What is Cloning?
Clones are organisms that are exact genetic copies. Every single bit of their DNA is identical.
Clones can happen naturally—identical twins are just one of many examples. Or they can be made in the lab. Below, find out how natural identical twins are similar to and different from clones made through modern cloning technologies.
How Is Cloning Done?
Many people first heard of cloning when Dolly the Sheep showed up on the scene in 1997. Artificial cloning technologies have been around for much longer than Dolly, though.
There are two ways to make an exact genetic copy of an organism in a lab: artificial embryo twinning and somatic cell nuclear transfer.
1. Artificial Embryo Twinning
Artificial embryo twinning is a relatively low-tech way to make clones. As the name suggests, this technique mimics the natural process that creates identical twins.
In nature, twins form very early in development when the embryo splits in two. Twinning happens in the first days after egg and sperm join, while the embryo is made of just a small number of unspecialized cells. Each half of the embryo continues dividing on its own, ultimately developing into separate, complete individuals. Since they developed from the same fertilized egg, the resulting individuals are genetically identical.
Artificial embryo twinning uses the same approach, but it is carried out in a Petri dish instead of inside the mother. A very early embryo is separated into individual cells, which are allowed to divide and develop for a short time in the Petri dish. The embryos are then placed into a surrogate mother, where they finish developing. Again, since all the embryos came from the same fertilized egg, they are genetically identical.
2. Somatic Cell Nuclear Transfer
Somatic cell nuclear transfer (SCNT), also called nuclear transfer, uses a different approach than artificial embryo twinning, but it produces the same result: an exact genetic copy, or clone, of an individual. This was the method used to create Dolly the Sheep.
What does SCNT mean? Let's take it apart:
Somatic cell: A somatic cell is any cell in the body other than sperm and egg, the two types of reproductive cells. Reproductive cells are also called germ cells. In mammals, every somatic cell has two complete sets of chromosomes, whereas the germ cells have only one complete set.
Nuclear: The nucleus is a compartment that holds the cell's DNA. The DNA is divided into packages called chromosomes, and it contains all the information needed to form an organism. It's small differences in our DNA that make each of us unique.
Transfer: Moving an object from one place to another. To make Dolly, researchers isolated a somatic cell from an adult female sheep. Next they removed the nucleus and all of its DNA from an egg cell. Then they transferred the nucleusfrom the somatic cell to the egg cell. After a couple of chemical tweaks, the egg cell, with its new nucleus, was behaving just like a freshly fertilized egg. It developed into an embryo, which was implanted into a surrogate mother and carried to term. (The transfer step is most often done using an electrical current to fuse the membranes of the egg and the somatic cell.)
The lamb, Dolly, was an exact genetic replica of the adult female sheep that donated the somatic cell. She was the first-ever mammal to be cloned from an adult somatic cell.
How does SCNT differ from the natural way of making an embryo?
Natural fertilization, where egg and sperm join, and SCNT both make the same thing: a dividing ball of cells, called an embryo. So what exactly is the difference between the two?
An embryo's cells all have two complete sets of chromosomes. The difference between fertilization and SCNT lies in where those two sets come from.
In fertilization, the sperm and egg have one set of chromosomes each. When the sperm and egg join, they grow into an embryo with two sets—one from the father's sperm and one from the mother's egg.
In SCNT, the egg cell's single set of chromosomes is removed. It is replaced by the nucleus from a somatic cell, which already contains two complete sets of chromosomes. So, in the resulting embryo, both sets of chromosomes come from the somatic cell.
Is cloning an organism the same as cloning a gene?
You may have heard about researchers cloning, or identifying, genes that are responsible for various medical conditions or traits. What's the difference?
When scientists clone an organism, they are making an exact genetic copy of the whole organism, as described above.
When scientists clone a gene, they isolate and make exact copies of just one of an organism's genes. Cloning a gene usually involves copying the DNA sequence of that gene into a smaller, more easily manipulated piece of DNA, such as a plasmid. This process makes it easier to study the function of the individual gene in the laboratory.
AUTOR: Supported by a Science Education Partnership Award (SEPA) Grant No. R25RR016291 from the National Center for Research Resources, a component of the NIH. The contents provided here are solely the responsibility of the authors and do not necessarily represent the official views of NIH.
DIRECCIÓN WEB: http://learn.genetics.utah.edu/content/cloning/whatiscloning/ (20/08/2014)
KNOW
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LEARNING
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TASK 2: CONNECTISM.
KNOW
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WANT TO KNOW
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LEARNED
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Sabemos que es una nueva teoría del
aprendizaje
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¿Cómo surge esta teoría?
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¿En qué contexto socio-histórico?
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¿En qué época?
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¿Quiénes son los impulsores de esta corriente?
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¿Cuál es la base de la misma y sus
fundamentos?
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¿Qué paradigma sustenta el Conectivismo?
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Es una teoría que considera a la tecnología
como el nexo entre el alumno y el aprendizaje.
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Contiene ocho principios básicos que la caracterizan.
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El texto también nos aporta una visión desde la experiencia.
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El texto nos aporta una imagen donde se
visualiza el Conectivimo a través de todas las interconexiones sociales
(hogar, escuela, comunidad, mundo).
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Otro punto relevante que queremos resaltar con
respecto a ésta teoría es que no favorece la socialización del niño en general.
