Why the number of human genes is 3/4 fewer than we originally estimated?Will it be never possible to find a vaccine against HIV?

About the universe,about the earth,about ourselves,there are too much problems for us to discover.But what are the most important ones?How much further were we from the answers?July 1st,in the celebration of the 125th anniversary of the American journal——"Science Magzine",scientists concluded 125 most compelling puzzles and questions which until now we have not been able to answer.the top 25 are most important.

Universe:

1.What is the universe made of?

Someone may bolt out:It's made up of the stars.But in the past several decades,scientists have come to find that wrong.Astronomers think mater,or what we call ordinary matter which makes up of the stars,planets,galaxies and,of couse,us,makes up less than 5% of the total mass of the universe.And they estimate that the other 25% may be dark matter which is made of the particles that we have not yet found.Then,what about the 70% left?Astonomers say it may be dark energy——the force that lead to an accelerated cosmic expansion.What is the hypostasis of dark matter and dark energy?Scientists have been searching for the answers by using accelerator and astronomical telescope.And if the answer is finnally found,the significance is undoubtedly "universe-class".

2.Are we alone in the universe?

45 years ago astonomer Frank Drake launched the first project——Ozma Project,to search for extraterrestrial intelligence(SETI),using large antenna(Radio Telescope) to receive signals from alien civilization.Now 45 years have past,astronomers are still trying hard.But even Project Phoenix,the biggest-ever one,have not found any signals from alien civilization.

Earth:

3.How does earth's interior work?

More than 40 years ago,a revolution in earth science arose.Continental Drifts Theory renewed our knowledge about the earth.But the theory about earth's interior structure is the same as what it was before the revolution.What scientists have done is to complete the egg model,divided it into 3 parts——Crust,Mantle and Centrosphere.By using Seismic Wave Imaging,scientists are now studying on the process of the big machine's work.But maybe we'd have to wait half a century for another revolution.

4.How hot will the greenhouse earth be?

It's sure that the concentration of CO2 will continue to increase,and it's also sure that this increase will result in global warming,but the extent is still not sure.Scientists generally figure that the increase of CO2 in this century will cause a 1.5℃～4.5℃ temperature rise.But it's not precise enough.Scientists are establishing new math model,trying to make the numbers convincible.

Mathematics,Physics And Chemistry:

Can laws of physics be unified?

An apple drop,a lightning across the sky,uranium in the nuclear reactor of a nuclear power plant gives off its energy while disintegrating,super accelerator breaks proton:all these phenomenons represent four fundamental forces in nature——gravitation,electromagnetic force,weak force and strong force.All the physical phenomenons can be explained by using the four fundamental forces.But scientists are not satisfied.Is it possible to unify the four forces?In 1960s,physicists found that weak force and electromagnetic force can be unified,they are different sides of a same thing,we call it electroweak force.But can the other two left be unified together?

6.Do deeper principles underlie quantum uncertainty and nonlocality?

Quantum Theory is more than 100 years old,it has convincible application achievements,but it also brings a reverse intuition:the uncertainty principle pointed out that we can not obtain the momentum and position of an object with precision at the same time.And the nonlocality principle make it possible for the entangled states of two particles in emtanglement to collapse at the same time,no matter how far they are from each other."Quantum mechanics is very impressive," Albert Einstein wrote in 1926. "But an inner voice tells me that it is not yet the real thing."

7.How far can we push chemical self-assembly?

In some sense,chemists are the kind of people who like inventing most,because they always create new molecules.Although nowadays chemists are able to build very complex chemical structure,can they make the job easy and at the same time complicated?That is to say,let the material atoms self-assemble and form a complex structure,just like the kind of self-assembly that life shows.We have some practice now,such as build a double membrane structure like cell membrane.But for more complexity,for example,to build an integrate curcuit from the top down,is still a dream.

8.What are the limits of conventional computing?

There are something in this world that looks easy but hard to solve,for example,if a salesman needs to walk around several cities which connect each other,how can he find a shortest distance?The increase of the numbers of the city would frustrate even the biggest computer.In 40s of last century,Claude Shannon,the father of Information Theory,brought forward the physical laws followed by the information(in form of byte) storage and transmission.Never can a traditional computer go beyond the laws.So in engineering,how strong a computer can we finnally make?However,non-traditional computer may not be astricted by these laws,for example,the recently springing-up quantum computer.

