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Trends in Biotechnology
Revision Questions
In 2005, ES-like cells were generated
using four factors. The resulting cells
were called iPS cells.
What does iPS mean?
induced pluripotent stem cells =
iPS cells
What are some different
sources of stem cells?
Embryonic stem cells
Nuclear transfer cells
Adult stem cells
Induced pluripotent stem cells
Nuclear reprogramming was
first proved by Sir John Gurdon
in 1962.
What did Gurdon do?
Gurdon generated new frogs by
transferring tadpole intestine cell
nuclei into enucleated eggs from
the African clawed toad,
Xenopuslaevis.
1997, Sir Ian Wilmut's team showed
Dolly the sheep, the first cloned
mammal created using a nuclear
transfer method. Why is this
significant?
It showed that the genome DNA of
mature cells theoretically have all the
information needed to develop
animals, and that this DNA can be
reprogrammed.
In 2001 Takashi Tada demonstrated
that thymocytes acquire pluripotency
upon electrofusion with mouse ES
cells. What does this show?
It showed that ES cells also
contain factors that induce
pluripotency in somatic
cells.
Shinya Yamanaka’s lab identified
many factors that either are
specifically expressed by or have
important roles in mouse ES cells.
What did many of these factors
seem to be?
They were transcription factors.
Which four transcription factors
were essential for developing
pluripotent cells?
Oct3/4, Sox2, Klf4 and c-Myc
How were the genes for the
transcription factors put into
the target cells?
A lentiviral vector.
In 2007 Thomson's lab announced in
Science that they had also succeeded in
making human iPS cells using a different
set of four factors - Nanog, Lin28, Oct3/4
and Sox2.
Later Yamanaka showed that iPS cells can
be generated without c-Myc.
Why was this important?
c-Myc is an oncogene
X-ray crystallography can be used
to find out the structure of
molecules.
If we want carry out a
crystallographic study what do we
need to have?
A crystallized sample of pure protein.
What causes chronic
myelogenous leukemia(CML)?
A chromosomal translocation
creating an abnormal fusion
protein, kinase BCR-ABL, which
signals wrongly, leading to
uncontrolled proliferation of the
leukemia cells.
What is tyrosine kinase?
Tyrosine kinase is a common
signaling molecule that, when
activated, triggers cells to
divide.
In CML, the mutated tyrosine kinase is active for
too long, causing cells to multiply at an
abnormally high rate. This results in the
overproduction and accumulation of immature
white blood cells.
Scientists found considerable
variation in the ATP-binding
pockets of the different kinases.
What does this mean for
treatment?
This meant that a drug that
specifically blocks the bcr-abl ATP
binding site might be possible.
How does Imatinib work?
Imatinib works by preventing a
tyrosine kinase enzyme, in this case
BCR-Abl, from phosphorylating
subsequent proteins and initiating the
signalling cascade necessary for
cancer development, thus preventing
the growth of cancer cells and leading
to their death by apoptosis.
In the 1990s, Andrew Fire and Craig Mello
were studying how gene expression is
regulated in C. elegans. Among other
things, they were examining mRNA that
encodes a protein involved in the
nematode’s ability to move. They injected
the nematode gonads with sense RNA.
What is sense RNA?
A molecule identical to a segment
of mRNA
Fire and Mello injected other
nematodes with antisense RNA that
could bind to the corresponding mRNA
for the muscle protein.
Which RNA caused a major change in
the muscles, sense or antisense?
Neither RNA had much
effect.
When they injected a mixture of sense
RNA and antisense RNA, the nematode
offspring moved in an odd, twitching
fashion. Similar movement patterns
could be seen in nematodes with a
defective muscle protein gene. What
was the explanation for this surprising
finding?
Together, sense RNA and the
corresponding antisense RNA make up
double-stranded RNA, and it seemed as if
this could silence the gene that encoded
the muscle protein.
These RNA molecules control degradation
of mRNA molecules by biochemical
machinery.
What is RNA interference
naturally used for?
Regulation of gene
expression.
Defence against viruses.
Protection against
transposons.