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Introduction to Human Cloning

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Title: Introduction to Human Cloning


1
Introduction to Human Cloning
  • TIP 2
  • Group C
  • CLFS620 Modern Molecular Genetics

2
Focus Questions
  • Answer these questions as you view the Power
    point.
  • 1. What is cloning?
  • 2. What are the 3 types of human cloning?
  • 3. Compare and contrast therapeutic
  • cloning and reproductive cloning.
  • 4. What are ESC? What are sources of ESC?
  • 5. Give an example of the usage of each of
  • the 3 types of human cloning.

3
What is Cloning?
  • CLONING is the creation of a copy of a gene or an
    entire organism using DNA
  • from an existing individual, so that the copy
    has the same genetic makeup as the original
    biological entity.

4
What is Human Cloning?
  • Human cloning is the creation of a genetically
    identical copy of an existing, or previously
    existing, human.

5
Potential uses of cloning
  • Replacing organs and other tissues
  • Infertility aid
  • Treatment of human diseases
  • Creating donor sources
  • Gene therapy
  • Reversing the aging process

6
Different Types of Human Cloning
DNA Cloning Therapeutic Cloning Reproductive Cloning
also called gene cloning or recombinant DNA produces copies of genes or segments of genes the transfer of DNA pieces from one organism to a self-replicating genetic element also called embryo cloning produces a cloned embryo to create embryonic stem cells cloning for the use of studying human development and treating disease the type of cloning that produces a genetically identical human from another human
7
  • DNA Cloning

8
What is Gene (DNA) Cloning? (recombinant DNA)
  • Recombinant DNA transfer of a DNA fragment of
  • interest from one organism to a
  • self-replicating genetic element,
  • such as a bacterial plasmid.
  • The DNA is then propagated in
  • the foreign host cell.

9
Basic Steps of Gene Cloning
  • 1) Restriction enzymes are used to cut a fragment
    of DNA containing the gene to be cloned.
  • 2) Fragments of the foreign DNA are inserted into
    plasmid vectors cut open with the same
    restriction enzyme or one which produces a match
    end.
  • 3) DNA ligase seals the two DNA strands together
    to produce a recombinant DNA molecule.

10
Basic Steps of Gene Cloning
  • 4) The vector transports the gene into a host
    cell (usually a bacterium).
  • 5) Within the host cell the vector multiplies,
    producing numerous identical copies not only of
    itself but also of the gene that it carries.
  • 6) When the host cell divides, copies of the
    recombinant DNA molecule are passed to the
    progeny and further vector replication takes
    place.
  • 7) After a large number of cell divisions, a
    colony or clone of identical host cells is
    produced. Each cell in the clone contains one or
    more copies of the recombinant DNA molecule. ?
  • The gene is cloned.

11
Uses of DNA Cloning
  • 1. Isolation of a particular gene, part of a gene
    or region of a genome
  • 2. Production of a desired RNA or protein
    molecule in large quantities
  • 3. Increased production efficiency for
    commercially made enzymes and drugs
  • 4. Modification of existing organisms so that
    they express a trait not previously encoded
  • in the genome (transformation)

12
Uses of DNA Cloning
13
  • Therapeutic Cloning

14
What is Therapeutic Cloning?
  • Therapeutic cloning refers to the medical
    procedure by which stem cells are harvested and
    grown to mature into transplantable organs or
    tissues.
  • Creates new identical copies of an
  • organisms cells using their own DNA

15
Therapeutic Cloning
  • Basic Principle
  • Performed by removing healthy adult cells from a
    patient
  • reprogramming the cells nuclei
  • collecting and growing embryonic stem cell clones
    from the resulting blastocyst
  • and inducing these embryonic stem cell clones to
    differentiate into the stem cell or mature cell
    types required for transplantation.

16
  • Therapeutic Cloning is also called
  • Nuclear Transplantation or
  • Somatic Cell Nuclear Transfer (SCNT)

17
SCNT Process
  • Step 1 Remove the nucleus from an unfertilized
    egg cell (A) while using a suction pipette (B) to
    hold the egg cell steady and a glass needle (C)
    to remove the cells nucleus.
  • Step 2 Gently push the glass needle through
    the tough shell that surrounds the egg cell. The
    glass needle is used to remove the nucleus from
    within the egg.

http//www.pbs.org/wgbh/nova/sciencenow/3209/04-cl
on-nf.html
18
SCNT Process
  • Step 3 The egg cells nucleus (A) has been
    released outside of the egg. This nuclear
    material will no longer be needed.
  • What remains is an enucleated egg (B). The
    enucleated egg contains certain molecules and
    other important factors that will help to
    establish embryonic stem cells.
  • Step 4 Inject the nucleus (red arrow) from a
    donor cell into the enucleated egg cell by easing
    the tip of the glass needle deep into the
    enucleated egg cell and depositing the donor
    nucleus.