Biology:

9.What is the biological basis of consciousness?

In the 17th century the French philosopher said:"Cogito, ergo sum(I think,therefore I am)".We can see,consciousness has been a philosophy topic for a long time.Modern science considers consciousness emerges from the cooperation of billions of neurons in the brain.But it's still too general.To be specific,how do these neurons give birth to consciousness?In recent years,scientists have found some methods and tools to study the most subjective and most personal subject in an impersonal way,and by observing the patients with cerebral lesion,they have been able to peek the arcanum of consciousness.Besides make clear the way consciousness actually operates,scientists want an answer of a deeper question:why does it exist,and how did it originate?

10.What controls organ regeneration?

Some creatures have amazing ability of self-repairing:a cutted fishworm can outgrow another half of it's body,and newt can rebuild it's injured limbs......By comparison,human's ablility of organ regeneration seems not that good.Nobody can outgrow a cutted finger,so are our bones.What comforts us a little is liver.A partial resected liver can recover to its initial state.Scientists found that those animals,which are able to regenerate their organ,restarted some genetic process of fetation as occasion requires,so they outgrow new organs.Then,in a similar way,is it possible for us human to regenerate our organs under control?

11.How can a skin cell become a nerve cell?

In the middle of last century,biologists put a somatic cell nucleus of a frog into an enucleated egg cell,then created a clone tadpole.In recent years,the research on human embryonic stem cell are undertaking in full swing——putting human somatic cell nucleuses into enucleated human egg cells,scientists expect to produce many kinds of human somatic cells,such as nerve cells,osteoblasts,myocardial cells and so on.Scientists have made some progress,but they still know little about the reason for the success of cell nuclear transfer technology.It's sure that enucleated egg cell plays an important role in the process——then,what is the concrete mechanism?

12.How does a single somatic cell become a whole plant?

In some sense,plants seem more flexible than animals to survive and reproduce.They don't need the complicated process of somatic cell nuclear transfer technique.Scientists have been already using this advantage.By using only a tiny piece of plant tissue,they can grow enough seedings for a forest.But why do plant cells have this kind of flexibility?Scientists have found some clues,for example the effect of auxin in the process.

13.How and where did life on earth arise?

Paleontologists have found fossils of microbes dating back at least 3.4 billion years,photosynthetic organisms were also found on even older rocks.So the two backbones of life——protein and DNA,which appears earlier on earth?A hypothesis considers that life originated from the hot water in deep sea.Now,on the one hand scientists are looking for a way to show the development process from simple organics to organics with the function of self-reproduction,on the other hand,their studying on comets and Mars,will also bring some significant enlightenments.

14.What determines spicies diversity?

This is a planet of countless lives,but not every corner of the world is filled with the same prosperity.Some places have more spicies than the others.Tropic zone shows a higher diversity than frigid zone.Why?Is it only because tropic zone has a higher temperature?Scientists presume,the key is the interaction between lives and the environment.Of course there are other forces to change the diversity,just like the relationship between preyer and prey.But,the chief problem scientists are facing is how to acquire the basic data of the diversity of the world——how many spicies are there on earth?

15.How did cooperative behavior evolve?

It's easy for you to find alruistic behaviors in social animals.For example,a bee would send out information of food to the other bees.Human society and societis of other primates are also full of cooperative behaviors.Founder of Revolutionism,Darwin have explained this behavior to some extent,for example,the cooperation between relations actually increase the possibility of reproduction of the whole family.Nowadays scientists are looking for genetic basis of cooperative behavior.And the game theory——a matematic theory about competition,cooperation and the rules,helps them understand how do cooperative behaviors work.Darwin had once observed this kind of behavior and explained it,but contemporary scientists want a deeper explanation,and hope it would be able to explain how does this kind of behavior originate.

16.How will big picture emerge from a sea of biological data?

Lives are so complex that almost every biologist can only work in a small field.Although each field brings lots of descriptive datum,scientists have been able to form a general idea from them,such as how do lives operate?System biology,which is being forming nowadays,are offering some opportunities to answer these questions.System biology tries to combine the branches of biology and,by using mathematics,engineering and computing science,make biology more quantitative.But no one is sure that these methods can help biologists understand the big picture of lives.

Human:

17.Why do humans have so few genes?

