). 1.jspinit Method is called 2.JSP page implementation class is created 3.JSP page implementation class is compiled 4.JSP page is validated for syntactic correctness 5.The associated tag files are validated for…
Suicidal Thoughts Made Her PLAN Her OWN FUNERAL!!!⚰️ – [♪ Music ♪] My body is not a temple of sickness and disease! In the mighty name of Jesus Christ! [♪ Music ♪] Sister, we welcome you in the name of Jesus Christ! Tell us your name and where you are from.
My name is Ulrika Edren and I am from Sweden. Tell us, what is your testimony? It all started in 2005. I was working at the airport as a manager, I had an organization and I was responsible for 750 people. I was working from early in the morning until very late in the evening. I had a family of two boys, two sons. and I was not with God at that time. I lived in a relationship but I was not married. I was working very hard and I hardly saw my family. That made me feel very very bad. I wasn't giving my family what they needed, I wasn't eating anything, I wasn't drinking anything, I was not resting at all. This made me start having very very black thoughts and bad thoughts about myself. I ended up being burned out. I fell into a very very deep depression. I asked for help, so, I went to a psychiatrist. They told me that I was totally burned out. Almost reached a point of not existing. I was spending almost all of the time in my bed crying. Finally, my children were taken away from me. Why did they take your children from you? They took my children away because I couldn't take care of them, because I couldn't take care of myself. I started to get very very bad thoughts inside my head, voices trying to tell me to commit suicide. Because I wasn't eating, they wanted to put me in a hospital. I was just skin and bone! What was happening with your suicidal tendencies? What were you thinking and what did they lead you to do? The thoughts told me to plan my own funeral. They made me to sell and give away everything that I had. I gave away everything! My clothes, my belongings, they made me quit my friendships. I didn't have any contact with my children for several years. I think for about four years. My family left me as well and I was totally isolated. You told us that you had sold your belongings. Was it because you wanted to hurt yourself? Tell us in detail what was happening. Yes, they wanted to make me commit suicide. During the night, I couldn't sleep if I didn't have worship songs on. I would wake up during the night screaming, with strangle marks on my neck, and I would also see and hear demons! When I was worshiping it was fine, but when I stopped everything would come to me again. Could you experience this only in the dream or could you feel it in the physical as well? No, I saw them, I felt them and I had strangle marks on my neck when I would wake up. I tried to get help, of course, but nobody could help me. So, I almost lost my home, as well! I had a big house during that time… Just four days before I lost my home, a friend helped me to get another flat. What was the reason you lost your house? I sold the house because I was planning for my funeral! I shouldn't have any life – it had already been planned by the demons. So, four days before I become totally homeless, alone, I got a place to stay with a friend. You said that you were in your bed daily and you were not feeling well at all, you were depressed. Tell us, what was going on with your job? I couldn't go to my job, of course. I was in my bed. I still had my job, but I was not working. After a while, I came here. How did you learn about the SCOAN here? I heard about it from a friend, he was really thinking that this church is alive! Sister, we can't wait to hear what has happened in your life! A lot of things happened in my life! I got my children back! [Applause] My youngest son stays at my place and my eldest son bought a house next to mine. Also, I have a good contact with my family. I have a business, I rent out houses. But the most important thing is that I have a very close relationship with God. [Applause] We want to know about the depression issue that you used to have. Is there depression in your life now? No! Definitely not! [Applause] Do you still have suicidal tendencies? No! Tell us, how do you feel now? How are your thoughts? I live for God and I want to share what I have been going through with others. Do you sleep in your bed all day now? Do you cry, do you feel sad? What is happening? No! I don't! I feel joy! [Applause] Tell us about your dreams. How are they now? I have ordinary dreams. Do you plan your future? Yes, I do! I want to live the real life, the life that God gave me from the start. Amen! Hallelujah! We are happy! Words are not enough! [Applause] Tell us, what is your advice to all people who may still be trapped in depression? Never give up hope! Live next to God and worship Him! Seek help if you need it. That is very important!
