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DNA Modifications Change As We Age
sciencehabit writes "As we age, the core of our biological being — the sequence of our DNA, which makes up our genes — remains the same. Yet recent research suggests that more subtle chemical changes to our DNA occur as we age. Now, a comparison of the DNA of a newborn baby with that of a centenarian shows that the scope of these changes can be dramatic, and they may help explain why our risk of cancer and other diseases increases as we get older."
No more adept at biology, but I read that the replication is most susceptible to errors at the ends, which is why there are chunks of non-coding DNA (telomeres) there which get shorter with each replication.
What the article is discussing is how methylation differs between very young and very old people. The abstract of the original paper may be more instructive:
Human aging cannot be fully understood in terms of the constrained genetic setting. Epigenetic drift is an alternative means of explaining age-associated alterations. To address this issue, we performed whole-genome bisulfite sequencing (WGBS) of newborn and centenarian genomes. The centenarian DNA had a lower DNA methylation content and a reduced correlation in the methylation status of neighboring cytosine—phosphate—guanine (CpGs) throughout the genome in comparison with the more homogeneously methylated newborn DNA. The more hypomethylated CpGs observed in the centenarian DNA compared with the neonate covered all genomic compartments, such as promoters, exonic, intronic, and intergenic regions. For regulatory regions, the most hypomethylated sequences in the centenarian DNA were present mainly at CpG-poor promoters and in tissue-specific genes, whereas a greater level of DNA methylation was observed in CpG island promoters. We extended the study to a larger cohort of newborn and nonagenarian samples using a 450,000 CpG-site DNA methylation microarray that reinforced the observation of more hypomethylated DNA sequences in the advanced age group. WGBS and 450,000 analyses of middle-age individuals demonstrated DNA methylomes in the crossroad between the newborn and the nonagenarian/centenarian groups. Our study constitutes a unique DNA methylation analysis of the extreme points of human life at a single-nucleotide resolution level.
what I understand from that wall of text is this: The paper puts forward is another factor that contributes to errors cropping up causing diseases associated with old age, like cancer. Methylation controls (or should that be retards?) transcriptional activity, so a change in methylation patterns, or a drop in the occurence of methylation, would change the types of activities the DNA undergoes, and change the probability (probably upwards) of things going wrong.
I am but a lowly undergrad who doesn't pay as much attention is lectures as he should, so please someone correct me if I am wrong.
It means that although the DNA will remain the same, how it is transcripted into proteins (and how often, and in reaction to what stimuli) changes. That is the purview of epigenetic study (the epi- prefix meaning over or above). Here's a useful link.
Epigeneric drift is not changes of the sequence of genes just their expression. In their example genes are surpressed by the presence of methyl groups attached to some parts of the DNA molecule.
So what you're saying is that our DNA has split ends?
So we need DNA's version of Head and Shoulders then?
This was falsified several years ago when it was shown that retrotranspons alter the sequence of DNA in each cell dynamically continuously. Not only that, but cells are altered differently, so a person's cells diverge as they age. The paper is usually paywalled but I have a copy thanks to the generosity of the authors, if anyone wants a copy.
Sorry, but as a matter of principle I automatically reject any claim that has as its central tenant a theory that has already been falsified. Keep up or keep the hell out.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Biology is by far my weakest science and I'm not qualified at all to comment, but I just read two articles today which suggests that older fathers have longer lived children...
Here and here.
It sounds like Pak Protectors. In his version of reality the age based changes originally had a purpose. The fact there's a genetic change matches with his scenario. Just interesting how science fiction and reality often converge.
A lowly undergrad who bothered to read and think about the article.
BURN HIM!
The changes outlined refer to methylation, not to actual dna change. The sequence is the same as when you were born (for most part), but methyl groups attach to certain genes to turn them off and detach from other ones to turn them on. This stuff isn't passed to offsprings, they're just switches that are placed on the dna. So, it turns out the old people have the genes that increase chance of cancer/diabetes turned on while babies with the same genes have them turned off, and a middle aged adult is in between.
This is fairly interesting discovery. I guess the next step is to figure out what's controlling the methyl groups. The whole field of biology is enormously complex, there are so many variables and they are all somehow interrelated. Programming analogy: It's like spaghetti code and the program is running exclusively on global variables where each variable controls multiple functions. It runs very efficiently and fast, but debugging is a nightmare. To make matters worse you can't even see these molecular structures in action even under a microscope because they're way too small, so it's like trying to debug the executable of the aforementioned program without a disassembler... the only tool biology has: is the ability to modify the executable and run it again to see what it does. It's amazing that we came to understand this much with our primitive tools.