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Cloning and Stem Cells

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How are animals cloned, especially mammals? What is the difference between reproductive cloning and therapeutic cloning? What is the difference between embryonic stem ... – PowerPoint PPT presentation

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Title: Cloning and Stem Cells


1
Cloning and Stem Cells
  • How are animals cloned, especially mammals?
  • What is the difference between reproductive
    cloning and therapeutic cloning?
  • What is the difference between embryonic stem
    cells and adult stem cells?
  • What legal and ethical issues revolve around
    cloning and stem cell technologies?

2
Hello, Dolly!
Dolly and her surrogate mother
Dollys lamb, Bonnie
3
Mammalian cloning
4
Somatic nuclear transfer
Totipotency (the ability to differentiate into
all different cell types) was regained when
somatic cells were arrested in the cell cycle
before DNA synthesis.
5
Why has cloning mammals become possible now?
  • In vitro fertilization technology has come of
    age. Louise Brown the first test tube baby was
    born in the 1970s.
  • Nuclear transfer into human eggs is possible for
    males with defective sperm.
  • Embryo transfer is routinely used for
    reproduction of livestock (cattle)

6
How easy (efficient) is animal reproductive
cloning?
  • Dolly was the only lamb from 277 fused eggs
  • Mice, cows, pigs, sheep, cat, monkey, mule
    successfully cloned.

Tetra rhesus monkey
Copycat
Idaho Gem
7
Are cloned animals healthy?
  • Dolly gave birth to a healthy lamb named Bonnie.
  • Dolly was put down because she was suffering from
    premature arthritis and other ailments.

8
What would a human clone be like?
  • A. The clone will not have a mother.
  • B. The clone will be essentially an identical
    twin of the original, offset in time.
  • The clone will have the memories of the original.
  • All of the above.
  • None of the above.

9
Complications in reproductive cloning
  • Cloned offspring syndrome
  • Placental abnormalities
  • Fetus too large
  • High rate of spontaneous abortions
  • Early death
  • Shorter telomeres?
  • Genes not imprinted properly
  • Genes that control placental growth, fetal growth
    inactivated in maternal chromosomes

10
Human development from egg to morula
2-cell
oocyte
4-cell
8-cell
11
Human blastocyst and post- implantation fetal
development
The blastocyst implants into the uterine wall for
further development
5 weeks, 5 mm
9 weeks, 30 mm
12
Cloning to produce embryonic stem
cellstherapeutic cloning
Create a cloned embryo from the patients own
genetic material as a source of genetically
matched embryonic stem cells. Involves
destruction of the embryo to create a stem cell
culture.
13
Q What does the law say about human cloning?
  • A. No legal restrictions.
  • B. Research with human fetal tissues prohibited.
  • C. Research restricted to a limited set of
    pre-existing embryonic stem cell lines.
  • The 13th Amendment prohibits creation of human
    clones.
  • Individual states ban reproductive cloning

14
Alternatives to embryonic stem cells?
  • Adult stem cells
  • Induced pluripotent stem cells
  • Aoi et al. 2008, Generation of Pluripotent Stem
    Cells from Adult Mouse Liver and Stomach Cells,
    Science 321699-702
  • Retroviral vectors used to transduce 4
    transcription factors, incl. c-Myc
    (proto-oncogene)
  • ES-like cells in gene expression profile,
    pluripotency (form tumors containing different
    cell types, form all 3 major tissue types in
    chimaeras, germline transmission)

15
Q Which of these pose ethical issues when
applied to human reproductive cloning?
  • A. Cloning is still inefficient only a few
    percent of somatic cell transfers are successful.
  • B. Cloning requires surrogate mothers
  • C. Human egg donors are required
  • D. Human clones will have the memories of the
    original
  • E. All of the above are ethical difficulties for
    human cloning

16
Q In your opinion, when does a human embryo
acquire personhood, deserving of legal
protection?
  1. At the time of fertilization or nuclear transfer
  2. At the time of first cell division
  3. At the time of implantation into uterus
  4. At 40 days after conception
  5. When fetus becomes viable outside the womb
  6. At birth
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