The document summarizes several studies on DNA replication and the molecular machinery involved. It describes how researchers used tools like molecular biology and biochemistry to slow down and "freeze" the replication process at intermediate steps. This allowed them to observe conformational changes in proteins like the origin recognition complex (ORC) as it recruits the helicase enzyme to unwind DNA. Cryo-electron microscopy was then used to capture 3D structures of the protein components and reveal how they interact during replication initiation. The studies provide new insights into this critical cellular process.

4.  More complex organisms are composed of
millions of cells, so it is essential to know to
understand the life sciences.
 The formation of the earth began about 4.6
billion years, and from there slowly and step by
step was formed everything we see at this time.
 Humans are composed of more than 200 different
cells, specialized in various functions that enable
the functioning of our body with a set ready to
face a world

5.  The current research picks up where a study
conducted last year left off. That research
determined the structure of a piece of protein
machinery called the "origin recognition complex"
(ORC), which identifies and binds to DNA-
replication "start" sites. When joined by a
replication initiation factor, the ORC undergoes
conformational changes that set in motion the
whole replication process. The new study reveals
how this previous structure recruits and interacts
with the enzyme that eventually unwinds the
DNA double helix into two separate strands.

6.  Catching the molecular machinery in action is no
simple task. Intermediate protein structures exist
on fleeting timescales, and the interactions take
place at the atomic level. Researchers working in
Speck and Stillman's labs used tools of molecular
biology and biochemistry to slow down the
process.
 They purified and then remixed together pieces of
the protein puzzle (including the origin
recognition complex, the replication initiator, the
core of the helicase, and other components) and a
slow-acting energy agent so the energy-requiring
reaction is unable to proceed to completion.

7.  Like dancers paused in place by a sudden stop of
music, the molecular components "froze" partway
through the helicase recruitment/assembly
process.
 Jingchuan Sun at Brookhaven then literally froze
the samples, embedding them in ice, and took tens
of thousands of pictures with a cryo-electron
microscope. He then used computer software to
reconstruct the 3-D structure from the 2-D
electron microscope pictures.

8.  Comparing the new structure (components of the
helicase bound to the origin recognition complex)
with the structures of the ORC produced last year
revealed conformational changes. Binding of the
helicase core components appears to shift the ORC
into a spiral conformation that closely matches the
spiral shape of double-stranded DNA.

9.  It is really wonderful as they could observe the
behavior of these proteins, as well as took benefit
for subjects such as cell division can currently
serve in the treatment of many diseases.
 Also, is very important how each of the people
committed to the struggle for finish work research
and thus show excellent results, which are not
easy but not impossible.

10.  The answer, says Dr. Mak in research published
today in the Journal of Experimental Medicine, is
found in the way estrogen rushes in to "rescue"
cells whose healthy functioning has been altered
by oxidative stress, a well-established factor in
cancer development. Without estrogen, these
damaged cells would die a natural death and not
threaten the host in the long run, but with
estrogen, these cells not only survive, but thrive
and develop breast and ovarian cancers. In
Canada, about 1,000 women die from BRCA1-
related cancers every year.

11.  The research published today illuminates the
interplay between the tumour suppressor gene
BRCA1 and a master regulator -- Nrf2 -- that
governs the antioxidant response in cells. In
healthy cells of all tissues, BRCA1 normally
repairs damaged DNA in partnership with Nrf2,
and so the cells are protected against oxidative
stress. However, when the BRCA1 gene is
mutated, it loses its ability to repair DNA and can
no longer partner with Nrf2, shutting off its
antioxidative function.

12.  In most tissues, the resulting oxidative stress kills
the cells that have lost BRCA1 function. However,
in breast and ovary, the estrogen present in these
tissues can swoop in to rescue BRCA1-deficient
cells by triggering a partial turn-on of Nrf2. These
unhealthy cells gain just enough resistance to
oxidative stress to keep them alive and growing.
Over time, these surviving BRCA1-deficient cells
accumulate more and more mutations due to their
lack of ability to repair DNA damage, eventually
leading to the development of cancer in these
tissues.

13.  The missing piece of the puzzle was estrogen and
its unexpected effects on the antioxidant
regulation mediated by Nrf2.
 The research published today was funded by
grants from the Canadian Institutes of Health
Research, the Ontario Ministry of Health and
Long-term Care, and The Princess Margaret
Cancer Foundation.

14.  At present, the breast and ovarian cancer affects
many women in the world, because this is very
important, that prove predisposition forms in
order to "prevent“.
 However, this study goes into an ethical and
society, because it can be a way to prevent cancer,
but also pitted against a world that makes facile
way to deliver it to the youth especially, is very
difficult.

15.  At this time, medical advances from all eyes but
likewise advancing disease, so if you want to
promote health, we find every day a new thing so
that way we can work with the prevention and
treatment of all the various conflicts that appear
every day.

16.  In a medical career will always find puzzles to
solve, issues to investigate and to clarify doubts.
all these studies being conducted continuously
help us make our work simpler and we
understand there are also advances in all areas
 Doctors face daily with diseases easily spread in
the population, and yourself from terminal
characteristics for life, for this, do research and
learn about these is not far from reality, and never
left over any issue that has to do with these

17.  Be aware about new treatment options and
disease prevention, serves not only to learn, and is
reflected in dealing with the sick and the way it
seeks the welfare for all, this is the reason which
the doctor has to study all his life.
 also, is of outstanding importance to know about
more concurrent diseases in the population, so to
be clear, also need to know about every part of our
body and its functioning.

18.  Daily, in a medical career and in many others, we
have to face anything new coming out every day,
for this, it is useful to establish contact with the
daily news that is reflected in our knowledge.
 Not only important for the medical, also helps to
enrich our language and our way of life, which are
required to complete a professional.

19.  Editorial Staff. Science Daily, you source for the
latest research news [revista en Internet][citado
2013 Jul 16]. Disponible en:
http://www.sciencedaily.com/releases/2013/07/130
714160514.htm
 Editorial Staff. Science Daily, you source for the
latest research news [revista en Internet][citado
2013 Jul 16]. Disponible en:
http://www.sciencedaily.com/releases/2013/07/130
715105118.htm
 MARTINEZ SÁNCHEZ, Lina María. Biología
Molecular. 7. Ed. Medellín: UPB. Fac. de
Medicina, 2012. 7-8 p.