Dna question: Scottishinnz maybe?

I see these illustrations in rags like Scientific American, there are some really nice new pieces about DNA and how they are activated or closed off, with methyl and acetalization, opening up the histones or closing them down and such. I wondered, from the images which shows the RNA and such wrapping around the now open DNA stretch, when that process is finished and a new protein is born, what happens to that particular piece of DNA? Does it zipper back together or is it a one track read and then the whole thing chopped up in aptosis?

Originally posted by sonhouse
I see these illustrations in rags like Scientific American, there are some really nice new pieces about DNA and how they are activated or closed off, with methyl and acetalization, opening up the histones or closing them down and such. I wondered, from the images which shows the RNA and such wrapping around the now open DNA stretch, when that process is fin ...[text shortened]... t zipper back together or is it a one track read and then the whole thing chopped up in aptosis?

DNA only uncoils in small sections at a time, and generally only in specific locations. When it's done transcribing RNA it zips right back up again. DNA lasts about 30 years in most cells, meaning that even for a youngstrel like me (28), I'm quite literally a different person than I was as a child!

The RNA, on the other hand, is broken down pretty rapidly in the normal course of things.



[I should explain, for those who don't know, that DNA is transcribed to RNA (specifically messenger RNA, or mRNA), which leaves the nucleus (in eukaryotes) and moves to the ribosome (normally on the rough endoplasmic reticulum). The RNA is translated, in 3-base sections (called codons), by the ribosome, into a protein. Each codon codes for 1 amino acid (the building blocks of proteins). The act of lining up the right amino acids is facilitated by another class of RNA, called transfer RNA, or tRNA.]

Originally posted by scottishinnz
DNA lasts about 30 years in most cells,

Does the DNA slowly degrade or does it degrade suddenly after 30 years causing cell death or does cell death cause the DNA to degrade?
What is it in a cell that wears out over 30 years?

Originally posted by scottishinnz
DNA only uncoils in small sections at a time, and generally only in specific locations. When it's done transcribing RNA it zips right back up again. DNA lasts about 30 years in most cells, meaning that even for a youngstrel like me (28), I'm quite literally a different person than I was as a child!

The RNA, on the other hand, is broken down pretty ...[text shortened]... the right amino acids is facilitated by another class of RNA, called transfer RNA, or tRNA.]

Hey, thanks. I saw those images and tried to fast forward them but wasn't sure which way the thing would go. It seemed to me for things to be efficient, they would have to zipper back together to be made available for something else down the line. So I was right in that projection.

Originally posted by twhitehead
Does the DNA slowly degrade or does it degrade suddenly after 30 years causing cell death or does cell death cause the DNA to degrade?
What is it in a cell that wears out over 30 years?

Mutations degrade DNA, these can happen at any time basically.

Also the telomeres of chromosomes shorten at each replication.

Originally posted by twhitehead
Does the DNA slowly degrade or does it degrade suddenly after 30 years causing cell death or does cell death cause the DNA to degrade?
What is it in a cell that wears out over 30 years?

I'm not sure. I imagine it does with the cell, and the 30 years figure I heard (alas, during my undergrad, years ago) probably represents a half-life.

Originally posted by twhitehead
Does the DNA slowly degrade or does it degrade suddenly after 30 years causing cell death or does cell death cause the DNA to degrade?
What is it in a cell that wears out over 30 years?

As timebombt pointed out, there is a string of nonsense at the end of DNA. Each time DNA is replicated one bit of the string gets snipped off. When you run out of this buffer material the DNA degrades.