If the human genome contains about 30K genes,how can our cells make many times that # of different proteins?

Question

Isn't each gene responsible for the synthesis of one specific protein?

Answer 1

A gene can be transribed, to produce mRNA, in various reading frames. Whilst there's only one start codon (AUG), introns can be spliced out in a variety of ways.

For instance, take the sequence "CGTAAGCCT", which intersects the downstream splice site. It could be spliced out as: "TAA GCC T", or it could, alternatively, be spliced out as "AAG CCT". This shift in reading frame can have a huge impact on the amino acid sequence that's transcribed: giving rise to a whole new protein.

Besides changes in the reading frame caused by alternative splicing, sections of the intron may, or may not, be incorperated into the protein.

So, the old dogma "one gene for one protein" is, perhaps, a little too simplistic; althrough it's still true for prokayoyotes.

Answer 2

You are right to say that one gene gives you one protein. But for a gene to be transcribed, there are several factors that you need to take into account. If the factors are not achieved, the gene would not be transcribed. This is why NO cells are transcribing 30k genes. They are only transcribing genes that they are "told to be so".

Take for example Insulin, only the beta cells in the Islet of Langerhans produces them, you don't see our skin producing insulin every now and then. This practically shows that there is no way a cell can transcibe 30k genes. Even if it can, the cell requires a gigantic amount of energy and it would probably have died along the way.

Transcription of genes require transcription factors, coactivators, activators, signals, Polymerase, nucleotides, primers and promoter +++. Signal is the first step. So, if there is no signal, there is no transcription. This means that in our cells, there is NO way 30k different signals can come in and "ask" for a transcription for all the genes. You will also need the other factors and it is almost impossible to gather so much nucleotides and transcription factors for the cell.

So the bottomline is, there is no way a cell can make 30k genes. Each species of cell produces its required protein and they are controlled by signals produced from our body.

Answer 3

Just to add to what's already been said...

One gene does (generally) encode one protein, but alot of things can happen even after the protein has been translated. Such "things" are called post-translational modifications that can splice proteins and sometimes alter their folding patterns, which can in turn alter a protein's function. These alterations have nothing to do with the gene itself, but these (along with the other explanations given above) account for the great diversity of proteins in the human body.

Answer 4

Well proteins are just made from different combinations of amino acids. There are a total of 20 different amino acids, and so to make a protein, you just need to know which one goes where.

You know a potato has over 100k genes? It's not the number of genes, but how complex they are.

There are billions of bases in your DNA. It only takes 3 to code a single amino acid.

30k genes may not sound like much, but they are all extremely complex genes

Answer 5

Your question seems to stem from what you believe to be a disconnect between # of proteins in a cell vs. number of genes. Your cells do not have more than 30,000 DIFFERENT types of proteins, so you may be confusing # of proteins total with # of distinct proteins.

You are right that, in general, 1 gene = 1 specific protein (of course numerous copies made from one mRNA strand).

This means that each gene can be transcribed to make several mRNA molecules and each mRNA can be used to make several (if not dozens) specific proteins. One gene = one mRNA = many copies of identical proteins.

Answer 6

Human DNA incorporates the counsel for many many distinctive proteins yet they're expressed at distinctive stages in distinctive cellular and subsequently some proteins are contemporary in one form of cellular yet absent from yet another which does no longer require it. think of of the internet, the comparable counsel is obtainable to all people yet in step with all people (like each cellular) they gets admission to distinctive information superhighway pages (proteins) than yet another person. wish that enables and that analogy replaced into concept up very immediately so please do no longer poke holes :)

Answer 7

Inside of genes are stretches of noncoding sections called introns. During the transcription of DNA, the introns are removed prior to actual transcription. By removing different segments, RNA polymerase can create a variety of different genes from the same section of DNA. That's one of the theories...

Answer 8

Alternative splicing:
http://en.wikipedia.org/wiki/Alternative_splicing