Download cloned - humancloning

Producing an exact genetic duplicate of an organism.
•Bacteria, Yeast and Plants
- “Like, since forever”
CLONING
ANIMALS
Frogs
•1952, frogs cloned via transfer of nuclei
from early tadpoles into enucleated frog
eggs (Robert Briggs & Thomas King)
•1962, frogs cloned via transfer of
nuclei from later tadpoles into
enucleated frog eggs (John Gurdon)
CLONING
Mice
•1977, Clement Markert and then Hoppe & Immensee
produced a series of reports through 1982 of mice
“cloned” by removal of the male pronuclei from a
newly fertilized egg, followed by stimulation of the
female pronucleus to divide (now diploid).
Parthenogenesis: reproduction from an
unfertilized ovum
CLONING
Mice (continued)
•1983, McGrath & Solter (and many others) could NOT
repeat work of Markert, Hoppe & Immensee but
demonstrated that they could “efficiently” produce
mice by nuclear transfer if there was one “male”
(sperm-derived) pronucleus and one “female” (ovumderived) pronucleus.
Parthenogenesis: NOT POSSIBLE
CLONING
Mice (continued)
•1983, McGrath & Solter (continued)
Gynogenotes: (Diploid Maternal) NOT POSSIBLE,
none survived to term; embryos had only minor
aberrations but supporting tissues were stunted
Androgenotes: (Diploid Paternal) NOT POSSIBLE,
none survived to term; embryos were puny and
poorly developed but supporting tissues were nearly
normal
CLONING
Imprinting: Because the DNA sequences in the
chromosomes of the gynogenotes, androgenotes, and
normal embryos produced by nuclear transfer were the
same (inbred mice used), it was concluded that the genes
had somehow been modified or imprinted differently
during gamete production (maternal or paternal origin).
Male and female gametes’ nuclear genetic contribution to
the embryo is equal quantitatively but not qualitatively.
Genes expressed only by the paternal contribution are important to
placenta development and genes expressed only by the maternal
contribution are important for embryo development (at least in mice).
CLONING
Gene Cloning
•1971-1973, The first recombinant DNA experiments
involved the joining of DNA from SV40, a virus that causes
tumors in monkeys, with the genome of a bacterial virus
called lambda.
Lambda infects E. coli, which is found in
mammalian intestinal tracts.
- Recombinant DNA experimentation severely restricted by NIH.
Cloning
- 1979, Restrictions on recombinant DNA relaxed.
- 1978, Birth of Baby Louise, the
first child conceived through in
vitro fertilization.
- 1983, First human mother-mother
embryo transfer.
Cloning
- 1985, First transgenic
livestock, pigs that produce
human growth hormone.
- 1985-1990, Embryo cloning of livestock.
16-cell blastocyst, each cell totipotent and capable of
developing into a whole organism.
Cloning
- 1990, BABI used for prenatal
diagnosis.
- 1993, Cloning of human
embryos. Jerry Hall of
Washington University split a
“defective” human blastocyst
Human Blastocyst
and documented development
of the individual “clones” to the 32-cell stage before
destroying them. (He lost his NIH funding.)
Cloning
•Higher animals carry out a sex-specific genomic imprint
(programming) during gamete formation.
•After the 16-cell stage of development cell-specific
genomic programming occurs as the cells differentiate
into the various cell types of our bodies.
1996
“Cloning of higher animals not possible until
we understand both the sex-specific genomic
imprint and the cell-specific genomic
programming.”
Cloning
•Higher animals carry out a sex-specific genomic imprint
(programming) during gamete formation.
•After the 16-cell stage of development cell-specific
genomic programming occurs as the cells differentiate into
into the various cell types of our bodies.
1996
“Cloning of higher animals not possible until
we understand both the sex-specific genomic
imprint and the cell-specific genomic
programming?”
Cloning
Sheep
- February, 1997
Ian Wilmut and Keith Campbell from the Roslin
Institute in Edinburgh, Scotland reported (Nature)
the “cloning” of a sheep (Dolly) by transferring the
nucleus from an udder cell of an adult ewe into an
enucleated egg.
Cloning
The trick behind the Roslin team’s success was to
make the donor cells behave more like the inactive
DNA of a sperm or unfertilized egg.
Accomplished by “starving” them into the
dormant G0 or G1 stages of the cell cycle.
“Starving” or serum deprivation is known to cause
many genes to “shut down”. At the same time, the
genome apparently becomes “reprogrammed” in the
environment of the enucleated egg, so that the cell
becomes totipotent (tissue-specific program erased).
The gametic sex-specific imprint must remain.
Cloning
• July 1997, Transgenic cloned sheep (5) were produced by
nuclear transfer from cells carrying the human factor IX
(hemophilia B) gene.
• October 1997, Headless frog embryos produced.
- Jonathan Slack, at Bath University in England,
created frog embryos without heads. He
speculated that sometime in the future, organs
grown through nuclear transfer, followed by
strict control of developmental pathways (i.e., to
make headless clones), might provide
compatible transplant material.
Cloning
Headless human clones for transplant donors?
• Lewis Wolpert, a developmental biologist and chair of
the Royal Society’s Committee on the Public
Understanding of Science (COPUS) asked, “If the donor
is never sentient to begin with, what could be the harm.”
• Wouldn’t “headless” clones be the functional equivalents
of anacephalics (currently, 1 in 500 live births; a polygenic
or multifactorial genetic disorder that occurs in a
female/male ratio of 3/1)?
Cloning
• January 1998, Charlie and George, two transgenic
(human factor IX) “cloned” male Holsteins were
produced.
• …….mice, goats, more sheep, more cows……….
• Dolly: 1 in 277 attempts; gave birth; “old” telomeres
• Cloned cow dropped dead seven weeks after birth
(severe anemia; withered thymus; defective donor cell
gene?); 30-50% of cloned calves die shortly before and
immediately before birth.
• Mice: 3 live mice in 274 attempts, two died
immediately after birth, the other had mild breathing
problems.
Cloning
Does human early development allow time for
reprogramming?
Cloning
Does human early development allow time for
reprogramming?
• Mammalian species exhibit many subtle differences with
respect to:
- the timing of division of the developing embryo,
particularly during the first few days,
- time and extent that egg proteins and mRNAs are used.
> sheep: DNA expressed at the 8-cell stage
> mice: DNA expressed at 2-cell stage
> humans: DNA expressed at 4-cell stage
Cloning
• How should human cloning be regulated?
• How many human genes can an animal have before it has
human rights?
• How many animal genes can a being have (e.g., a
humonkey) before it no longer has human rights?
Cloning
Clone 82472
Clone 362436
Perfect for July 4th
or Bastille Day
Ph.D. Clone
She’ll keep
you on track
Clone 321006
Let him help you
with your French
Make an offer
$1,000,000 but willing to deal
Priceless but
available for
weekends.
Make an
offer.