Download Biotechnology - York University

Biotechnology
Stem cells
SC/NATS 1840, Biotechnology
1
Biotechnology
z
An inclusive definition of biotechnology is
human intervention with life processes to
produce effects for human benefit.
z
These interventions go back to the beginnings of
civilization.
SC/NATS 1840, Biotechnology
2
Early Biotechnology
z
z
z
Domestication of animals and selective
breeding.
Selection and preservation of seeds and the
deliberate planting of crops.
Organisms used in food preparation and
preservation:
z
z
Bacteria to cause fermentation for beer & wines
Yeast for bread and beer.
SC/NATS 1840, Biotechnology
3
1
Crop rotation
z
Though they did not know it, ancient
practices of crop rotation improved
agricultural yields by releasing organisms that
fixed atmospheric nitrogen in the soil.
z
The ancient Greek botanist Theophrastus said
that broad beans left magic in the soil.
SC/NATS 1840, Biotechnology
4
Microorganisms and Cells
z
z
Progress in biotechnology
depended on our
understanding of life
processes that occur
below the level of
ordinary human
observation.
A technological invention
was necessary:
z
The microscope.
SC/NATS 1840, Biotechnology
5
The Microscope
z
1st invented at the end
of the 16th century
(about the same time
as the telescope)
z
z
Originally the compound
(2 lens) microscopes
were very poor.
The best microscope
was the single lens
apparatus of Anton van
Leeuwenhoek.
SC/NATS 1840, Biotechnology
6
2
The Microscope, 2
z
Van Leeuwenhoek discovered a multitude of living things too
small to be seen with the naked eye:
z
z
z
Spermatozoa
Other single-celled animals
The single-lens microscope is so difficult to use that little
research was done by other people.
SC/NATS 1840, Biotechnology
7
The Cell
z
Compound microscopes became practical in
the 1820s and were the standard research
tool by 1830.
z
German scientists Schleiden and Schwann
observed animal and plant cells and declared that
cells were the units of life.
SC/NATS 1840, Biotechnology
8
The Nucleus
z
Later research in the
19th century identified
the importance of the
nucleus in each cell.
z
z
Discovered chromosomes
in each cell nucleus that
divide and reproduce
themselves with each cell
division.
Chromosomes are thought
to probably carry the key to
cell structure and
inheritance.
SC/NATS 1840, Biotechnology
9
3
Genetics
z
z
In 1865, the monk Gregor Mendel
published the results of his 8-year
study of breeding varieties of
garden peas.
Mendel’s work pointed to the
existence of units of heredity that
operated in pairs and were passed
on unaltered from generation to
generation, but reconfigured into
different combinations in each
individual.
10
SC/NATS 1840, Biotechnology
The Gene
z
In the 1920s T.H. Morgan identified Mendel’s units
of heredity (now called “genes”) as locations on
chromosomes.
11
SC/NATS 1840, Biotechnology
The Gene
z
z
The search for the
gene focused on
the chromosomes,
which are made of
protein and DNA.
In 1944, work done
by Oswald Avery
strongly suggested
that the genes lay
in the DNA.
SC/NATS 1840, Biotechnology
In 1953 James Watson and
Francis Crick worked out the
molecular structure of DNA.
12
4
DNA
z
z
DNA is one of 2 nucleic
acids – acids found only in
the nuclei of cells of living
creatures.
DNA (deoxyribonucleic
acid) has a two strand,
helical structure, with a
sugar-phosphate backbone
on the outside and pairs of
bases on the inside holding
the structure together.
13
SC/NATS 1840, Biotechnology
DNA
z
The bases are Guanine,
Adenine, Cytosine, and
Thymine (referred to by
their initial letters, G, A,
C, T).
z
z
Cytosine-Guanine bond
Guanine always pairs with
Cytosine
Adenine always pairs with
Thymine
Thymine-Adenine bond
SC/NATS 1840, Biotechnology
14
RNA
z
z
z
The other nucleic acid is RNA (ribonucleic acid).
RNA is found in the nucleus but not in the chromosomes.
RNA comes in more than one form, but all have the
structure of a single sugar phosphate backbone and four
bases, Guanine, Adenine, Cytosine, and Uracil (replacing
the Thymine in DNA).
SC/NATS 1840, Biotechnology
15
5
Molecular Biology
z
z
After the discovery of the structure of DNA in
1953, the basics of how DNA contains the
genetic code, how it passes it on to other
cells, and how that code is used to direct the
processes of the body were worked out over
the next 10-15 years.
The two main functions of DNA:
z
z
Self-replication
Sending instructions to the cells
SC/NATS 1840, Biotechnology
16
Self-Replication of DNA
z
z
The DNA makes a copy of itself
every time a cell divides. It does
so by splitting down the middle,
breaking the bonds between the
base pairs.
A new strand forms alongside
each existing strand with the
corresponding base attaching
where the base from the other
strand had been.
SC/NATS 1840, Biotechnology
17
Sending Genetic Instructions
to the Cells
z
z
z
When the body determines that it requires more of something (e.g. a
protein) in a cell, the DNA in that cell opens at the part that has the
blueprint on making the protein.
A strand of “messenger” RNA forms alongside the opened portion of
DNA with the bases that fit against those on the DNA.
The RNA migrates into the cell body and provides a template of
instructions for the construction of the desired protein.
SC/NATS 1840, Biotechnology
18
6
Recombinant DNA
z
z
z
The complexity of DNA has made it very
difficult to study its particular sequences in
detail.
Even a virus can have as many as 5000 base
pairs. A human has more like 100,000 base
pairs in its DNA.
Breakthroughs in research came in the mid1970s with two techniques for working with
DNA.
