Transcript 2015 selective breeding powerpoint

Genetic
Manipulation
Selective Breeding
Artificial Insemination
Vegetative Propagation
Genetic engineering and transgenics
How can we manipulate species?
Genetic manipulation
An outline of the principles is required, with advantages,
disadvantages and limitations.
Selective breeding, outbreeding and crossbreeding
• Outbreeding involves breeding between individuals
that are not closely related.
• To delete undesirable characteristics.
eg to prevent recessive inherited diseases, such as
deformed spines and poor lung development in cattle.
• To enhance desirable characteristics
eg yield, growth rate, nutritional value.
• To combine different desirable characteristics
eg Zebu cattle (heat tolerance) × Ayrshire cattle (high
milk yield).
Manipulation of the food species.
Genetic Manipulation by Breeding
Use the text book or the internet to find out the following;
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What
What
What
What
is
is
is
is
selective breeding?
cross breeding?
inbreeding?
hybrid vigour and heterosis?
What is the difference between asexual
reproduction and sexual reproduction?
What are the desirable characteristics of these
species?
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Selective Breeding
Selective breeding involves:
• Identifying the characteristics or “traits” that you want e.g. low fat
content in cow milk or fast growth rate in rice
• Selecting the 2 unrelated individuals you are going to use
• Mating these 2 together (out-breeding)
• Selecting the offspring that show the desired characteristics
Mate With
X
Cow 1:
High milk yield
Low fat milk
Bull 1:
High beef yield
Docile
Calves with high yield of low fat milk,
good meat production & docile
Aims of Selective Breeding
Crop/animal
Bulls
Rice
Desired characteristics
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Wheat,
Potatoes
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Tomatoes
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Cows
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Aims of Selective Breeding
Crop/animal
Bulls
Rice
Desired characteristics
• High meat: fat ratio
• High food conversion ratio/Gross
Growth efficiency
• Good response to fertilisers
• Stem strength
• Resistance pest and drought
Wheat,
Potatoes
• Drought, pest & frost tolerance
Tomatoes
• Uniformity of appearance
• Resistance to viral attack
• Improved taste
Cows
• High milk production
• Low fat content of milk
Rice Breeding
The International Rice Research
Institute in the Phillipines has
been breeding rice since 1959
• They collected hundreds of different varieties & selected those with
desirable characteristics
• They cross-bred useful varieties by taking pollen from one variety
and brushing it onto the stigmas of another variety
• The seed that formed was sown and the resulting plants assessed.
Promising plants were then
cross – bred again etc etc
Rice Breeding
Miracle Rice (IR8)
Dwarf variety from China
x
Tall variety from Indonesia
4 generations of breeding
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Dwarf
Strong stem
Fast maturing
High yield
IR8
Problems:
• Susceptible to disease
• Became hard after cooking
Breeding with 13 more varieties
More crosses
IR36
IR72
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Semi-dwarf
High yield
Fast maturing
Disease resistant
Selective Breeding of Cattle
• Breeding closely related individuals results
in in-breeding
• This increases the chances of harmful,
recessive genes being expressed
• To avoid this, farmers keep careful records
of all crosses and individuals from very
different genetic lines are periodically
crossed = outbreeding
• Outbreeding results in hybrid vigour
What are the advantages of selective
breeding?
Selective breeding has produced varieties that have:
Improved food conversion ratios
eg faster crop growth rates, increased Gross Growth Efficiency of
livestock
eg short stemmed cereals convert more energy into harvestable
crop
Desirable qualities
eg better taste, improved nutritional content
Pest and disease resistance
eg potatoes that are resistant to fungal disease
Uniformity of appearance
eg fruit of the same size and shape to suit retail needs
Timing of growth stages
eg cereal crops that are all ready for harvest at the same time
Dependence on husbandry by humans
eg highly productive crops that rely on high fertilizer and water
inputs. Genetic crop uniformity may require the purchase of F1
hybrid seeds every year.
This ppt can be found at Z:\Geography\Env STUDIES\ENVS4\2014 Selective Breeding.ppt
Research taskManipulation of the food species.
Selective Breeding, Methods of Reproduction.
• Vegetative propagation (including micropropagation)
• Artificial Insemination
• Embryo transfer.
For your selected method of reproduction research the following;
1. An explanation of the science behind the technique
2. An example of a species on which this techniques is used.
3. Advantages and disadvantages of the technique
Set your work out under the headings.
Add pictures and web references.
Save your work to X:\Geography\Environmental Studies\Agriculture
Artificial Insemination
Sperm is obtained from, for example, a desirable bull
and frozen
It can then be injected into females without the need for
mating
• This allows hundreds of cows to be fertilised so that
desirable characteristics can be developed in many
herds
• The desirable traits of a bull can be maintained long
after the actual bull has died and so farmers do not
need to keep the bulls
• Farmers can insure fertilisation of many cows is
synchronised, allowing easier management of the herd
• However, if many cows are inseminated using sperm
from a small number of bulls, there is a risk of reduced
genetic diversity (remember the elms!)