You are not alone. Live in the Word! Amen, we praise God! Tell us, what is your promise to God Almighty for what He has done in your life? I am totally His! [Applause] We praise God! At this point we would like to encourage you to make the Word of God the standard for your life, so that this deliverance you received may remain permanent, in the name of Jesus Christ! Amen! Amen! [♪ Music ♪] .
9FF – Weltrekorde der letzten 20 Jahre – GT9, V400… – Teil 1 – Hello, here we are again.
As announced in the last series, today we have our world record vehicles on the subject. When you start a company you need an idea that you can somehow manage to get known as quickly as possible. It doesn't make much sense when you say: “I build really great cars”, but nobody knows and nobody sees it and nobody notices. And that's why we quickly came up with the idea: We have to distinguish ourselves with something very special and what can be marketed particularly well are simply records. Records have the great advantage that, in principle, every journal, every magazine, everybody who distributes news immediately jumps up and says: “Man, I want to report on it.” That means, you have relatively little organization and little marketing, what you have to do it yourself. You break a record and can actually almost wait for the various journalists and reporters to get in touch and report on it. So the idea was born and then of course it was carried out. We had to think about what we can build to break any record and, above all, which one is best . In this case, the maximum speed was obvious. When we founded in 2001, McLaren's speed record was still 372 and the tuners were all somewhere in the 330, 340, 350 range, so basically where fast production cars are already driving nowadays. The cars had a lot less power overall and weren't as good as they are now. Well, at least we then thought about 350, 370, if we want to build something real, then we have to crack the 372 first and then ideally the 400 at some point. 400 is of course a long way off from 370 You can imagine that the power and resistance of driving increases exponentially. When I'm at 370 and sitting in a McLaren that had great aerodynamics, the F1 and already 660 or something like that horsepower, then of course we need exponentially more to get from 370 to 400. That means it was clear to us that we had to build a strong car and one with great aerodynamics. When we started with the first car in 2003, that was of course a 996 Turbo, at the time it was also the most powerful series Porsche, there was a 996 Turbo 3.6 liter twin-turbo engine, relatively simple with normal turbochargers, All-wheel drive with six-speed gearbox or Tiptronic, which of course is ruled out for such a record-breaking vehicle at high speed. Then we took a very close look at this base vehicle. What can we change to optimize aerodynamics, optimize performance, how much performance do we actually need and above all, where can we test it? Which route is actually suitable to be able to drive well over 370? As luck would have it, we were invited by the magazine, at that time still Auto Bild Sportscars Test & Tuning, to a big event in Nardò in cooperation with Continental as the tire manufacturer, who wanted to present their special Continental V-Max tires, which for Speeds up to 360 was released. A special feature are usually all the Z tires with special approval 300, 320, 330 but the Continental V-Max was allowed to go up to 360. So we were invited and were then under pressure, luckily we had a 996 Turbo, which we then started with have to remodel. Back then it was called T6. We then removed the four-wheel drive, converted it to a two-wheel drive, built a cooling system into the gearbox because we knew we would drive at full throttle for a long time with very high power, and we built in a long sixth gear. All things that we did for the first time back then. Have the translation perfectly matched to our maximum speed of 7000 revolutions that we could reach exactly at 7,000 380. Had to have an extra long sixth gear built and so on, so it was a huge effort. Then changed a lot on the vehicle. Charge air cooling, brakes, undercarriage set very low, a water cooling system built back then in 2003, an injection molding for charge air cooler, at that time still with windshield washer nozzles and I don't even know what kind of pump. We got a high-pressure pump from somewhere, at least things that didn't even exist back then but are now in series production in the 911 GT2 RS. With us, of course, in a simplified version, but we already had it in the car back then, 15 years before Porsche installed it. Well, at least the event came and the car ran very well. It was my first time in Nardó. Nardò is a very