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Genetically Modified Foods
http://kidseatgreat.com/genetically-engineered-food.htm
http://www.webmd.com/a-to-z-guides/features/are-biotech-foods-safe-to-eat
The term genetically modified food (also known as biotech or genetically engineered food) refers
to crop plants that have been modified in the laboratory to enhance desired traits, such as
resistance to herbicides or improved nutritional content. With genetic engineering (GE), any
gene from a plant, animal, bacterium, fungus, or virus can be inserted into the DNA of another
organism.
Experts say 60% to 70% of processed foods on U.S. grocery shelves have genetically modified
ingredients. The most common genetically modified foods are soybeans, maize, cotton, and some
oils. That means many foods made in the U.S. containing field corn or high-fructose corn syrup,
such as many breakfast cereals, snack foods, and the last soda you drank; foods made with
soybeans and foods made with cottonseed and canola oils could likely have genetically modified
ingredients.
Benefits include:
 Increased pest and disease resistance
 Drought tolerance
 Increased food supply
Risks include:
 Introducing allergens and toxins to food
 Accidental crosses between genetically modified and non-genetically modified foods
 Antibiotic resistance
 Negatively changing the nutrient content of a crop
 Creation of "super" weeds and other environmental risks
Are Genetically Modified Foods Safe?
Many scientists agree that overall, the current genetically modified crops -- which are generally
one-gene additions -- are safe. No food is 100% safe -- genetically modified or not -- and the
odds of having a negative reaction to a genetically modified food are very small.
However, one of the major issues consumers face is that GE products are not labeled as such in
the United States. Many other countries, such as Europe, Japan, South Korea, Thailand, and
New Zealand, have GE regulations and labeling requirements.
E. Gratkins, Smith JH
Page 1 of 9, rev. 6/19/2017
Selective Breeding
http://www.s-cool.co.uk/gcse/biology/genetic-crosses/selective-breeding-crosses.html
Knowing about genes allows you to decide which plants or animals to breed together to produce
offspring with desired traits. This process of choosing which parent plants or animals to use is
called selective breeding.
Selective breeding is straight forward enough.
1. Choose your best animals (or plants) and breed them together.
2. Then choose the best of their offspring (F1 generation). Breed these ones again to give
an F2 generation.
3. Carry this on over many generations until you have the 'perfect' animal (or plant) – or at
least the one with the characteristics or traits that you wanted.
Why selective breeding is useful
You can easily imagine that one big reason for selective breeding is money. You can save a lot
of wasted money if you weed out weaker individuals. For example, you could selectively breed a
plant for disease resistance. You can also ensure that you get the maximum harvest and
therefore are more efficient. More corn grown on each plant means more money.
Problems with selective breeding
There's an old expression about putting your eggs in one basket. If you selectively breed for
certain characteristics you are really selecting certain alleles. Over a few generations you lose
the non-selected alleles from the population. This means you reduce the variety of alleles that
individuals have and that are available for passing on.
What happens if it turns out that those lost alleles had an advantage? Perhaps they give
resistance to a new disease? Without the allele all your best crops or animals could die?
Many domestic dogs are pedigree (purebred) dogs such as Dalmatians and Golden Retrievers,
etc. Over many generations their characteristics have been chosen. However many breeds of dog
show specific weaknesses and bad health problems because of the limited number of alleles
available. Mutts tend to have less health problems because they have a good range of alleles to
choose from.
E. Gratkins, Smith JH
Page 2 of 9, rev. 6/19/2017
Cloning Pets
http://www.worldalmanacforkids.com/
A clone is an organism that is an exact genetic copy of another organism. Scientists have been
able to clone mammals artificially. The most famous clone was a sheep named Dolly, born in
Scotland in 1996. Seven years later, after developing arthritis and a lung disease, Dolly died. She
was young by sheep standards, and scientists were not sure whether her bad health came from
being a clone.
In a traditional cloning, scientists take a fully grown egg from an animal's ovary (where the
female animal produces eggs). They take out the egg’s genetic material, and replace it with the
genetic material from the animal that they are trying to clone. The two cells are shocked. The egg
then starts to divide and form an early embryo (an animal that is just beginning to develop). After
a few days, the scientists put the embryo into a surrogate (substitute) mother’s uterus (womb)
where it continues to develop before being born.
In February 2002, researchers in Texas announced the birth of "CC" (carbon copy), the world's
first cloned cat. CC has the same DNA as Rainbow, the cat she was cloned from. But they look
different, because calico patterns are affected by growth in the womb, not just genes. They differ
in other ways too, such as personality and weight.
Researchers are also trying to clone extinct animals -- such as the Tasmanian tiger and
mammoths -- using DNA from specimens kept in museums or found frozen in glaciers. Most
scientists say that cloning dinosaurs -- as in the movie Jurassic Park -- is probably impossible,
however, because they won't be able to find remains with enough intact dinosaur DNA.