In 2003,when the human genom project were being completing,when all biologists were ready to celebrate the great achievement,they amazedly found the number of genes were fewer than they originally estimated.Yes,human have about 25,000,but the estimated number is 100,000.By comparison,even an animal as simple as a wireworm has 20,000 genes.Arabidopsis thaliana has a few more than us,and rice doubles the number.Scientists presume the way genome works is more flexible and complicate than originally assumed.They are trying to find some molecular mechanism to do more work with fewer genes.

18.To what extent are genetic variation and personal health linked?

Long ago,scientists have found that some patients have different reactions to certain drugs.For example,a certain kind of muscle relaxant for anesthesia will make certain kind of people choke.Finally,scientists found it was because they had certain kind of genes.This brought a problem:will the research on genetic variation among different kinds of people advance the development of medical science and help develop better therapeutic means.That is to say,use medication according to individual DNA.Scienstists have identified some genes which interact with certain drugs.But it's too early to achieve actual individual drug use.

19.How much can human life span be extended?

Although still we can hardly see a centenarian,the average life of human have kept on increasing during the past several decades.For how will the trend continue?Though the research on experimental animals,sientists found they can prolong the animals' life span obviously by using some methods including restrict caloric intake.Can we apply these methods be applied to human?And for how long can they prolong human lifetime?Some scientists presume we can easily live to an age of 100 years old.However,long life will bring some troubles,like this one——social insurance.

20.What genetic changes made us uniquely human?

With the improvement of gene sequencing technology,scientists collected more and more complete genome sequences of varieties of spicies in their database,including human and many primates,such as chimp.We can easily recognize human and chimp,but at molecular level,this kind of differentiation is not so easy to obtain.The difference of DNA between chimps and us is merely 1.2%.It's a tiny number,but it means a difference of more than 30 million base pairs in absolute amount.Which of the 30 million differences on earth made us so unique after the separation of chimps and us?Scientists are trying to find the genetic differences which make us different from the other primates.And,of course,there are some other elements beyond genes,like culture,language,and technology.

21.How Are Memories Stored and Retrieved?

Good memories,bad memories,memories about equation solving,English words......they are undoubtedly storing in our brain.Where exactly they are?

In 1950s,the hippocampus area in the brain plays a very important role in the process of memory storing——if we resect it,the memory of the past will lost.But how do these nerve cells in hippocamus get information fixed.Scientists have found some molecules which participate the memory forming process.Besides,the forming of neuron synapse have relationships with memory forming,too.But the understanding of the operation mechanism of memory still couldn't satisfy the scientists——this mechanism is extremely important for us to understand ourselves.

22.Can we selectively shut off immune responses?

Organ transplantation is not rare in today's surgery,but there still exists the seemingly inevitable problem which doctor and patient needs to face——immunological rejection.The immune system of the patient will probably regard the transplanted organ as an "enemy",and attack it,and the surgery finally fail.To prevent this,doctor have to select the donor organ quite carefully,and for some of the patients,they need to take immunosuppresive drugs for a whole lifetime——obviously,it's not a good idea.Now scientists have found several possible methods to keep the immune system working without rejecting the transplanted organ.But we still need to wait for a long time for the clinical application.

23.Is an effective HIV vaccine feasible?

Every year the U.S. National Institutes of Health alone invests nearly $500 million on the search for a vaccine against HIV.Hitherto none of the vaccines is practically effective.Some skeptics contend that no vaccine will ever stop HIV,they argue that the virus changes too quickly during the process of replication.But the supporters found the vaccines can protect monkeys from Simian Immunodeficiency Virus(SIV),so they believe vaccines for HIV will come true.

24.What can replace cheap oil——and when?

Nobody denies that we will use up oil one day.Moreover,the oil production will probably go down quite soon.Despite these factors,we are impelled to find a substitute for oil by the threatening global warming.Solar power?Wind power?Nuclear power?Each of them has good potential,yet none of them is mature.

25.Will Malthus continue to be wrong?

In 1798,Malthus published his famous book "An Essay on the principle of population",argued that human populations will always tend to grow because it can't catch up with the growth of food supply,only disaster can stop the population growth.Now,200 years have past,we have 6 billion people on the planet,six times the number of Malthus's time,yet happily,the disaster he predicted never happens.To a great extent science prevents the disaster,but the the problem we still need to face——how can we make sure that no catastrophe happens in the future?