19
SCNT Process
  • Step 5 After completing the nuclear transfer,
    the unfertilized egg cell is activated using a
    chemical or electrical treatment that stimulates
    cellular division.
  • The first division results in two cells (left
    image), the next makes four cells, and so on,
    producing an embryo.
  • Step 6 The proliferating cells form a structure
    called a blastocyst within days, which is roughly
    the same size as the egg cell.
  • Cells taken from the blastocyst are embryonic
    stem cells (ESC).

20
Embryonic Stem Cells (ESC)
  • are not implanted into the uterus
  • are used to study development
  • may be mixed with chemicals to
  • help the cells take on different properties
  • ultimately may be able to
  • introduce these cells into an adult
  • (therapeutic cloning)

21
Embryonic Stem Cells can be cultured in different
laboratory environments to develop into a
specific cell type.
Liver cells
Nerve Cells
Culturedembryonicstem cells (developing an ESC
line)
Muscle Cells
Different types ofdifferentiated cells
Different cultureconditions
22
Embryonic Stem Cells (ESC)
  • Embryonic stem cells (ESC) are cells that have
    yet to differentiate
  • Unspecialized cells
  • Under certain conditions, can be induced to
    become cells with specific functions (heart
    muscle cell, lymphocyte)
  • Sources of ESC
  • 1. Adult Stem cells
  • 2. In-vitro fertilization
  • 3. Umbilical Cord Blood
  • (Core Blood) Stem cells

23
Adult Stem Cells
  • Adult Stem Cells
  • Somewhat differentiated cells
  • Can develop into certain tissues, but not
    necessarily all tissues in the body
  • For example Blood stem cells can develop into
    RBCs, WBCs, but not muscle cells
  • Can be extracted from adults Ex. from bone
    marrow sample
  • Does Not
  • require the
  • creation of
  • an embryo

24
Adult Stem Cells
You can also find these same type of stem cells
in the blood system Peripheral Blood Stem
Cells (PBSCs) Used to treat leukemia, other
cancers and various blood disorders Less
invasive than collecting bone marrow, but are
sparse!
The bone marrow is the spongy core found in the
bones and is a source of adult stem cells.
These stem cells are the precursor cells
responsible for the formation of the blood cells
(red blood cells, platelets, and white blood
cells).
25
What is in Vitro Fertilization (IVF)?
  • IVF is the process of fertilization by manually
    combining an egg and sperm in a laboratory
    setting
  • Similar process to in-vitro fertilization
  • (test-tube baby), except embryonic
  • stems cells are not implanted into
  • mother

26
In vitro fertilizationSome procedures involved
with IVF manually inject the sperm into the egg,
and others simply allow fertilization to occur by
adding the sperm to the egg in the lab setting.

27
Why use IVF as a source of stem cells?
  • According to a survey conducted in 2003, there
    are approximately 400,000 unwanted pre-embryos in
    the United States.
  • (Hoffman, D.I., et al. 2003. Cryopreserved
    embryos in the United States and their
    availability for research. Fertility and
    Sterility 79 1063-1069.)
  • These may no longer be needed for fertility
    purposes and remain frozen or could be destroyed.
  • They may be used in therapeutic cloning (without
    being implanted into a uterus).

28
Umbilical Cord Blood Stem Cells
Multipotent stem cell rich blood found in the
umbilical cord has proven useful in treating the
same types of health problems as those treated
using bone marrow stem cells.
In 2005, there were more than 1,400 cord blood
transplantations in adults, according to NETCORD,
an international network that coordinates
umbilical cord blood banks.
29
Differences between embryonic stem cells and
adult stem cells -ESC can differentiate into any
cell type (totipotent/pluripotent), while adult
SC have already committed to a particular fate
(multipotent).
Some Challenges in Research -Adult stem cells
are often present in only minute quantities and
can therefore be difficult to isolate and purify.
-There is also evidence that they may not have
the same capacity to multiply as embryonic stem
cells do. -They do not have the development
potential of an ESC. -Finally, adult stem cells
may contain more DNA abnormalitiescaused by
sunlight, toxins, and errors in making more DNA
copies during the course of a lifetime. -These
potential weaknesses might limit the usefulness
of adult stem cells.
30
Therapeutic Cloning Potential Application
  • Repair a damaged tissue or group of cells that
    can't heal itself.
  • This might be accomplished by transplanting ESCs
    into the damaged area and directing them to grow
    new, healthy tissue.
  • It may also be possible to coax stem cells
    already in the body to work overtime and produce
    new tissue.
  • To learn more about the causes of
    disease/improved research capabilities
  • Tissue/Organ transplants
  • Potential solutions for currently incurable
    degenerative diseases, like cancer
  • Substitute case for testing new drugs