Whether you think cloning is cool or creepy, remember that a clone is never an exact copy of an
animal. The environment also affects your DNA. Identical twins are like clones because they
have the same DNA, but they are two unique people - each with their own thoughts and
experiences.
E. Gratkins, Smith JH
Page 3 of 9, rev. 6/19/2017
Twins
http://kidshealth.org/
http://www.seattlechildrens.org/
In 2002, there were 125,134 twin babies born in the United States. There are two kinds of twins:
fraternal and identical. The difference comes from the way the egg is fertilized when a woman
becomes pregnant.
In fraternal twins, two different eggs are fertilized. Fraternal twins often don't look alike and
only share approximately half of the same genes - just like non-twin brothers and sisters who are
born to the same parents. They can even be different sexes.
With identical twins, one fertilized egg splits into two. That's why identical twins usually look
almost exactly alike and share the same genes. If you have friends who are twins and you have
trouble telling them apart, they are probably identical.
Twins whose bodies are connected are called conjoined twins. Conjoined twins begin as a
single fertilized egg. The exact cause of conjoined twins is not known. There are two theories.
One is that the egg divides late and does not divide completely. The other is that the egg divides
completely but then fuses (joins) back together.
The connection between the twins’ bodies may be fairly simple. They may share only a small
amount of tissue, and each child may have all the organs and other structures they need. For
example, the twins may be joined at the belly with a “bridge” that connects their livers.
Usually the connection is more complex, and sometimes it is very complex. The children may
share:
 Vital organs, like one heart
 Many structures, like several parts of their digestive, circulatory, and urinary systems
 A large segment of their body, like all of their lower body
 Part of the brain and skull
Sometimes, with very complicated, delicate surgery, the twins can be separated. Sometimes,
they cannot.
E. Gratkins, Smith JH
Page 4 of 9, rev. 6/19/2017
Genetic Disorders
http://kidshealth.org/
Gene mutations
Cells can sometimes contain changes or variations in the information in their genes. This is
called gene mutation. As cells are aging or have been exposed to certain chemicals or radiation,
it is normal to have some gene mutations. Most of the time, cells recognize these changes and
repair them. Other times they can cause illnesses. If a gene mutation exists in egg or sperm cells,
children can inherit the gene mutation from their parents and may have a genetic disorder.
Dominant gene disorders
If a person carries the dominant gene for a disorder, he or she will usually have the disorder, and
also has a 50% chance of passing on the disorder to a child. Disorders caused by a dominant
gene include achondroplasia (a form of dwarfism) and Marfan syndrome (a connective tissue
disorder—connective tissue holds the body together and provides a framework for growth).
Recessive gene disorders
People who have one recessive gene for a disorder are called carriers. Carriers don't usually
have the disorder since they have a normal gene in the gene pair to do the job. If two carriers
have a child together, the child has a 25% chance of getting the abnormal gene from both parents
resulting in the disorder. Cystic fibrosis (a lung disorder) and sickle cell anemia (a blood
disorder) are caused by abnormal recessive genes from both parents coming together in a child.
X chromosome disorders
Some recessive disorder genes are carried only on the X chromosome. Since guys only have one
X chromosome, there is no normal (dominant) working gene so the disorder shows up. Since
girls have two X chromosomes, so they would need to inherit two copies of the abnormal gene to
get the disorder. X-linked disorders include hemophilia (a bleeding disorder) and color
blindness.
Too many or too few chromosomes
Sometimes when an egg and sperm unite, the new cell gets too many or too few chromosomes.
Most children born with Down syndrome, which is associated with mental retardation, have an
extra chromosome number 21.
E. Gratkins, Smith JH
Page 5 of 9, rev. 6/19/2017
Gene Therapy
http://kidshealth.org/
In some cases, people who are concerned that they might carry certain gene mutations can have
genetic testing done so they can learn their children's risk of having a disorder.
Gene therapy is a promising new field of medical research. In gene therapy, researchers try to
deliver copies of healthy genes to cells with damaged or missing genes so that the "good" genes
will take over. Viruses are often used to carry the healthy genes into the targeted cells because
many viruses can insert their own DNA into targeted cells.
Gene therapy is a technique for correcting defective genes responsible for disorders. Researchers
are experimenting with several ways of correcting defective genes:
 A normal gene may take the place of a damaged or defective gene
 An damaged or defective gene could be repaired
 A damaged or defective gene could be turned off or a normal gene turned on
Gene therapy does have risks and limitations. Scientists haven't yet identified what every gene
in the human body does. For most disorders, scientists don't know if and how genes play a role.
Plus, there are major difficulties putting the normal genes into the proper cells without causing
problems for the rest of the body. The viruses and other agents used to deliver the "good" genes
can affect more than the cells for which they're intended. If a gene is added to DNA, it could be
put in the wrong place, which could potentially cause cancer or other damage.
There are also concerns that people might try changing genes for morally troubling reasons, such
as to make smarter or more athletic children (known as “designer babies”). No one knows what
the long-term effects of that kind of change would be. Still, for many people who have genetic
disorders, gene therapy holds the hope that they — or their children — will be able to live better,
healthier lives.
