Transcript Selective Breeding - Mrs. Teffeteller's Science Classes

Selective Breeding
Noadswood Science, 2012
Tuesday, July 21, 2015
Selective Breeding
 To understand the importance of selective breeding
Selective Breeding
 What do you understand by the term ‘selective breeding’?
Labradoodle
 Look at the following dogs - crossing a Poodle and a Labrador
results in a ‘Labradoodle’
 What features has the Labradoodle inherited from the Labrador?
 What features has the Labradoodle inherited from the Poodle?
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Poodle
+
Labrador
Labradoodle
Labradoodle
 The Labradoodle is large (like the Labrador), has a fluffy coat
(like the Poodle) which sheds much less than a Labrador’s coat.
They are also generally well tempered and good swimmers (like
both its parents breeds).
 So the Labradoodle has favourable characteristics from both of
its parents breeds
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Poodle
+
Labrador
Labradoodle
Natural Selection
 Species gradually evolve by a process of natural selection
 Individuals in a species show a wide variation (due to gene
differences)
 Individuals with inherited features best suited to their
environment are most likely to survive and reproduce: passing
on their genetic information to their offspring
Natural Selection
 Over time, a species can change its appearance, and may even
become a new species, unable to reproduce successfully with
individuals of the original species
 Individuals with the most favourable genes for the environment
they live in are selected over time: this is natural selection
Selective Breeding
 Selective breeding is a process used to produce different breeds
of animals or varieties of plants that have useful
characteristics
 Using selective breeding you can produce a specific offspring
with useful characteristics of both parents
 What organisms do farmers ‘selectively breed’?
Selective Breeding
 Farmers can choose individual cows to mate in order to produce
a generation of cows that will yield more milk
 Farmers could also selectively breed for docile animals
 Apple growers want to produce a type of apple that is tasty and
resistant to disease. This can be done by crossing a variety of
apple known for taste with another variety that shows strong
resistance to disease
 Farmers could also selectively breed for crops of a uniform
height / when they are ready for harvest
E.g. Cows
 Suppose you wanted a variety of cow that produced a lot of
milk: 




Choose or select the cows in your herd that produce the most milk
Only let these cows reproduce
Select the offspring that produce the most milk
Only let these offspring reproduce
Keep repeating the process of selection and breeding until you
achieve your goal
Animals
 To selectively breed animals often a ‘stud’ male is used to
breed.
 Artificial insemination is also used (where a vet will deliberately
introduce semen into the female)
Summary
 The key is to identify the feature you want, and only breed from
the individuals that have that feature – it is achieved by…
 Select parents with the desired traits (things you want)
 Cross the parents (breed them)
 Select from the offspring
 Repeat (over many generations)…
 Selective breeding is used to:  Choose characteristics of the food item required
 Produce a more uniform crop (size / harvest time)
 Extend the tolerance range of an organism
Perfect Pet
 Imagine you wanted to create your perfect dog – how would you
selectively breed for it?
 What two parents are you going to choose?
 What qualities do each of them have (which you want)
 How are you going to ‘get’ these qualities in your pet?
 Draw out and annotate creating your perfect dog…
Dog Parents
Selective Breeding
This is the oldest type of genetic
manipulation.
Breeding organisms for a desired
characteristic.
Works very well in plants.
Also works with animals, but this can be
more difficult.
Selective Breeding
Mating animals to produce desired traits in
offspring
Racehorses
Dog breeds
Chickens
Variegated roses
Giant pumpkins
Seedless fruits
Inbreeding
• Breeding
organisms with
specific
characteristics
generation after
generation
• This does become
risky because
recessive traits
can surface that
are harmful
Pure Breed Animals
Dogs, Cats, Horses, etc.
End up with many
problems- joint issues,
blindness, etc.
“Mutts” are often more
healthy
Hybridization
• Breeding of two
different species
that results in an
offspring
• Actually happens
in nature
(coydog/dogote
and wolphins)
• Humans can do
this on purpose to
create desired
traits, common
example is the
mule
Hybridization
Liger is another example
Take this just a step further
Scientists can hybridize
the genes by adding
DNA from one organism
to another organisms
egg (meta-cloning)
Example: chickens that
are both meaty and
good egg layers