31
  • Reproductive Cloning

32
What is Reproductive Cloning?
  • Making new, genetically identical copies of an
    organism, by using its own DNA
  • Could possibly create an identical twin,
    born years later

33
Process of Reproductive Cloninghttp//cmgm.stanfo
rd.edu/biochem118/images/Stem20Cell20Slides/082
0Cloning20Procedures.jpg
34
Reproductive Cloning
  • DNA originally from a mature somatic cell is
    added into an empty oocyte (egg).
  • Once the egg has developed into an early-stage
    embryo inside a test-tube, it is implanted into
    the womb of an adult female animal.
  • A cloned animal does not always look identical
    to the original animal.

35
What Animals Have Been Cloned?
  • Mice Cows
  • Sheep Chickens
  • Cat Deer
  • Dog Horse
  • Mule Ox
  • Pig Rabbit
  • Rat Rhesus
  • Monkey Humans???

Ex. Dolly the Sheep (1996)
36
Efficiency of Reproductive Cloning
  • Reproductive Cloning is a very inefficient use of
    technology.
  • There are low success rates in the practice of
    cloning.
  • More that 90 of cloning attempts fail to produce
    viable offspring. The cloning of Dolly took 276
    attempts.
  • Also, more than 100 nuclear transfer procedures
    could be required to produce one viable clone.
  • Some studies show that after 60 cycles of cell
    division, stem cells can mutate and lead to
    cancer.
  • Source http//www.ornl.gov/sci/techresources/Huma
    n_Genome/elsi/cloning.shtml

37
Risks of Human Cloning
  • Cloning tends to produce more compromised immune
    function and higher rates of infection, tumor
    growth, and other disorders.
  • About 30 of all clones born alive are affected
    with large offspring syndrome and other
    debilitating conditions.
  • Clones show premature aging and have shorter life
    spans.
  • Also, there is no known facts on how cloning
    could impact mental development.
  • Sources http//www.ornl.gov/sci/techresources/Hum
    an_Genome/elsi/cloning.shtml

38
Ethical Issues of Human Cloning
  • -- Could allow for manufactured children with
    desired traits and characteristics
  • -- Unrealistic expectations of the clones
  • similarity to the cloned individual
  • -- Could allow for the cloning of a deceased
  • individual
  • -- May violate values of individual freedom,
    identity, and autonomy
  • -- Requires destruction of human embryos in a
    test tube

39
Comparing Therapeutic and Reproductive Cloning
  • Therapeutic cloning
  • Made in the same way as reproductive cloning
    except the embryo is not implanted in a uterus
  • Donor embryos are killed when stem cells are
    harvested from the embryos
  • The stem cells are used to grow different types
    of tissues
  • Reproductive cloning
  • Made in the same way as reproductive cloning with
    the embryo being implanted into a uterus to
    nurture a living individual
  • Donor embryos are killed during the process.
  • Cloned individuals have shorter lifespans and
    possible immune system malfunctions.

40
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41
Acceptable or Not to the Public?
DNA or Gene Cloning Acceptable
Therapeutic Cloning Acceptable with reservations Embryos are destroyed by stem cell extraction.
Reproductive Cloning Currently not Acceptable to clone humans
42
Works Cited
  • Cloning. The National Human Genome Research
    Institute. cited 28 Apr 2009. Available from
    http//www.genome.gov/pfv.cfm?pageID25020028
  • Cloning in Focus. Genetic Science Learning Center
    at the University of
  • Utah. cited 26 Apr 2009. Available from
    http//learn.genetics.utah.edu/units/cloning/
  • Perspectives. 2003. Center for Genetics and
    Society. Human Genetics in the Public Interest.
    cited 1 May 2009. Available from
    http//www.genetics-and-society.org/perspectives/s
    cience.html
  • Reproductive Cloning. Center for Genetics and
    Society. cited 26 Apr 2009. Available from
    http//geneticsandsociety.org/article.php?id282
  • Therapeutic Use of Cell Nuclear Replacement
    Therapeutic Cloning.
  • Medical Research Council. cited 26 Apr 2009.
    Available from http//www.reproductivecloning.ne
    t/therapeutic_cloning.pdf
  • United States Department of Energy. Office of
    Science. Cloning Fact Sheet. May 2009. Human
    Genome Project Information. Available from
    http//www.ornl.gov/sci/techresources/Human_Genome
    /elsi/cloning.shtml
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