The document discusses the importance of DNA replication for life and medicine. DNA replication is essential for cell division and is targeted by chemotherapy drugs to stop the growth of cancer cells. Understanding DNA replication better through research could help develop preventative treatments for diseases and improve medical knowledge.

1. Alejandro Cardona Echandia
Molecular Biology, Faculty of Medicine
2015
Replication of the Genetic Material in
Eukaryotes and Prokaryotes

3. EJERCICIOS

4. Introduction
• The replication of the genetic material is
process that is conceptually simple but
molecularly complicated, from which a DNA
mother molecule is synthesized in a new one,
creating two DNA daughters molecules, with
identical sequence of the original.
• Occurs in coordination with the cell division, in
the S phase of the Cell Cycle.
For the
REPLICATION,
the cell will
need…
• DNA Polymerase
• DNA ligase.
• Topoisomerase.
• Helicases, primases.
• RNAsa H.
• Okazaki fragments.
• Single Stand DNA Binding Protein.

5. ABSENCE OF TUMOR-SUPRESSING
GENE DERILS DNA REPLICATION,
LEAVING
CELLS VULNERABLE TO CANCER
 Cell duplication and growth is essential to
sustaining life, and in order for this critical
function to take place, cells must unwind
the tight ball of DNA in their nucleus and
then duplicate their genomic information.
 This is a delicate maneuver, ripe for errors
or omissions, and if PTEN, a known tumor-
suppressor gene, has mutated or is absent,
the replication process derails and can
lead to cancer development.
“PTEN enzyme structure”
Date: July 7.
Source: Weill Cornell Medical College

6. PTEN is a tumor suppressor . It acts as a dual
specificity protein phosphatase:
•Dephosphorylates phosphorylated proteins on
tyrosine , serine and threonine residues
•Lipid-phosphatase:
•Uses Mg as a Cofactor.
It is critical for tumor suppressor
function.
In the late-1990s, scientists discovered the PTEN gene and growing evidence has
shown that PTEN is a powerful tumor suppressor. Less clear, however, was
whether and how PTEN works when it comes to DNA replication — and if loss of
PTEN could impact this central process of genome transmission to allow
development and progression of cancer.

7. "Tumors without PTEN are more
sensitive to chemotherapies that work
by targeting DNA replication, while
normal cells or cancers with active
PTEN resist these treatments," said Dr.
Wen H. Shen.
Each year about 14
million people globally
are told they have
cancer and 8 million
die from the disease
Each year about 14
million people globally
are told they have
cancer and 8 million
die from the disease
Dr. Wen H. Shen
“Our study shows that PTEN acts as a
guardian of this process by sitting
right on the replication fork to recruit
other essential protective partners,"
she said. "Without PTEN, this
protection machinery falls apart. DNA
is then unprotected, which leads to
fork stalling and failure to restart."

8. PTEN function is absent in a wide variety of
cancers — for example, 70 percent of
prostate cancers have PTEN mutation or
deletion. Because of this, researchers are
currently testing PTEN to see if it's a marker
of aggressive cancer and for personalized
cancer treatment.
"Patients whose cancers have lost PTEN or
harbor mutations in the gene are known to
have poorer outcomes than patients with
active PTEN," Dr. Shen said. "Our expectation
is that a PTEN blood test in the near future
will help clinicians decide on the right
therapies for each cancer patient, and in
particular, to benefit this subgroup of cancer
patients carrying PTEN mutations."

9. Personal Opinion
I think that the future of the actual Medicine is going to be focused in part of the molecular biology and
biochemistry, because each more time, new diseases are emerging with problems in micro-molecular
structures, so its time to consider it as a very important part of science and try to intensify more in them.
Otherwise, for me it’s very important to continue investigation about this enzyme, because, pitifully, cancer
in killing thousands of people every year, and we are face to face with a possible solution for this disease.

10. BACTERIA USE DNA
REPLICATION TO TIME KEY
DECISION
In spore-forming bacteria, chromosomal
locations of genes can couple the DNA
replication cycle to critical, once-in-a-lifetime
decisions about whether to reproduce or form
spores.
Like most microorganisms, Bacillus
subtilis bacteria are single-celled creatures
with one goal: to reproduce by making copies
of themselves.
Date: July 9.
Source: Rice University.

11. But survival isn't always that simple. For example, when
food gets scarce, B. subtilis must decide between two
possible paths: shut down, form a dormant spore
("sporulation") and wait for better times or split into two
cells and gamble that there is enough food for at least
one more generation.
But that decision is one of the most important for
the bacteria. because "If the organism waits too
long, it can starve before it finishes transforming
into a spore. If it acts too early
and forms a spore too soon,
it can be overwhelmed and
out-reproduced by competitors."
said Oleg Igoshin .

