Can your DNA change over time?

Question

I know, unless I am mistaken, that the reason that people eventually grow old and die is because when their cells replicate DNA they eventually produce anomalies that cause the body to slowly become weaker and less efficient until it cannot function. My question is, that if our DNA can change and make us weaker and more vulnerable, can it also change to make us stronger and more powerful? For example, if a child were brought up from a very young age to exercise intensely and regularly until their body became very strong and had adapted to having such strain put on it, could that person's cells DNA change by the laws of evolution and such to make their bodies naturally tone and strong even without training. If this is possible, then is it also possible to pass those genes onto their children? And please, only well educated people answer please.

Answer 1

you're pretty much right with your summary of ageing - the signs of ageing are associated with a process called "telomeric degredation", where the telomeres are little structures located in every one of your body's cells. as we all know, cells divide & copy themselves throughout the life span, which is why we shed our old skin/hair etc, and it happens with internal cells as well. when cells divide, the little telomeres inside the cells are actively involved in this process, and after 50 or so years they get a bit tired of constantly dividing. the ends of the telomeres begin to break down, leading to signs of ageing like wrinkles (skin cell telomeres), slowing of the digestive processes (e.g. intestine cell telomeres), etc etc.

DNA mutations can occur at any point in a person's life span, and can affect a person either positively or negatively. however mutations won't be passed on to a person's children unless the mutation occured in the gametes (sperm or eggs). so if a person's DNA mutated to make them extremely athletic or incredibly intelligent, it would not necessarily be directly passed on to their kids because the mutation may not have occured in their s*x cells.

this is why diseases like breast cancer, prostate cancer, polycystic ovarian syndrome and other s*x-cell linked diseases are often genetically linked, because the mutations occur in the gametes.

Answer 2

Eukaryotes:

DNA has something at the ends of it called a telomere. After each round of replication a small portion of DNA is lost. The purpose of the telomere on DNA is to ensure that essential components of DNA are not lost though this process. Over time, regardless of what you do physically, the telomeres will shorten. There is an enzyme that some cells have in more abundance than other called telomerase which extends the length of the telomere on the DNA

Evidence for telomere length and aging can be seen in various aging disease such as Werner syndrome and Blooms syndrome.