The Field of Genes
Breeding plants and animals to produce more, larger, or better foods or animals is the oldest form
of applied genetics. For centuries, farmers have been selecting animals and plants to grow based
on specific traits, for example, horses that are large and strong and corn that grows fast and has
large ears. This way of controlling what you get is called selective breeding. Mendel's
experiments showed us how this can be done.
Today there are several other methods used to get the organisms we want, other than the practice
of selective breeding; these include inbreeding, hybridization, and cloning.
1. Inbreeding involves crosses between closely related individuals of the same species.
This can be done by crossing brother and sister plants or animals. With plants, this
happens by self-pollination (remember Mendel's work?). The advantage of inbreeding is
that a common set of chromosomes is passed on.
Look at each of these dogs. Can you guess what traits each has been inbred for?
Greyhound
Huskie
Doberman
There are some problems with inbreeding. Sometimes a trait that was not expected or wanted is
passed along to the offspring; this can lead to illness or death. Many inbred animals have health
problems such as weak hips.
2. Hybridization involves crossing two related breeds of the same species to produce
offspring with specific characteristics. Often the hybrid is stronger and larger than either
parent.
There are some problems with hybridization. The resulting offspring of hybridization crosses are
often sterile (unable to reproduce). This means this process can be very costly to keep up.
Did you know?
The offspring of a male horse and a female donkey is called a hinny.
A donkey has 62 chromosomes, whereas a horse has 64. Hinnies,
being hybrids of those two species, have 63 chromosomes and are
sterile. The uneven number of chromosomes results in an incomplete
reproductive system.
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3. Cloning involves the removal of a single cell from an organism and then culturing it
under specific conditions into a new organism. If the cell used is a somatic or body cell,
the new individual will be an exact copy of the original. It is sort of like a photocopy
machine; put the original copy on the glass, push a few buttons, and out comes multiple
copies of the original. Simple, right?
It may sound easy but it's not. There are a lot of steps involved and it takes a lot of time and
money to perform. Note that this type of cloning is really a form of asexual reproduction.
Enter Genetic Engineering …
Genetic engineering enables scientists to create plants, animals, and microorganisms by
manipulating genes in a way that does not occur naturally. Manipulated? How? Specifically, this
means that the genes of one organism have been "cut out" and then "pasted" into another
organism. So, how often does this happen, you may ask? Well more often than you think!
Genetically modified (GM) foods, more accurately called genetically engineered foods, are
foods that we eat every day. Some estimate that as many as 30 000 items
found on grocery store shelves contain ingredients that have been
“modified”.
The typical Canadian kitchen is likely to contain many ingredients or foods
that have been genetically modified. Everything from bread, tomatoes,
corn, and soya oil has been produced from altered food organisms.
So, which foods are more likely to have been genetically
engineered? More than 80% of canola grown in Canada and a
high proportion of the country's soybean and corn crops are
genetically modified.
GM plants are often created to
resist disease and eliminate the need for pesticides. Other desired
characteristics, such as a hardier texture, higher nutritional
value, or faster growth, are chosen to produce a kind of "super
food."
Should You Be Worried About Eating Your Dinner Tonight?
About 60% of our processed foods contain some genetic modifications, but consumers in Canada
would be hard pressed to find out what is and isn't altered.
Complete the “What’s in Your Food?” discussion and opinion paper assignment.
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