Artifact A
Selective Breeding and Its Effects on Farms
For thousands of years, men have always wanted the best of everything. In the times when most
people were just simple farmers, they still wanted to have the best products of anyone in their
village. To get the most favorable traits in their crops and livestock, they would use the technique of
selective breeding. Selective breeding, or artificial selection, works by allowing only the plants and
animals with desirable traits to reproduce, causing the offspring to take on only the most favorable
traits. In this article, I will go into the details on how humans have impacted the evolution of farm
animals and crops.
The first topic to tackle is how plants have been affected by selective breeding. Farmers attempt to
artificially select plants in order to get a high crop yield, better disease resistance, and faster growth
rate. They may also try and change the cycles of plants in order to produce multiple crops a year.
To get the best possible traits, farmers often employ genetic engineering; they splice a gene with
endonuclease to separate it from the rest of the chromosome, then they implant it into another
organism, giving the recipient of the gene that trait. Plants can continue to be genetically
engineered until all the desired traits are there, then they can be bred with a plant with the same
traits to produce the best possible crops. An example of selective breeding in crops comes from the
wild mustard plant. Wild mustard plants can be bred to cultivate cauliflowers, broccoli, cabbage,
kale, and Brussels sprouts, depending on what traits have been selected. One major problem that
has come from humans’ selective breeding of plants is that we chose to consistently breed annual
crops, which quickly depletes the nutrients in the top layer of soil, forcing farmers to use many
fertilizers and additives to get consistent yields. Hopefully in the future there will be a trait that
farmers can use to help conserve the soil.
Now it is time to shift the topic from plants to animals. Animals are selectively bred on farms to
ensure domestication, to resist diseases, and to get the most produce out of each individual animal.
One trait that farmers artificially selected early on was social behavior: animals that tended to stay
together in a herd or flock were favored for reproduction. This would allow the farmers to raise
many of the same animals in close captivity to each other and keep the animals from attacking one
another. One example of selective breeding in livestock is the artificial selection of cattle. Dairy cows
that produce more milk are more likely to be interbred so their offspring will also produce more milk.
This can keep going for generations, each time improving milk yield. In chickens, only the hens that
lay the most eggs will breed, also increasing output, similar to the dairy cows. A disadvantage that
comes from selective breeding in animals is it becomes nearly impossible to breed out genetic
diseases. Each time a farmer breeds a new generation, they are encouraging whatever genetic
diseases to continue developing in the animal.
There are many advantages and also many disadvantages to artificial selection in farm produce, and
they don’t just affect farms: they will affect everything that is not naturally selected. Selective
breeding decreases the size of the gene pool, losing the variety of life. However, it also allows for
much better production of goods, meaning that more humans will get to eat and survive. Overall,
the good outweighs the bad when it comes to unnatural selection.
http://www5.bluevalleyk12.org/mohn-ap/evan-h/selective-breeding-and-its-effects-on-farms/ April 29, 2014
Artifact B
Heredity and Genes
Heredity is the passing on of characteristics from one generation to the next. It is the reason
why offspring look like their parents. It also explains why cats always give birth to kittens and
never puppies. The process of heredity occurs among all living things including animals, plants,
bacteria, protists and fungi. The study of heredity is called genetics and scientists that study
heredity are called geneticists.
Through heredity, living things inherit traits from their parents. Traits are physical
characteristics. You resemble your parents because you inherited your hair and skin color, nose
shape, height, and other traits from them.
Cells are the basic unit of structure and function of all living things. Tiny biochemical structures
inside each cell called genes carry traits from one generation to the next. Genes are made of
DNA, and different patterns of A, T, G, and C code for the instructions for making things your
body needs to function (like the enzymes to digest food or the pigment that gives your eyes
their color). As your cells duplicate, they pass this genetic information to the new cells.
Genes are strung together to form long chains of DNA in structures known
as chromosomes. Genes are like blueprints for building a house, except that they carry the
plans for building cells, tissues, organs, and bodies. They have the instructions for making the
thousands of chemical building blocks in the body. These building blocks are called proteins.
Proteins are made of smaller units called amino acids. Differences in genes cause the building
of different amino acids and proteins.
Genes are found on chromosomes and determine specific human characteristics, such as height
or hair color. Because you have a pair of each chromosome, you have two copies of every gene
(except for some of the genes on the X and Y chromosomes in boys, because boys have only
one of each).
Most cells in the human body have 23 pairs of chromosomes, making a total of 46. Individual
sperm and egg cells, however, have just 23 unpaired chromosomes. You received half of your
chromosomes from your mother's egg and the other half from your father's sperm cell. A male
child receives an X chromosome from his mother and a Y chromosome from his father; females
get an X chromosome from each parent.
Some characteristics come from a single gene, whereas others come from gene combinations.
Because every person has about 25,000 different genes, there is an almost endless number of
possible combinations!