E. Gratkins, Smith JH
Page 6 of 9, rev. 6/19/2017
Radiation Therapy
http://kidshealth.org/
Radiation therapy is one form of treatment for people who have cancer. Both adults and kids can
get cancer, but kids don't get it very often. Cancer is a disease that causes normal cells in the
body to grow out of control. If left untreated, these cells can grow throughout the body, making
the person very sick. Radiation therapy kills cancer cells and keeps them from growing and
multiplying.
How Is Radiation Given?
Cancer can be treated with radiation therapy alone or in combination with chemotherapy or
surgery. Chemotherapy is a treatment that uses medicine to destroy cancer cells. Some people
may first have surgery to remove cancer cells or tumors and then have radiation therapy.
Radiation therapy can be given in two ways. A person may receive radiation directed to the
outside of the body called external radiation. Or a person may receive radiation therapy that
places the radiation inside the body, which is called internal radiation therapy (putting
radioactive material directly in the tumor). Some people may receive both types of radiation
therapy.
What Happens During Radiation Therapy?
At each appointment, a large machine is positioned to deliver the exact amount of radiation
necessary to kill the cancer cells. It usually takes only a few minutes for a person to receive the
daily dose of radiation.
During a radiation treatment, a person has to lie still. People who are having external radiation
therapy usually visit the hospital on weekdays for several weeks. These doses of radiation are
small, but they are strong enough to kill cancer cells. The radiation also can damage normal
cells. Weekend breaks from radiation treatments give normal cells a chance to recover and let
new, healthy cells grow.
E. Gratkins, Smith JH
Page 7 of 9, rev. 6/19/2017
DNA Profiling
http://www.worldalmanacforkids.com
Every cell in every living thing (or organism) has DNA, a molecule that contains all the
information about that organism. Building on research by others before them, the structure of
DNA was discovered in 1953 by the British scientist Francis Crick and the American scientist
James Watson.
Sections of connected DNA molecules, called genes, are like tiny pieces of a secret code. They
determine what each organism is like in great detail. Almost all the DNA and genes come
packaged in rod-like structures called chromosomes-- humans have 46. There are 22 almost
identical pairs, plus the X and Y chromosomes, which determine if a human is male (one X
chromosome and one Y chromosome) or female (two X chromosomes).
Genes are passed on from parents to children, and no two organisms (except clones and identical
twins) have the same DNA. Many things—including the color of our eyes or hair and whether
we're tall or short—depend on the genes we get from our parents.
DNA is located in each of your cells, including your blood, saliva, hair follicles, and skin. No
one else has a DNA pattern exactly like yours. For these reasons, DNA evidence can be collected
from skin or hair collected a crime scene and then be linked to a suspect. Forensic scientists can
analyze the exact makeup of the two sets of DNA, and if they are identical, chances are that they
are from the same person. This is called DNA profiling.
DNA evidence is also helping show that some wrongly accused and convicted people are
innocent. Since 1992, DNA evidence has helped reverse at least 78 convictions (including 10
cases where the death penalty was involved). In January 2001, a man imprisoned for murder in
Texas was released because of DNA tests. Another man, sentenced to death for a murder in
Virginia in 1982, was set free in February. New evidence based on DNA tests cleared him of the
crime.
E. Gratkins, Smith JH
Page 8 of 9, rev. 6/19/2017
Human Genome Project
http://www.worldalmanacforkids.com
http://www.ornl.gov/sci/techresources/Human_Genome/project/info.shtml
The Human Genome Project (HGP) was begun in 1990 as an international research program
formed to locate and identify all of the genes of human beings. All our genes together are known
as our "genome." The human genome has also been called the genetic code for our species. In
early 2003, researchers succeeded in mapping out the locations of the genes on all 23 pairs of
human chromosomes.
Our chromosomes, and therefore our genes, are made up of the chemical DNA
(deoxyribonucleic acid). The structure of DNA resembles a twisted ladder. The 'rungs' of the
ladder are made of paired molecules called bases. There are four different bases in DNA:
adenine, guanine, cystine and thymine. The order of these four bases forms the language that
tells the cell what to do. A complete strand of DNA can be millions of base pairs long.
A genome is an organism’s complete set of DNA. Genomes vary widely in size: the smallest
known genome for a free-living organism (bacteria) contains about 600,000 DNA base pairs,
while human and mouse genomes have some 3 billion. Except for mature red blood cells, all
human cells contain a complete genome.
DNA in the human genome is arranged into 46 distinct chromosomes--physically separate
molecules that range in length from about 50 million to 250 million base pairs. Each
chromosome contains many, many genes, made up of long sections of DNA. The human genome
is estimated to contain 20,000-25,000 genes.
Now that the human genome is mapped, scientists are working hard to try to understand how all
of the genes work. By studying human genes, scientists can learn more about hereditary
disorders and get a better idea of how humans have changed over time.
E. Gratkins, Smith JH
Page 9 of 9, rev. 6/19/2017