large circle, 12 kilometers absolutely round. That means it goes around the curve continuously, easily but at least. The cant is relatively small in Nardò and you have 0.75 g of lateral force at a speed of 350. That means with a g it is actually the end of the working day, which means that no car can manage much more than 1 g in a curve in the long run. So you are very, very strong at the limit, so it was difficult for me to drive there for the first time. But the car, as I said, went very well. In the first attempt 369, in the second attempt 376. We lost the McLaren in one fell swoop and were almost 40 km / h faster than the second fastest, which was also a Porsche tuner who achieved 336. Incidentally, that was the last time the owner or managing director of this Porsche tuning company congratulated me on a record. After that, when the records got even faster, there was unfortunately no congratulations. I think then the congratulations, I would say maybe turned into envy. So the first project worked very well. Our T6 excellent, directly behind the McLaren. It was good, but we were still a long way from the 400. Then the next thing came in 2004, of course we didn't want to give up, the idea, what do we do now? We have to improve the aerodynamics and we need even more power. The T6 had 730 hp, something that was already a record for Porsche at the time, nobody had that much on the road. With 3.6 liters and really minor modifications, only large turbos and great electronics. So we knew we had to do something with the performance and with the aerodynamics. Because the turbo is so wide, we thought about building a GT3 next . A GT3 that we are converting as a biturbo. Because the GT3 is narrow, there is little frontal area, little frontal area means good aerodynamics. So we take such a vehicle. In addition, the GT3 is already equipped with the same engine as the turbo, namely the butcher's engine . Already has two-wheel drive with six-speed gearbox. The car was actually the ideal basis for us to build something really fast out of it. So off we went. What do we do with the engine? 3.6 liters was good with 730 hp. What else is there? We make 3.8 liters. Back then an absolute sensation in 2004, nobody built it. So we have large pistons made, large cylinders made, 3.8 liters built. What's still up Heads are pretty small, so we need big heads. What can we take Long researched and sought: Old GT3 Cup version. Everything is perfect, unfortunately the oil ducts for the VarioCam plus are missing . Of course, we didn't notice until we had built the first engine a long time ago. Everything apart again, channels milled in, everything by hand. Wonderful, the car drove like a one. We had titanium connecting rods made for the car ourselves so that they fit on the turbo crankshaft in combination with our three eighth pistons. We had camshafts built for us, very sharp ones and so on and so on, had KKK in the prototype department build us k27 loaders, just as they used to run in the 962 racing vehicles that had a lot of power. We are then with a special exhaust and catalytic converter and all the trimmings, so let’s say, not that far away from good and bad, then at a speed of 7500 rpm we got 843 hp. So again over 100 hp more than with the T6 version, so were already further ahead in terms of performance. In combination with the more aerodynamic car, which also had an RSR smooth carbon underbody, built a very special rear wing that sat behind the car, similar to an old Porsche Moby Dick long-tail version, a new front section with very small cooling air intakes and so on and so on, narrow rims even with covers on them. So we optimized, optimized, optimized, optimized the car , built in a very strong lock, because we thought: That's awesome. It was almost 100% blocked, so we were invited to Nardò by Auto Motor Sport again, either by luck or by chance , and thought: Cash desk 376 last time, we know how things are going, now we're really driving fast. Think. Our lock really killed us off, because if there is always a steady turn around the corner, but the rear axle is 100% locked, the car will, in principle, drive straight ahead with a lot of power until the tension in the entire drive train is so strong that a wheel spins briefly because when I drive around a bend, the distance of the inner wheel is smaller than that of the outer wheel. That means there is a speed difference somewhere, meaning the car always hit the hook. Every 150 meters he moved terribly because it went crazy once in the back. Well, nonetheless, I drove it in darkness 355. But there really was nothing left, it was absolutely the ass off, especially with me. Afterwards the testers from Auto Motor und Sport said: “Don't get in line, your car has so much smoke, now we'll show you how to do it properly.” At 320, the head tester broke off and said the car was undrivable. I did a good 355, so it wasn't that bad that day. So we knew where the mistake was. Lock out, unlocked differential in, half a year later Nardò rented again as a company, for a whole day on December 12th. my wedding day. My wife went to the cinema at home because she couldn't stand it and was scared and I sat on the track for eight hours and have different versions of rear wings and front spoiler and underbody and higher front, higher rear, lower front, different air filters everything Possible thoroughly tested until the 392 was finally on the clock. 