A gene gives only the potential for the development of a trait. How this potential is achieved
depends partly on the interaction of the gene with other genes. But it also depends partly on
the environment.
http://www.cccoe.net/genetics/heredity.html
Artifact C
Selective Breeding
Selective breeding is the traditional method for improving crops and livestock, such as
increasing disease resistance or milk yield.
Genetic engineering is a faster way, which transplants genes for a desired characteristic into an
organism. However, genetic engineering offers many potential benefits but carries the risk of
unexpected harmful effects.
Selective breeding and genetic engineering
Over the centuries humans have tried to breed better crops and livestock. Traditionally this was
done by carefully choosing parents for breeding that show the required characteristics selective breeding. More recently it's been possible to implant particular genes using genetic
engineering. Both these techniques depend on there being change and variation in the genetic
material – which is caused by mutations.
Mutation
Mutation means any change in the genetic material. Mutation occurs naturally. Most mutations
are harmful to an individual, but occasionally a mutation can be beneficial. It's possible to speed
up mutation rates artificially using radiation or chemicals. Mutations bring about changes in
organisms by changing the sequence of bases in DNA. This causes a different protein to be
made, or blocks the production of the protein completely.
Selective breeding
These are the steps in selective breeding:
1. Decide which characteristics are important
2. Choose parents that show these characteristics
3. Select the best offspring from parents to breed the next generation
4. Repeat the process continuously
Examples of selective breeding
Wheat - Producing disease-resistant wheat by crossbreeding wheat plants with disease
resistance and wheat plants with a high yield.
Dairy cattle - Increasing milk yield by selecting bulls from high yield herds and breeding them
with cows that have the best milk production.
Cattle breeds - Selective breeding can also be used to modify other characteristics of
cattle.
Problems with selective breeding - higher tier
Future generations of selectively bred organisms will all share very similar genes. This could
make some diseases more dangerous as all the organisms would be affected. Also there's
increased risk of genetic disease caused by recessive genes.
Some genes would be lost, making it more difficult to produce new varieties in the future. In
scientific language this would be described as ‘inbreeding can lead to a reduction in the size of
the gene pool’.
Genetic engineering
A faster way of producing new varieties is to transfer the genes for the desired characteristic
into an organism artificially. This is genetic engineering. The gene may have come from the
same species, but genetic engineering also allows the genes from an unrelated organism to be
transferred – something that's not possible with selective breeding.
Genetic engineering can be used to create new varieties of plant and animal, but there's
a risk that there could be unexpected harmful effects, either to the new organism or if the gene
“escapes” into the surrounding populations. Some people are concerned about the health risk of
eating genetically modified food – others think it wrong to create new life forms, or move
genes between different species, especially if this causes harm to the receiver.
http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/living/genesrev1.sh
tml
Artifact D
Biotechnology
James Watson and the late Francis Crick with a DNA helix model James Watson and the late Francis
Crick discovered the structure of DNA in 1953; Watson has spoken in favor of genetic engineering.
Biotechnology isn't something new - selective breeding to create more useful varieties of animals
and plants is a form of biotechnology that human beings have used for thousands of years.
Biotechnology may include any use of science or technology to alter the characteristics of a
particular breed or animal.
Biotechnology can be good or bad for animals - and it may also produce an answer to the ethical
problems of experimenting on animals.
Human problems
Newspaper articles about the ethical problems of genetically engineered animals are usually
concerned about the danger these animals may pose to human beings (usually to human health),
rather than any implications for the animals themselves.
Animal rights
Genetic engineering and selective breeding appear to violate animal rights, because they involve
manipulating animals for human ends as if the animals were nothing more than human property,
rather than treating the animals as being of value in themselves.
Recent action to allow animals to be patented reinforces the idea of animals as human property,
rather than beings in their own right.
Animal welfare
Biotechnology can be good for animals. Selective breeding and genetic engineering can benefit
animals in many ways:
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Improving resistance to disease
Breeding to remove characteristics that cause injury – Ex. selecting cattle without horns
But biotechnology can also be bad for animals - the good effects for the breeder can offset by
painful side-effects for the animals:
Modern pigs have been bred to grow extra fast - some breeds now grow too fast for their hearts,
causing discomfort when animals are too active
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Broiler chickens are bred to grow fast - some now grow too fast for their legs
Regulating genetic engineering
Profitability is one of the major drivers of both selective breeding and genetic engineering.
If animal welfare is not to be compromised, research must be restricted by a counter-balancing
ethical principle that prevents altering animals in a way that was bad for the animal.
http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/living/genesrev3.shtml
Artifact E
Artifact F
Artifact F
Essay Questions: How do genes influence traits? What is selective breeding and how is it
beneficial? Would you argue in favor of or against genetically designing babies and
genetically enhancing human beings?
Original concept found on TPT and produced by JCB Education Services 2013. Modified 3/2015