Telomeres protect the genetic information by multiple methods. First, as cited below, DNA polymerase cannot replicate the ends of the chromosome. DNA polymerase is actually “too large” to stay on the single-stranded overhang of DNA that is left and literally falls off the end of the chromosome. There are biochemical and electromagnetic reasons it separates. When it leaves the chromosome end, it has not completed replication of that portion of the DNA. An unreplicated DNA end is considered “uncapped” which would turn on the “DNA damage response” and cause the cell to commit suicide – known as apoptosis. The telomeric segment of the chromosome is the “end cap”, since it falls back over in itself and never allows the repair and damage pathways to see an “uncapped” DNA strand. To the damaged pathways, it looks like a complete double-stranded end of fully replicated DNA.
The second known way it protects: The uncapped ends of a DNA strand are subject to recombination with other uncapped DNA strands, causing genetic aberrations and instabilities that may lead to mutations. This actually does happen when the telomeric segment becomes too short. Some cancers use this method to lengthen their chromosomes and avoid the DNA damage response, which would otherwise kill the cancer cell.
A common mistake I see in answering this question: telomeres do not contain “genes” or any genetic material in the classical sense at all. They consist of six different deoxynucleic acid molecules in repeating sequence, which does not code for anything so far as we know at this moment.
The next mistake I see and hear often is that certain products lengthen telomeres. Only TA-65 has any human data and has a completed human trial reported in Rejuvenation Research. The data from the second part of that trail is due for release shortly and is very positive. With regards to ANY other product as of this writing: that is not true in humans because no other products have completed any human trials. One product has one source for laboratory data that, when repeated by another lab, gave two different results. The first repeated result was negative for telomerase activation and the second was weakly positive compared to TA-65, but again, these were lab trials, not human. I do not know if that information will be published yet.
The information about telomeres/telomerase and telomerase activators and inhibitors is always growing and sometimes changing so, in a year, some of what has been said above may no longer be accurate; but as of today it is.