Señala a las aulas y docentes como
obsoletos…
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Posted on May 18, 2012
Connectivism, introduced in the
mid 2000’s, is an idea based on the premise that knowledge exits within systems
and is acquired by individuals who interact collaboratively within activities
related to that knowledge. Whether you view connectivism as a learning
theory or a “pedagogical view”, the movement has significant connections to behaviorism,congnitivism, and constructivism.
Marcy Perkins Discroll, in her book, Psychology
of Learning for Instruction, defines learning as “a persisting
change in human performance or performance potential…[which] must come about as
a result of the learner’s experience and interaction with the world.”
Connectivism embodies this definition within it’s core principles.
According to Wikipedia, the eight core principles
of connectivisim are:
- · Learning and knowledge rest in differences of opinions.
- · Learning is a process of connecting specialized nodes or information sources.
- · Learning may reside in non-human technology.
- · Capacity to know more is more critical than what is currently known.
- · Nurturing and maintaining connections is needed to facilitate continuous learning.
- · Ability to see connections between fields, ideas, and concepts is a necessary skill.
- · Knowledge that is current is the intent of all connectivist learning activities.
- · Decision-making is itself a learning process.
Connectivism is not really a new
idea, but new technology has given us ways to “connect” or “interact” faster
and more easily. Approaches to teaching and learning are changing as a
result. Project-based
learning and challenged-based
learning are two examples. Another example, theFlat Classroom, founded by Vicky Davis and Julie Lindsay, springs from a
constructivist approach in which the key component is “lowering the wall” of
the classroom through technology so that students are joined virtually to
create a more expansive, collaborative learning environment.
From a social studies teacher’s
perspective, the benefits of this type of global collaboration for my students
are immediately evident:
- · Authenticity of learning – activities are engaging and real-world
- · Abundance of sources – almost limitless human resources including primary sources
- · Interaction within a global community – the world becomes smaller
- · Access – opportunity to explore and learn about different cultures first hand
The following infographic, in my
opinion, is a good representation of the concept. The words active,
relevant, real-world, effective, hands-on, networked, innovative, personal, and
transformative are all apt descriptors. An additional word could be added
to the “openly networked” heading to read: “connected learning
environments link learning in home, school, community, and the world.”
Creative Commons
Attribution 3.0 Unported
My first project for Course 1 of
CoETaIL is a collaborative blog unit that focuses on culture and digital
citizenship. It begins as a collaborative class activity and then expands
into collaboration on a larger scale. The “tweet” of it’s description would be: ”a project
that allows student teams opportunities for research, creativity, and
collaboration with students from around the world.” This will be our
first project-based activity in the next school year and I’m excited to
implement this new unit. Due to its relevance, I’m reposting the unit
plan here.
A final thought about
connectivisim and global collaboration leads me back to the Education Week article, The
Classroom Is Obsolete: It’s Time For Something New. According
to the author, Prakash
Nair, it is an established scientific fact that the current model of the
classroom is obsolete. The author goes on to state the following
elements that successful learning environments must have in order to prepare
students for success in the 21st century:
- · Personalized
- · Safe and Secure
- · Inquiry-Based
- · Student-Directed
- · Collaborative
- · Interdisciplinary
- · Rigorous and hands-on
- · Embodying a culture of excellence and high expectations
- · Environmentally conscious
- · Connections to local community and businesses
- · Globally networked
- · Setting the stage for life-long learning
I feel lucky to be able to work
in an educational environment that is moving in this direction. A
one-to-one laptop environment has availed numerous opportunities and resources
to my students that were not as readily available before. They are
“connected” to the world in an instant. Some teachers worry that
technology will make their jobs obsolete. I disagree. In good
schools, teachers are working carefully to engineer effective and appropriate
learning opportunities that incorporate many of the 21st century educational
elements listed above. “Change is good.” Though cliché, this is a
true statement. Unfortunately, change is often hindered by lack of
financial resources including those earmarked for technology and professional
development. Nonetheless, as Nair points out, good teachers are putting
forth their best efforts everyday to overcome the “limitations” of the
traditional classroom-based schools. Empowering our students to connect,
interact, and collaborate is empowering them for success.
References:
1)
Jump up^ Fry,
Heather; Steve Kerridge; Stephanie Marshall (2003).Understanding Student
Learning. Routledge Falmer. p. 21.ISBN 9780415434645.
2)
Jump up^ Griffiths,
Tony; David Guile (2003). "A Connective Model of Learning: the
implications for work process knowledge". European Educational
Research Journal 2 (1): 56–73.
3)
Jump up^ Connectivism: A
Learning Theory for the Digital Age, International Journal of Instructional
Technology and Distance Learning, Vol. 2 No. 1, Jan 2005.
6)
Jump up^ Siemens,
George; Stephen Downes. "Connectivism
and Connective Knowledge". Retrieved 2009-01-28.
9)
Jump up^ Connectivism:
a new learning theory?, Pløn Verhagen (University of Twente), November 2006.
11)
Jump up^ Connectivism:
Learning theory of the future or vestige of the past?Rita Kop, Adrian Hill.
In "The International Review of Research in Open and Distance Learning,
Vol 9, No 3 (2008), ISSN: 1492-3831"
12)
Jump up^ Foundations
of Educational Theory for Online Learning, Mohamed Ally. In The Theory
and Practice of Online Learning, Terry Anderson, Ed., May 2008.
(Referencias extraídas del enlace con Wikipedia: http://en.wikipedia.org/wiki/Connectivism).
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