The Mitosis: Steps/Stages of cell division

Interphase	(VIDEO: allez en bas de page: Scroll down) a step : a stage : une étape    The cell is engaged in metabolic activity. It is preparing for mitosis (the next four phases that lead up to and include nuclear division). Chromosomes cannot be clearly identified the nucleus, although a dark spot called the nucleolus may be visible. The cell may contain a pair of centrioles (or microtubule organizing centers in plants).
Prophase	Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres.
Prometaphase	The nuclear membrane dissolves: It's the beginning of prometaphase. Proteins attach to the centromeres: It creates the kinetochores. Microtubules attach to the kinetochores and the chromosomes begin moving.
Metaphase	Spindle fibers align the chromosomes along the middle of the cell nucleus. This line is referred to as the metaphase plate. This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome.
Anaphase	The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Motion results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules.
Telophase	Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei. The chromosomes disperse and are no longer visible under the light microscope. The spindle fibers disperse, and cytokinesis (= The partitioning of the cell) may also begin during this stage.
Cytokinesis	In animal cells, cytokinesis results when a fiber ring (composed of a protein called actin around the center of the cell) contracts. That contraction pinches the cell into two daughter cells, each with one nucleus.  ANIMATION :

WORKSHEET: MITOSIS ANIMATION #1

Mitosis is like a dance!

I. Introduction: a step = a stage ( = a phase)

There are ______ steps which are called “______________________________________________

____________________________________________________________________________.”

II. The steps explained:

1. First, the key is a C_____________ in which there's a C_____________ composed of a C___________________ and a C__________________ !

Make a sketch here:

1. Then, there is a phase called “_________________” because the cell prepares.
   During this phase, the membrane around the N___________ , called “ N____________ M_______________”.
   The membrane ______________ _____.
   The C______________ become more compact ( = more C_____________ ) and
   the C________________ move to opposite ends ( = poles).

Make a sketch here:

2. Next, there's a new phase which is a M_____________ phase called “_______________ because the C____________ line up or meet in the M____________ of the C___________. The C______________ still are at the opposite ends and the S__________ F____________ attach (or link) the C____________ to the P__________/opposite E_______.

Make a sketch here:

3. After that, there's a phase called “________________” because the different elements are A______________. Now the F___________ become shorter and as a consequence, the C________________ go to the P_______________.

Make a sketch here:

4. Finally, the last phase called “________________” starts, which means T__________ because the division takes place. The separation is a process and is also called “C__________________S”. The cell gets bigger before it can split in two!

Make a sketch here:

Racism: Inborn or Acquired?

Tout savoir sur le cerveau! Clique ici (en français)

NEUROSCIENCE/// By Jeffrey Kluger Thursday, Oct. 09, 2008

The human brain is surely the most sophisticated data-processing machine in the world, except when it's not. (...) Like all other animals, our species emerged in a world where there was critical value in distinguishing between members of your own tribe--who nurture you and protect you--and members of other tribes, who see you as a competitor for food and mates. Your very survival can turn on making this distinction quickly. (...)

L'amygdale ou complexe amygdalien est un noyau pair situé dans la région antéro-interne du lobe temporal au sein de l'uncus, en avant de l'hippocampe et sous le cortex péri-amygdalien. Elle fait partie du système limbique et est impliquée dans la reconnaissance et l'évaluation de la valence émotionnelle des stimuli sensoriels, dans l'apprentissage associatif et dans les réponses comportementales et végétatives associées en particulier dans la peur et l'anxiété . L'amygdale fonctionnerait comme un système d'alerte et serait également impliquée dans la détection du plaisir.

Tout savoir sur cette petite partie du cerveau que l'on appelle l'amygdale, clique ici.

In the 1990s, psychologist and social scientist Mahzarin Banaji of Harvard University co-created what's known as the implicit-association test (IAT), a way of exploring the instant connections the brain draws between races and traits. (...) The IAT asks people to pair pictures of white or black faces with positive words like joy, love, peace and happy or negative ones like agony, evil, hurt and failure.

Speed is everything, since the survey tests automatic associations.

When respondents are told to link the desirable traits to whites and the undesirable ones to blacks, their fingers fairly fly on the keys. When the task is switched, with whites being labeled failures and blacks called glorious, fingers slow considerably, a sure sign that the brain is struggling.

When Banaji, along with cognitive neuroscientist Liz Phelps of New York University, conducted brain scans of subjects using functional magnetic resonance imaging, they uncovered the reasons for the results. White subjects respond with greater activation of the amygdala--a region that processes alarm--when shown images of black faces than when shown images of white faces. "One of the amygdala's critical functions is fear-conditioning," says Phelps. "You attend to things that are scary because that's essential for survival."

Later studies have shown similar results when black subjects look at white faces.

-o-o-o-

Phelps conducted other studies in which the images included such friendly faces as Will Smith's and Harrison Ford's and found that this helped control the amygdala too. "The more you think about people as individuals," she says, "the more the brain calms down." (...)

Animal brains operate mostly in the present and past; they know what's happening now, and they recall things that occurred before. When animals encounter an unwelcome outsider, simply driving away the interloper is thus sufficient, since they don't give much thought to whether the intrusion will happen again. Humans, however, operate with awareness of the future, which means we seek to extinguish not only a current threat but also future ones--and that can mean trying to eradicate the entire group that poses the perceived danger.Worse, as our ability to develop weapons has progressed, our ability to carry out our murderous plans advanced along with it. 

 

The bad news is that wisdom, the human faculty that trumps all this, can be very slow to arrive. The good news is that with enough time, both individuals and the species as a whole do acquire it.

Adapted from: http://www.time.com/time/magazine/article/0,9171,1848769,00.html

Le cerveau humain est le résultat d'un longue évolution! Et elle n'est pas terminée, il nous reste à évoluer!