392 was then completely turned off. End of working day. Nardò, nothing more was possible that day. But that was enough for us , because in the meantime McLaren had topped up with 390 or something and we cracked that again. So we were again the fastest street-legal car in the world, although we had n't reached the 400, I was also pretty annoyed myself, although in the video I think about it from Sat1 I do "Yes, clean", but that was actually more the McLaren-record and not the back missed 400. Because the driving experience with the V400 but overall rather, well, I'd best say was modest, the aerodynamics of Elfers is when the viewed from the side in Principle similar to that of an airplane wing. The long, sloping stern creates an incredible amount of lift at the rear. But lift on the rear axle is the enemy of driving dynamics at high speeds, so it was clear to me: With the 911 in its basic form, regardless of what we do with aerodynamics, we will probably not really be able to reach the 400, at least with a sensible driving experience , unless you put in 2000 hp, then of course it always works, then I can also put a huge wing on it, but that wasn't the goal. I wanted to build an efficient car, with an output of maybe around 1000 hp, which still drives 400 and then drives so well that not only a racing driver can do it or someone who is not afraid, but everyone sits down and maybe also 400 drives with one hand. The idea was born. What do we have to do? It doesn't work on the 911 basis, so what could be more obvious: We have to build our own car. Own car, how do you do that? What do I have to adhere to? What are the requirements, what are they with Tüv, what about approval, what about strength and calculation? At the time we started with it, in 2005, shortly after the world record with the V400, we had six employees in the company, I think. So we weren't a corporation, but a very small company. With a very small company you can actually only think relatively small and not make very big leaps, I can't get a company that says: I'll calculate a complete framework here and I'll make you an interpretation and I'll do it do this and that, but it was learning by doing and we did everything ourselves. ———-
Well, how about that going on? In order to somehow pass a crash test and things like that, because they still had to be fulfilled at the time according to the Tüv approval regulations in 2004, we need a front end that is crash-relevant that we can take over from a production car so that we can bypass this crash test. If we were to build, or would have built, a complete tubular space frame, we would have had to drive the car in front of the wall, but if I first build a prototype, which may cost half a million or a million, and then drive it in front of the wall, then I'll be my six -Employees at the company also drove directly in front of the wall, so this option was completely ruled out. And that's why I looked around, where can I find a nice GT3, 996 was back then with a huge rear damage, because I only need the front part. That's exactly how it happened. I found a car, yellow GT3 in Bochum, first owner Atze Schröder, who unfortunately took it backwards somewhere. In the letter, however, there is someone else, the seller says he belonged to Azte Schröder. Well, we took everything out of it, bought a bench, put the thing on the bench and then started sawing the car up completely. I'm referring to one of the first episodes in which I told about my first big project, the BMW 323i, which I sawed up completely because I wanted to build a Schnitzer Rodenstock out of it. It was exactly the same, i.e. sawing the car completely up on the bench, extending the wheelbase 30 cm , i.e. pulling the axle 30 cm further back on the bench, cutting off the roof, installing the engine upside down, converting the gearbox so that you don't have six reverse gears and have a forward gear, put everything together and then start building pipes. Yes, bend a lot of pipes and then gradually a car grew together. It took a long time, we only have the rear