Embryo Transfer
Cow with desired characteristics (e.g. high
milk production or high protein/low fat
content of milk) is treated with folliclestimulating hormone (FSH). This hormone
causes the cow to produce more eggs.
Advantages
• The sex of the introduced sperm can be chosen. So if a farmer wants
males for beef cattle he will choose Y sperm. If he wants cows for
milk he will choose X sperm
• With sheep, this technique can be used to produce
multiple offspring, rapidly increasing flock size
• Using FSH allows control of the oestrus cycle of the
herd, thus when and how many pregnancies occur
Embryo Transfer
There are two techniques available for embryo transplantation:
Technique 1:
Sperm from a desired bull is introduced into the cow by
artificial insemination
The sperm fertilise some of the eggs and embryos
develop
Embryos are removed from the cow after 6-8 days
before they attach to the uterus wall
Embryos can be frozen in liquid nitrogen and used later,
or directly transferred into the uterus of the recipient
cow
Embryo Transfer
There are two techniques available for embryo transplantation:
Technique 2:
Eggs are removed from the ovaries of dead cows and
cultured in a laboratory
The eggs are fertilised using desirable sperm and the
embryos are grown
The embryos are then transferred to the recipient
cows
Vegetative Propagation
Some plants reproduce by turning their stems or roots into new
plants
Example 1: Strawberry plant
Mother plant produces
runners from buds near the
ground
Daughter plant eventually
grows its own roots
Runner dies: we now have
two separate strawberry
plants
Vegetative Propagation
Some plants reproduce by turning their stems or roots into new
plants
Example 2: Potato plant
aerial shoot
daughter bulb
stolon
adventitious root system
old potato (tuber)
Nodes in the buried stem produce stolons. The stolons grow horizontally
through the soil and tubers form at their tips. Each tuber is capable of
growing into a new potato plant
Vegetative Propagation
Advantages
Vegetative organs are bigger than seeds – so the new plant gets lots of
food and can out-compete other plants
Disadvantages
• Most types only produce small numbers of new plants
• Being genetically identical the entire population may be wiped out by
a disease
Genetic Engineering and Transgenics
A transgenic organism or genetically modified organism is one that
has had a gene from another organism inserted into it
Aims of genetic engineering:
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Increase growth and yield
Reduce the need for chemical pesticides and herbicides
Reduce water use
Develop plants that are productive in marginal farmland
Increase nutritional quality
Improve flavour and appearance
Improve plant qualities for harvesting, shipping and storage
The genetic code is universal – a gene that codes for a useful
protein in a bacterium will, if it is cut out and inserted into a cow,
produce the exact same protein in the cow
Genetic Engineering and Transgenics
Maize and the corn borer
Maize is attacked by corn borer insects
A gene from a bacterium ( Bacillus
thuringiensis ) has been chopped out of
the bacterium and inserted into maize
The gene codes for production of a
protein called BT toxin which kills any
corn borer that feeds on the maize
Q What are the benefits of Bt maize?
• Higher crop yields
• Reduced use of insecticidal sprays
• Reduced cropland, more for conservation?
Q What are the possible problems?
• Humans or other animals that eat the maize may be harmed by the BT toxin
or the bacterial DNA
• Non-target insects may be killed, disrupting food chains and pollination
• Spread of the gene into wild plant species with unknown consequences
Transgenic Livestock
A useful gene can be inserted into a zygote nucleus, sperm cells or
into body cells using special viruses
By inserting useful genes into
livestock we may be able to
improve characteristics such as:
• Growth rate and body
composition e.g. pigs
• Disease resistance
• Reduced lactose content of
milk
Producing transgenic animals
is problematic because:
• Most characteristics are
controlled by several genes,
not just one
• Transferring genes so that
they are expressed is
extremely difficult and
expensive
Pronuclear
injection or
nuclear transfer
Transgenic
founder
animals
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Increased milk production
Increased feed and usage growth
Improved carcass composition
Increased disease resistance
Enhanced prolificacy and/or reproduction
Combining GM with Crossbreeding
Read the passage and answer the questions
Consumers do not like GM. Now Monsanto and DuPont are turning to markerassisted selection (MAS). This involves analyzing plants for genetic markers
associated with desirable traits, then using conventional breeding methods to
introduce the genes into a host. The markers are used to quickly identify the
superior seedlings.
For example, a wild apple variety might have a brilliant red skin. Scientists scan
the apple's genome for the gene responsible. They then search the chromosome
containing the skin colour gene for a unique and easy-to-identify segment - the
marker. After crossbreeding the wild apple with a domestic variety, scientists
look for the genetic marker rather than waiting a few years to see which of the
seedlings picked up the red skin trait.
This is much faster than growing the seedlings to see which trees have the redskinned apples.
Questions for discussion
1. Suggest why consumers “ do not like GM”
2. What problems does this technique overcome?
3. Is this an example of transgenics?
Task
Working in groups, prepare short
reports on the folowing issues:
• Bt crops and Monarch butterflies – is
there a problem?
• Isn’t genetic engineering just faster
selective breeding?
• Is there any evidence that genes inserted
into crops can spread to and harm wild
plants?
• Does the use of GM crops really reduce
pesticide use?