Artificial Selection

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11 Δεκ 2012 (πριν από 4 χρόνια και 6 μήνες)

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A
RTIFICIAL
S
ELECTION





1



Artificial Selection is the process of selecting and breeding individuals
with desirable traits to produce offspring with the desired traits.

The
selection process is simple

-

only those individuals

(animals or plants)
with the desired trait

are allowed to

reproduce.
Some people in
history have tried to do this with humans… can anyone give an example?


The main difference between 'natural' selection and 'artificial'
selection is that, humans control the artificial selection process.


Man has been using art
ificial selection for thousands of years! For
example, archaeological evidence shows us that
:



all of today’s different types of dogs came from one type of
ancestral dog that man tamed about 14000 years ago.



wheat and barley (members of the grass family) w
ere amongst the
first plants grown for food


but although 80 different plants
were domesticated during prehistoric times only a few today make
up the majority of the world’s food supply (e.g. wheat &rice = 40%)


It can take many generations for artificial selection to consistently
produce the desir
ed result. This is because the recessive genes
continue to be present in the mix of some offspring until it is gradually
BRED out… leaving a PUREBRED.


Have you ever herd of a BEEFALO?

It is a cross between a cow and a
bison (or buffalo). It is a CROSS
BREED. Like the bison it has thick
fur to protect it from the cold and the meat is low in fat and
cholesterol.


A
RTIFICIAL
S
ELECTION





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Today man uses a variety of low and high tech methods to try and
speed up artificial selection in animals:



cloning


making life from cells



artificial insemination


artificially joining selected male and
female gametes



in vitro fertilization


make and female gametes are selected and
then allowed to fertilize in a controlled setting before being
implanted into the female



genetic engineering


direct altering of DNA in an organism, then
allowing it to reproduce


In plants man uses selective breeding and genetic engineering to
produce desired results such as
resistance to disease, length of time
to mature, resistance to extreme temperatures (hot

or cold), and even
taste
. Western Red Spring Wheat used for flour to make bread and
Canadian Western Duram used to make pasta are two examples of
grains grown locally. Canola is another good example, selectively bred
to produce lots of high quality oil
(check the margarine or cooking oil in
your house for this)


A
RTIFICIAL
S
ELECTION





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Genetic Engineering

-

moving pieces of DNA from one cell into another,
even from the cell of one animal into the cell of another.


We know that the DNA tells the cell what should look like and
do…
so what happens when scientists change the DNA?

Is this a good thing??


Genetic Engineering allows scientists to move genes from one organism
to another, and characteristics from one species to another. Using
these methods is also called BIOTECHNOLOGI
ES.


Biotechnology has significant implications for modern medicine. One of
the 1
st

uses was to move the human gene for insulin production into
bacteria


thus allowing the bacteria to produce insulin as a waste
product.
Who can s
uggest

why this might be important?

This allows us to produce large quantities of insulin which is important
for diabetics who need regular insulin shots.


Scientists have also c
reated a type of bacteria that can eat oil. It
would be useful to protect our environment when there are big oil
spills.
Do you see any down side (risk) associated with this?


We have discovered how to insert human genes into some animals as
well. This
creates what we call a TRANSGENETIC or genetically
modified animal.
TRANSGENETIC animals are produced by adding
human genes to the fertilized eggs of the animal.

The offspring of a
transgenetic animal will be able to produce the desired human proteins.

For example, transgenetic cows are used to produce “human lactoferrin
(milk with a high source of iron for babies).

Why
might
transgenetics
be important?

Do you think there might be risks?


A
RTIFICIAL
S
ELECTION





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Other examples


sheep are used to produce factor VIII and IX w
hich
are clotting factors used to treat hemophilia and pigs are used to
produce human protein C which is used to treat blood clots in humans.


Transgenetics are also used in our food supply. Who has heard of
Genetically Modified Organisms (GMOs)? An exam
ple is about 15 years
ago the papaya industry in Hawaii was on the verge of collapse due to a
virus that was destroying the fruit. Transgenetics was used


a new
gene was inserted into some plants and over time the population of
papaya plants in Hawaii be
came resistant to the virus.
Can you think of
some pros and cons to this?


Crops such as wheat, corn, tomatoes and potatoes are genetically
modified for various reasons


often to be tolerant to pesticides and
herbicides. T
oday we tend to use fewer species of plants for food
production MONOCULTURES.
What are the benefits of doing this?
How could such practices harm the world’s future food supply?


Biotechnology is also used in
fish farming or AQUACULTURE
. With
declining f
ish stocks (e.g. collapse of Atlantic cod industry),
aquaculture is becoming more and more important as a way of producing
fish for us to eat. Scientists have added genes for disease resistance
to some varieties of fish and also growth hormones are introd
uced to
fish eggs to increase the size and growth rate of the fish.
Researchers are also adding “antifreeze” so some stocks of Atlantic
salmon and halibut… the gene comes from an arctic flatfish.
What
might happen if these “superfish” were to escape from

captivity?