area, I believe in sheet metal and GRP and in various other materials and tin, I think three or four times completely new, because we never liked it until the final prototype, which we then afterwards have also tested long and extensively. Yes, it was a very uplifting feeling when we took it for the first test drives after almost three years of construction. I still remember exactly, first test drive on the A44, with the engine running properly for the first time and then turned onto the short connecting freeway in the direction of Arnsberg, so that was it … I don't know when I was so deeply impressed and such a decisive experience in my life had like the first test drive. In all honesty, it was awesome when you say I have a six-person company, I build my own car and drive it on the autobahn afterwards, it was indescribable. Well, after we tested the car relatively well, we had a few tests at Auto Motor und Sport, we even got into a huge snow storm on the way back from Stuttgart , then stopped on the way and said: “Boys, you have to have everything ready at home at the company immediately when I am there. I drove through salt here, the rear area is completely open, we have to clean the car completely immediately, otherwise it will rust away faster, especially the raw aluminum parts in the back of the engine compartment than we can even see. And that's exactly how it was. Auto engine and sport test. The tests were super satisfied and confirmed that the vehicle was handling at least as good as GT3. They did a great pylon test, but didn't have time to drive top speeds and we made up for that shortly afterwards in Papenburg, one of our first tests. We then went to Papenburg, rented Papenburg back then, Mercedes Benz was still owned at the time. At that time it was still relatively easy to do. You could say, dude, during the lunch break, when the test drivers are not on the track between twelve and one, but are sitting in the canteen, you can rent and have the track for a few hundred or € 2,000 – 3,000 then exclusive right. So we got back on the road, the car ran like a charm. 386, 392, after work, rev counter at the end, rev limiter, nothing worked. End of working day. Yeah what did we do? Charged. The sixth gear is wrongly laid out. Continental had made the tires a bit too small, the 275s were a bit smaller, two percent, so the first eight km / h were gone, and the gear was, I think not just 0.82, but 0.84 or or 0 .86 can't remember exactly, at least we were missing a few km / h. All right, so we dismantled the car again, the gearbox out again, the gearbox modified, a new gear made, the thing back in, and off to Papenburg 407. Class. Now we know that we can very quickly. What do we do? We called our friend Ben Arnold, Auto Bild Sportscars, then editor-in-chief and Tuningcheff, and all sorts of things , good friend, and we said: “Ben, we're ready , we want to drive 400 now . Are you there? ”“ Yes, of course. ”So we all agreed to meet again in Dortmund, got into the GT9 in Dortmund, Ben and I drove it to Papenburg, on the move, registered, took to the track , drove 407 409. 409! With GPS and all the zig- zags , we did the whole thing three or four times, got out, congratulated us all, opened the bottle of champagne, then drove to the drive-in of the GT9 to McDonald's, the whole Auto Bild crew did invited plus the notary that we had with us to confirm the world record and then drove back to Dortmund by axis. No trailer, nothing prototype. License plate on, drove there, set a world record, drove back home. No test crew, no special tires, no nothing. Went there on the tire driving on the tire back home. Not 27 people look after a car, change tires seven times, put on a special program so that they can drive the car . Nothing. Ordinary car. Ben Arnold wrote an awesome report , days after that we were in all the magazines in the world. The GT9 was our big breakthrough. We then built various other models of the GT9, with which we did not set any official world records, but gradually increased the output of the car from the original 986 hp, with which we drove the 409, to over 1400 PS and we have a very nice log file of a customer, a Croat who drives such a car, who drove his car on the transfer trip from Germany to Croatia in Italy on the Autobahn 437. Version GT9 V-Max, that means a very narrow car without a rear wing, only a spoiler lip and 1400 hp with an extremely long gearbox. I am very proud of it. 437. In 2012/2013 it was kind of like shooting, so it was a long time ago. We have been in the speed regions since then. But nothing officially confirmed, I only have the log file of it. Enough for me, I know it was so quick and that is the end of the case for me. To be continued in the second part. .
