Question

doubt :?

Answer 1

Hey Heena.. what's your question?

Answer 2

what do mean by RNA world?

Answer 3

Well basically (as I understand it) its the theory that RNA is actually older than DNA, so it formed first. As in RNA formed the basis of life and then DNA formed.

Answer 4

ok now my main doubt is how DNA comes to exisistence and replace rna and became itself as genetic material

Answer 5

Hmm well (just using my logic) I would suspect that DNA would be able to "survive" and "replicate better" so those forms of RNA with DNA/starting DNA traits would survive better and reproduce more and so the more stable DNA molecule would come into existence (think natural selection).

Answer 6

Also the RNA would be really unstable and so would have alot of mutations.

Answer 7

well i think so too but dont u think if rna si previously working as gentic material then it should continous its process as i just read gene never get changed or consumed when we put it in reaction

Answer 8

Hmm I'm not sure I understand what you mean..

Answer 9

Some cells began to evolve modern metabolic processes and out-competed those with older forms of metabolism.
Up until this point, life had probably relied on RNA for most jobs. But everything changed when some cell or group of cells evolved to use different types of molecules for different functions: DNA (which is more stable than RNA) became the genetic material, proteins (which are often more efficient promoters of chemical reactions than RNA) became responsible for basic metabolic reactions in the cell, and RNA was demoted to the role of messenger, carrying information from the DNA to protein-building centers in the cell. Cells incorporating these innovations would have easily out-competed "old-fashioned" cells with RNA-based metabolisms, hailing the end of the RNA world.
DNA contains instructions. RNA copies DNA. Proteins are made from copies instructions.

Answer 10

i mean i just studied that its the charachter of gene that when we put it into reaction it neer get changed or consumed right so now id although DNA comes in exisitence still rna should work as gentic material y it change its functioning :?

Answer 11

neer=*never

Answer 12

Hmm welll think about this - through the millions of years of natural selection the genes have come to a stage where its a "charachter of gene that when we put it into reaction it never get changed or consumed ". This is because stability would be selected for in natural selection - does that make a little more sense? :)

Answer 13

@kunims@gmail.com still my qn is same gene never get affected then how can we relate by the functioning of cell means it can be true nowadays we are breathing from nose but due to evolution it might dat we will not breathe from nose as new organ introduced?

Answer 14

ok if we say abu stability i gues we can say in the ans right? becoz makes sense like as we found more stable thing we give prior to them but what will happen to the previous stable thing it dosent mean it will change its functioning as it founf other stable thing ?

Answer 15

Well no, but say you have "stable thing" and "more stable thing", the "more stable thing" would be more likely to reproduce. It would then start to outcompete "stable thing" and "stable thing" would reproduce less. Eventually "stable thing" would probably be lost altogether as the "more stable thing" would have better fitness.

Answer 16

but atleat it should perform smthng i mean nowadays rna functioning i totally changed i didnt read abu mutation yet but can we say that if rna perform genetic material by chance or say exception is thi possible?

Answer 17

Herm, sorry you have lost me again, could you rephrase that?

Answer 18

i mean i didnt studied mutation yet so dunno wat actual happens in that but rna as previously work as a genetic material nowadays its performing other function so is their any possibility that rna can work as genetic material nowadays too as a negligible amount but still works like that? becoz i dont agree due to geting more stable sthing stable thing will change its functioning :?

Answer 19

Well yes, of course RNA can work as genetic material too - I mean think about viruses. Hmm not sure how to explain the last part though..

Answer 20

hmmm.. just a querry in my mind dat how can evolution force the rna to change its functioning :P i mean tis torture :P anyways thnQ guys for being here :D

Answer 21

blue plz be quick i have to post one more qn...

Answer 22

These are all very good points. To get everyone on the same page:

Trance is right: the RNA world hypothesis has it that when life first emerged, there was only RNA. In this scenario, RNA both stored genetic info and by folding into higher structures performed functions like catalysis.

The thing is, RNAs are not as dynamic as proteins: if you look at an energy surface of all the conformations a catalytic RNA can assume, they are really limited by constraints placed on them by highly energetically favourable base pairing interactions to limited conformations which don't involve disrupting those base pair interactions. As a result, the types of reactions they can catalyse and the types of other functions they can perform are really limited.

Proteins don't have this problem. They have much broader free energy surfaces; that is, they can assume many more different conformations and have much broader dynamic and functional ranges.

In the opposite direction, DNA is a much stabler molecule than RNA. Because the strands base pair with each other rather than with themselves, they are much stabler molecules and much better suited to long term storage of info than RNAs.

Evolution favours efficiency. Proteins and DNA both provide a competitive advantage over RNA for the reasons stated above, so organisms with proteins and DNA it tended to out compete organisms with just RNA.

RNA clearly has retained its role as a messenger molecule between DNA and protein. It has also retained some of its catalytic and noncoding functions, but these are much reduced and less essential than they were when RNA did everything.

Similarly - and so recently discovered and unsettling to established biologic thought that it is not yet in the textbooks - RNA has also retained some of its info storage function too. In the last six months or so, scientists have discovered so called "heritable RNA" which is duplicated along with DNA and passed to daughter cells during successive rounds of cell division. The function of this heritable RNA is unknown and a subject of much current interest.

I apologize for the length but I hope that clears up some confusion. :D

Answer 23

Oooooo so much beautiful knowledge..

(oops I can't spell)

Answer 24

When they get around to publishing about heritable RNA, it'll be the cover of Nature that week.

Answer 25

Wonderful!!

Answer 26

i knew this the last para that was my doubt now its clear it means it can be happen that rna also get tranformed as genetic material :) thnQ so much blues and all guys :D

Answer 27

You're welcome, any time. :D

Answer 28

No worries :D

Answer 29

one more doubt just hold on m posting dem