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Cloning & Genetic
Engineering
D. Crowley, 2007
Cloning & Genetic Engineering
• To understand cloning and genetic
engineering
Cloning
• What is a clone? Is it natural?
• Exact copies of organisms are called clones - they have identical
genetic information as the organism they were cloned from
• Cloning is the production of genetically identical copies
• Clones frequently occur naturally, but they can also be produced
artificially
Natural Cloning
• Plants are easy to clone - gardeners often take cuttings to grow new
plants which are clones
• Cloning is an example of asexual
reproduction (where genetic information
comes from just one parent)
• Potato plants reproduce vegetatively by
growing tubers, from which the new plant will
grow these are clones
Natural Cloning
Other examples include: • A colony of bacteria - each bacterium splits into two, with the total
number doubling every twenty minutes - all genetically identical
• A clump of daffodils - the new plants arising from the original bulb are
exact replicas or clones of the parent (and of each other)
• Strawberry or blackberry runners are clones of the parent plant.
Artificial Plant Cloning
• Clones can also be produced artificially - you can take a small number of
cells from a 'parent' plant and ‘grow’ them in a medium rich in nutrients
and plant growth hormones
Plants Pros & Cons
• Cloning of plants is very important commercially - successful varieties of
plants can be produced on a large scale in a short space of time
• Can you think of any pros / cons of plant cloning?
Advantages of plant cloning
Disadvantages of plant cloning
Plants Pros & Cons
Advantages of plant cloning
Disadvantages of plant cloning
Lots of new plants can be grown in
a short time period
All plants have the same genetic
information - all are vulnerable to
the same disease / pest
Conditions can be precisely
controlled
No new beneficial characteristics
will arise (as they do by chance
naturally)
All new plants get the
characteristics you want - e.g.
disease resistant
No variation causes the gene pool
(no. of genes in a population) to be
reduced
Artificial Animal Cloning
•
Artificial cloning of animals is now commonplace in laboratories: the
most famous example of animal cloning is Dolly the sheep: -
1.
An egg cell was removed from the ovary of an adult
female sheep, and the nucleus removed
2.
The empty egg cell was fused with DNA extracted
from an udder cell of a donor sheep
3.
The fused cell now began to develop normally, using
the donated DNA
4.
Before the dividing cells became specialised the
embryo was implanted into the uterus of a fostermother sheep - the result was Dolly, genetically
identical to the donor sheep.
Animals Pros & Cons
• Animal cloning has potential uses in both farming and medicine (for
protein synthesis (manufacturing proteins), gene therapy (adding /
replacing specific genes to treat diseases) and organ donation (e.g.
kidneys from pigs which can be used in humans))
• Can you think of any pros / cons of animal cloning?
Advantages of animal cloning
Disadvantages of animal cloning
*Interestingly cells seem to ‘know’ their age - so a cloned animal, although just born,
on a cellular basis is as old as its donor parent!
Animals Pros & Cons
Advantages of animal cloning
Disadvantages of animal cloning
Allows you to check the embryo for
defects
No new beneficial characteristics
will arise (as they do by chance
naturally)
Allows you to choose the sex and
time of birth
All animals have the same genetic
information - all equally vulnerable
to the same disease or predator
Exact copies of the ‘best’ animal
can be made year after year
(selective breeding)
No variation causes the gene pool
(no. of genes in a population) to be
reduced
Could be used in saving
endangered species from extinction
Animal welfare concerns - cloned
animals tend to die young*
Genetic Engineering
•
Genetic engineering is very different from cloning
•
How did humans used to change the genetic make-up of organisms we took
advantage of?
– Selective breeding - only breeding the organisms with the characteristics we
wanted
•
Genetic engineering takes genes from one organism, and places them into the
chromosomes of another organism. It alters an organism's genetic code, and
works because there is only one code for life
•
The set of instructions for which a gene is responsible work whichever organism
the gene is in, e.g. a gene for luminescence from a jellyfish can be added to a
frog, making it luminescent too!
Genetic Engineering
• Enzymes are used to cut up and join together parts of the DNA of one
organism, and insert them into the DNA of another organism
• In the resulting new organism the inserted genes will code for one or
more new characteristics - for example producing a new substance, or
performing a new function
• The organism has been
genetically re-engineered
• E.g. a bacterium's genetic
make-up can modified by
splicing a gene into its DNA
Arguments
• Genetic modification can be used to help many people - e.g. people
suffering from diabetes can get their insulin from genetically modified
bacteria, rather than having to extract it from other humans / animals
• Some people believe growing and eating genetically modified plants
could be dangerous because they contain genes which are not natural
Task
• To produce a poster
• listing both the pros
or cons for genetic engineering
(it needs to be informative and catchy to highlight both sides of the
argument for people who do not know much about the subject)
• Whilst doing think where you stand - is genetic modification a good or a
bad thing?