Cinelecture 87 – Gene Expression in Eukaryotes and Prokaryotes Compared – so we're going to compare gene expression in prokaryotes and eukaryotes by way of review let's start out with prokaryotic gene
expression up until the details of translation anyway so here we have a stretch of prokaryotic DNA that we will define as an operon in operon in prokaryotes is a cluster of genes say gene 1 here gene 2 and gene 3 that are coordinately transcribe that is there's a
transcription unit which which transcribes all three of these
genes at once into one messenger RNA and that messenger RNA is polycistronic meaning that the same messenger RNA is
decoded into three different proteins that is there are three
different genes that are transcribed into 1 mRNA and transcription starts at the plus one site of of the gene we call that plus one is the
start of transcription and you'll notice that their is a start of translation for gene 1 and a stop of translation of gene 1 so we'll say that the stops are in red
here and there is a start of translation for gene 2 and a stop translation for gene 2 and there is a start for translation for
gene 3 and a stop of translation for gene 3 so that in the messenger RNA that is transcribed from an operon there are
coding sequences for 3 different proteins so we
can highlight those as follows: there's one..
there's two and here is three so we have three different protein-coding regions
in the same messenger RNAs and for each one we
have a start and we have a stop that is true for each of these such that translation will begin at the start and translation will stop at the stop
signals when codons for the
stop of translation are encountered now upstream of the plus one transcription
start site there is a sequence of DNA which is
the promoter and it is to the promoter that RNA polymerates binds through mechanisms that we've
already discussed the sigma subunit of the RNA polymerates binds to the promoter loads the polymerase here and as transcription
begins the sigma subunit is released and elongation of the mRNA occurs now upstream of the first translation start
site in the messenger RNA is the five prime untranslated region which contains a sequence.. I'll highlight it thusly contains a sequence in the five prime untranslated region
call the ribosome binding site so in the gene that from which the messenger RNA is
transcribed there is information the sequence in nucleotides
that encodes the ribosome binding site found
in the RNA because the RNA is transcribed from
the gene and ribosome binding site of prokaryotic messenger RNAs is then a sequence of nucleotides called the
shine dalgarno sequence shine dalgarno you'll often hear referred to as that which is the point at which the ribosome will bind and begin translation at the
first starts site in in so that when translation begins and stops begins and stops begins and
stops each in this three gene operon that
I've indicated here each coding region
encoding a different protein… protein 1 protein 2 and protein 3 now what is the advantage of prokaryotes clustering their genes in what we would call an operon and we
can see that an operon is then a cluster of genes which encode
protein which enclude proteins and these
proteins are often involved in running the same biochemical
pathway so if we have a biochemical pathway here where
we can bring with lets say compound A to compound B to compound C to a product of the pathway let's say that this is an anabolic
pathway each of these steps is catalyzed by a particular enzyme enzyme 1, enzyme 2, and enzyme 3 you can imagine then that the three proteins
encoded by this hypothetical operon are in fact enzyme 1, enzyme 2, and enzyme 3 so the advantage of coordinately
transcribing a single polycistronic mRNA and which
coordinately transcribed 3 genes at once is that when
this biochemical pathway needs to run in the
cell we need enzyme 1, enzyme 2, and enzyme 3 to run this biochemical pathway the common messenger RNA will allow for the coordinate expression of these three proteins and
enzyme 1, enzyme 2, and enzyme 3 so the biochemical pathway will run
likewise if transcription is shot off for the
operon we don't need product anymore let's say there's plenty product around transcription of the operon will cease and we shut off the production of the
proteins required to run the biochemical pathway so coordinate regulation by the
production of polycistronic mRNAs is a very efficient way to coordinately regulate gene
products which are involved in a common goal, a
common biochemical pathway now in prokaryotes there is a
single RNA polymerase which as we've mentioned consists of the core enzyme and an associated sigma subunit and the sigma subunit
associates once transcription begins in elongation of the RNA proceeds let's compare that.. one other
feature is that in prokaryotes we have coupled