12. "Successful sporulation requires two complete copies of the bacterial chromosome,
so coordination between the sporulation decision and the completion of DNA
replication is very important," Narula said.
B. subtilis is harmless to humans, but some dangerous bacteria like Bacillus anthracis, the
organism that causes anthrax, also form spores by a similar mechanism.
B. Anthracis B. Subtilis
"A good analogy might be a
semester-long course in biology.
Lessons are presented in a particular
order, and students are tested after
they learn. If the final exam were
given in the first week, students
would almost certainly fail."

13. To divide and reproduce, bacteria must make a duplicate
copy of their DNA. Because replication of circular bacterial
DNA always initiates at one particular point, Narula
surmised that the location of the KinA (green) and Spo0F
(purple) genes could be crucial. If one were located near
the point where DNA replication began, the cell would
contain two copies of that gene -- doubling the rate of
production of that protein -- throughout the DNA
replication period. If the other gene were located on the
part of the circle that was copied last, the ratio of KinA to
Spo0F would be one-to-one only when DNA replication
was nearly completed.
 "We found that the relative location of
sporulation genes on the DNA circle were similar
in more than 30 species of spore-forming
bacteria, including Bacillus anthracis," Igoshin
said

14. Personal Opinion
I think that we should pay attention on the conclusion that the Dr. Igoshin said at the final of his article,
because it could be very useful at the time that we are going to attack some on the pathologies that we find
actually. How he said, the variability of the bacteria's depends of the place that the DNA replication starts,
so, in the future, we can find inhibitors for the majority of those DNA fragments and counteract much of
pathogens that we could find, making treatment even better and more effective.

15. IMPORTANCE AND UTILITY
OF DNA REPLICATION FOR
MEDICINE AREA
First of all, we have to recognize
de importance of the DNA
replication for life, not only for
human survival also for the other
kingdoms that need it. Because, if
our DNA didn´t get replicated, we
wouldn´t have cell division and
cycle will be interrupted and the
cell would die.
DNA replicates semi-conservative
manner, DNA molecules daughters
will always be an old and a new
chain of nucleotides that contain
all the biological information in the
body.

16. This is useful in treating many diseases, thanks to cell cycle become worse in the case
of cancer and tumor cells. And precisely this is the target of many drugs and
treatments which the patient is provided, in the case of chemotherapy , all with the
aim to curb the growth of cells that do so much damage to the body.

17. But we can not just based on a
curative medicine , preventive
medicine can be the salvation
for many of the diseases that
can be prevented or early
treatment may prevent these
worsened.
For example, It has already been
shown that the preventive
treatment of some diseases
such as certain cancers, tumors
or accelerated cell growth may
be inhibited with certain foods ,
vitamin supplements or drugs in
their default.

18. Promote research and investigation in
medicine basic areas, such as cell biology,
molecular biology, biochemistry and
pharmacology, with the aim of expanding
medical knowledge and implement
humanity solutions from each area of
knowledge.

19. REFERENCES
1) Martínez Sánchez, Lina María; Vargas Grisales, Natalia; Mejía Cardona, Laura;
Osorio Ospina, Felipe; Ramírez Pulgarín, Sergio. “Biología Molecular”. 8va Edición.
Medellín. Colombia. Editorial Universidad Pontificia Bolivariana. Pp: 101 - 108.
2) H. Shen, Wen; Andreopoulou, Eleni; Iadecola, Costantino; Stefan Worgall,
Anne Moore. “Absence of Tumor-Suppressing Gene Derails DNA Replication,
Leaving Cells Vulnerable to Cancer”. Weill Cornell. July 7 2015.
http://weill.cornell.edu/news/news/2015/07/absence-of-tumor-suppressing-
gene-derails-dna-replication-leaving-cells-vulnerable-to-cancer.html.
3) Narula, Jatin; Kuchina, Anna; D. Lee, Dong-Yeon; Fujita, Masaya; M. Süel,
Gürol; Oleg A. Igoshin. "Bacteria use DNA replication to time key decision:
Bacterial decision circuit makes use of circular chromosome." ScienceDaily.
ScienceDaily, 9 July 2015.
<www.sciencedaily.com/releases/2015/07/150709162428.htm>.
4) Images retrieved from www.google.com.

20. In each medical act must be present respect for
the patient plus ethical and moral concepts; then
consciousness and science are always on the
same side, the side of humanity.
(René Gerónimo Favaloro)