RNA and AA, how do they become us?


So, I understand RNA uses DNA as a template to later code for amino acids, and these AA form polypeptide chains, etc. But- is RNA all there is to following and carrying out DNA’s instructions? The analogy I was taught is that DNA is a sort of protected master copy.

In other words, can every unit of matter that we are, essentially, without environmental factors, be created through the AAs RNA produces? This would also include any AA that coded for something that could produce something else essential down the line. I’ll give an example I keep thinking of- so humans have the character of hair. Our DNA would normally* code for that (sorry bald ppl). So in the case of hair, would RNA then create a polypeptide that would result in hair follicles, growth, keratin production, etc?

I’m not sure if this made sense, but, yeah, help!


In: Biology

So, your protein’s primary sequence is the amino acids. So the DNA codes for RNA which codes for an AA sequence.

But that’s not all there is to proteins, there are things called post-translational modifications which happen to proteins. This will modify the protein by adding on sugars, cutting off sections, creating cross-links, sulphonating Tyrosines and others.

If you were to take some of your DNA for a single gene and put it in a different organism, the post-translational modifications would be different, so it would end up being slightly different. To make it completely the same, you’d need to change a huge amount of DNA.

Other parts of your body which aren’t made of protein are created by enzymes. So you have proteins which act as chemical reactors and cause certain chemical reactions to happen, creating other chemicals which make up your body. These enzymes are ultimately encoded by your DNA, though.

You also have things which you cannot make which make up your body. Vitamin D is created by sunlight when it’s source chemical is in your skin. Vitamin C cannot be made by humans any longer, as our common ancestor with other primates lost the gene to make it. So we need to eat it.

Metals like Iron, Calcium, Sodium and Potassium are also critical to the functioning of your body. You can’t make these from DNA, you can only consume them!

You also have things which you can’t make from scratch with DNA, only expand and divide. So your outer cell membrane can’t be created from DNA alone, you need to have a cell membrane already! Then you can add to it and then the cells can divide. But you don’t have any gene which lets you create a cell membrane from scratch. The same applies to the mitochondria which live inside your cell. They have their own DNA and a double-cell membrane. You can’t create those from scratch either.

All cells with a nucleus contain a complete copy of the genome, during development our cells differentiate to become different types of cells through expression of certain genes and turning off others in response to some chemical signal. In the case of the hair on your head those cells would differentiate in development to express genes that are responsible for production of keratin, etcetera. This would be produced in the way you described sometimes referred to as the central dogma of biology: DNA is transcribed into RNA which is then translated into amino acids which constitute proteins.

If you’re asking if RNA can be used by itself and bypass DNA, the answer is yes! Although it’s generally not desirable.

There are tons of viruses that don’t use DNA at all, only RNA.

Even more relevant is the [RNA world hypothesis.](https://en.wikipedia.org/wiki/RNA_world) This is a theory that the earliest forms of life used RNA, before DNA had even evolved into existence.

Generally, though, RNA is much less stable than DNA, so it runs the risk of corrupting or losing information much faster than DNA, which is likely why evolution settled on the double-stranded variant for long-term storage.