transcription and translation that is because there is no nucleus
separating ribosomes from the DNA which is being transcribed ribosomes can begin associating with the
messenger RNA even prior to the finishing a transcription
as we've already mentioned so that does not occur in eukaryotes we do not have coupled
transcription translation let's move over here to look at eukaryotic gene
expression and as far as we've covered it so far so here we have DNA and that DNA is transcribed from a plus one transcription start site and we have
messenger RNA produced unlike prokaryotes though these messenger RNAs are monocistronic that is each gene has its own transcription unit is its own transcription unit there is only
in other words one RNA for one protein or possibly more if there's alternative
splicing but there are not multiple genes clustered together and upstream of the plus-one site as in prokaryotes there is also a promoter
to which as we've seen basal transcription
factors bind basal TFs would stand for basal transcription
factors bind which recruit RNA polymerase to the promoter and there are three
different RNA polymerases in eukaryotes 1, 2, and 3 each one responsible for transcribing
different classes in genes and as we've as we talked about so if we are
looking at pol 2 transcription RNA polymerase 2 transcription transcribing genes that will encode
a protein product now one thing I've forgot to mention in prokaryotic gene expression is that in the DNA is a defined site which is a sequence of bases which signals the termination of
transcription so we have transcription termination
site here which at which point transcription of the
messenger RNA ends through formation of a hair pin loop in the formation of a hair pin in the messenger RNA which is dictated of course by the sequence
of nucleotides in the DNA in eukaryotes there's no
well-defined termination site the polymerase
transcribes and eventually will fall off the template DNA releasing the messenger
RNA now for eukaryotic genes there's
also a translation start site and a translation stop site but eukaryotic genes are broken
up into exons here's an exon and here's an intron and here's another exon and lets say here's another intron and then here's the final exon so that the RNA and eukaryotes will be processed by adding a five prime cap five prime cap serves as the ribosomes
binding site unlike the sequence of nucleotides that
defines the ribosomes binding site in the shine dalgarno case where the ribosome binds to a define
sequence of nucleotides in the mRNA of prokaryotes here the five prime caps serves as the ribosome binding site and the five prime cap is added post transcriptionally so
post-transcriptional modification whereas the ribosome binding site in prokaryotes
is part of the messenger nucleotide sequences dictated by the sequence of nucleotides in the DNA we polyadenylate poly a tails are added to the 3 prime end of a eukaryotic messenger RNA so we add poly a tails and we add a five prime cap to the end of the messenger RNA and then of course in addition to these two post-transcriptional
modifications we also have splicing so that the exons present in the messenger RNA exon 3 is here.. are brought together by splicing out of the the introns the introns are spliced out and with these three modifications then
we end up with a messenger RNA as a poly a
tail has a five prime cap and has the exons of the gene join together exon 1 exon 2 and exon 3 now as in prokaryotic messenger RNAs
there's also a five prime untranslated region of eukaryotic mRNAs because the start of translation it will be downstream of the start of transcription so the start of
translation occurs usually in the first exon of the gene of the mRNA and there's also a three prime
untranslated region that occurs after the stop of the the stop site of translation so we've gotten essentially a nice comparison of eukaryotic and prokaryotic transcription and of gene expression up unitl the point of translation and unlike prokaryotic gene expression we do not
have coupled transcription translation in this
case here in eukaryotes we must take the
mature mRNA that is produced by these
post-transcriptional modifications and we must have mRNA export so all these steps leading up to translation are points at
which in both in prokaryotes and eukaryotes are
potential points of regulation of gene expression that we will be considering shortly and so now it's time to move onto translation and that is where we'll be going we'll be looking at both prokaryotic and eukaryotic translation and come to understand how
is that amino acids are specified in a polypeptide chain based on the nucleotide sequences that are present in the codons of mRNAs in prokaryotes and eukaryotes so we'll pick up with translation in the next
part of this lecture .