SC/NATS 1840, Biotechnology
19
Recombinant DNA
z
Cleaving enzymes – that have
the effect of cutting a piece of
DNA wherever it encounters a
certain sequence of bases.
z
z
z
For example the enzyme ECORI
cuts DNA at the sequence
GAATC.
DNA ligases are other enzymes
discovered that rejoin DNA
pieces.
Thus DNA research had the
“scissors” and “paste” tools
necessary to manipulate DNA
and study the results of
experiments.
SC/NATS 1840, Biotechnology
20
Cloning
z
Cloning is the process of producing a strain
of DNA and then inserting that DNA into a
host where it will replicate. The replicated
DNA is called a clone.
z
z
Cloning as a technique has many uses. For
example, it can be used to replicate rare
hormones and proteins such as insulin and
interferon that have much medical usage.
Recently cloning has been taken to far a far
greater extent. Whole organisms have been
reproduced from DNA taken from other bodies.
SC/NATS 1840, Biotechnology
21
7
Insulin
z
Insulin is a protein hormone produced in the
pancreas that the body uses to regulate blood sugar
concentrations.
z
z
z
z
Diabetics have lost the ability to produce insulin and must
have an outside source of it.
In the 1920s, insulin from cows and pigs was isolated and
made available to humans with diabetes. (Though it is not
identical to human insulin.)
Supply was a major concern since the number of diabetics
was on the rise.
Cloning insulin became an ideal usage for recombinant
DNA technology.
SC/NATS 1840, Biotechnology
22
The Manufacture of Insulin by
Cloning
z
z
z
In 1978, Herbert Boyer and
colleagues at the University of
California in San Francisco
created a synthetic version of
human insulin using recombinant
DNA technology.
The DNA sequence representing
the instructions on growing insulin
was separated and then inserted
into the bacterium E. coli.
The E. coli then produced
prodigious amounts of human
insulin.
SC/NATS 1840, Biotechnology
23
The Biotechnology Industry
z
z
z
z
Boyer set up a company to manufacture and sell the
products of Recombinant DNA technology.
His company, Genentech, began manufacturing
recombinant human insulin.
Genentech (stock symbol, DNA) now manufactures
a variety of synthetic hormones for the treatment of
cancer, heart disease, immune system disorders,
and other problems.
A large industry with many companies in many
countries has followed.
SC/NATS 1840, Biotechnology
24
8
Transgenics
z
z
z
A new Green Revolution.
In addition to using Recombinant DNA to
grow hormones and other proteins for use in
the original species from which they came,
the technology has been used to insert genes
from one species into another species
altogether to make a new hybrid that has
desired characteristics.
One of the biggest applications of this today
is genetically modified foods.
SC/NATS 1840, Biotechnology
25
Genetically Modified Food
z
Crops may be genetically modified for a
number of reasons.
z
z
Often the reason is to provide a natural resistance
to insects, making insecticides unnecessary.
Another is to provide tolerance for herbicides, so
that they may then be sprayed on the crops to kill
weeds without killing the crops.
SC/NATS 1840, Biotechnology
26
Genetically Modified Food, 2
z
z
On the left, an ordinary soybean field infested with weeds.
On the right, transgenic soybeans that are herbicide tolerant
after the field was treated with the herbicide.
SC/NATS 1840, Biotechnology
27
9
Genetically Modified Food, 3
z
z
z
Transgenic foods are much more common than one
might think.
Current estimates are that 60-70% of all food sold in
the U.S. contains at least some genetically modified
crop.
The largest crops:
z
z
z
Soybeans – 60% of U.S. crop is genetically altered. Soy
products are ingredients in many processed foods.
Corn – 25% of U.S. crop is genetically engineered. Most of
this goes into corn ingredients in other foods, or as feed to
animals.
Other crops: canola, cotton (as a food in cottonseed oil)
SC/NATS 1840, Biotechnology
28
Cloning Whole Animals
z
In 1997, the sheep
“Dolly” was cloned
from an adult
sheep. Dolly is an
exact replica of its
“mother” – the
animal from which
the cell was taken.
SC/NATS 1840, Biotechnology
29
Stem Cells
z
z
z
z
Most cells in the body of an adult animal are specialized cells,
which have the capacity only to reproduce themselves.
Cells that have the ability to divide and give rise to different kinds
of specialized cells are called stem cells.
At conception, the fertilized egg is a stem cell capable of dividing
and becoming every different kind of cell in the adult body. (They
are “Totipotent.”)
z In humans, the cells that are produced in the first four days or so
after conception are all totipotent stems.
At later embryonic stages and even in the grown adult, there are
stem cells with limited potential to grow into different kinds of
cells. (These are called “Pluripotent.”)
SC/NATS 1840, Biotechnology
30
10
Stem cells, 2
z
The medical potential of stem cells, both the
totipotent and pluripotent is enormous.
z
z
z
If stem cells can be isolated, cultured, and then
grafted into patients, many degenerative diseases
could possibly be reversed.
Cells generated from a patient’s own stem cells,
for example, would not be rejected by the body
the way that the cells of donor organs often are.
Stem cells could be used to regenerate brain and
nerve cells, possibly heart muscle, and many
other possible uses.
SC/NATS 1840, Biotechnology
31
Ethical issues in
Biotechnology
z
There are ethical issues all the way along in
biotechnology because human beings are capable
of manipulating life as never before.
z
z
z
Stem cell research raises the issue of where life begins
and whether cells from a human embryo should be used
for another human’s benefit.
Present stem cell work concentrates on making
regenerative cells for the cure of diseases.
But the possibility of cloning whole human beings has to be
considered.
z Dolly was cloned from a stem cell.
SC/NATS 1840, Biotechnology
32
11