1. Genetic from Mendel to the Era of
Discovery In 1938, when the young North American
geneticist Hermann J. Müller used to work with flies of the
species Drosophila melanogaster, exposed to X rays at the
Edinburgh Animal Genetics Institute (United Kingdom), he
did not foresee the implications that his findings would
have in the molecular biology and genetics in the following
70 years.
in 1983, Barbara McClintock, an
American cytogeneticist and the first
woman to receive an unshared Nobel
Prize in Physiology or Medicine,
hypothesized the existence of a special
structure at the chromosome tip that would
maintain chromosome stability

2. Genetic from Mendel to the Era of

3. Genetic from Mendel to the Era of
He had just observed that the ends of the
irradiated chromosomes, different from the other
genome, did not present alterations such as
deletions or inversions, thanks to the presence
of a protective cap that he called «terminal
gene» and afterwards «telomere», from the
Greek terms «telos» (end) and
«meros» (part) (Müller HJ. The
remaking of chromosomes.

4. Genetic from Mendel to the Era of
According to his theory of telomeres are represented by tandem
repeats, which create a buffer that determines the number of
divisions that a certain cell clone can undergo.
Furthermore, it was predicted that a specialized DNA polymerase
(originally called a tandem-DNA-polymerase) could extend
telomeres in immortal tissues such as germ line, cancer cells and
stem cells. It also followed from this hypothesis that organisms
with circular genome, such as bacteria, do not have the end
replication problem and therefore do not age.
In the early 1970s, Soviet
theorist Alexei Olovnikov first
recognized that chromosomes could
not completely replicate their ends; this
is known as the "end replication
problem"

5. Genetic from Mendel to the Era of
Elizabeth Blackburn and her graduate
student Carol Greider then went looking
for the mechanism that maintains
telomeres, and on Christmas day, 1984,
discovered the first evidence for the
enzyme telomerase. Combining both
protein and RNA components, telomerase
is a reverse transcriptase which adds
telomere DNA to the ends of molecules
using an RNA template.