Variations

Have you ever wondered: 'Would I be different if I had grown up in another environment?' Every living thing is the product of the interaction that takes place between genes and the environment.

When you look around, you see differences between individuals. You may notice physical differences or differences in capabilities. For example: you may sing in tune, but your cousin, regardless of how hard he tries, always sings out of tune. Where do these differences come from? The genetic input from your parents is partly responsible, but also your environment plays a role. What are the proportions? Genomics may help us figure this out.


•	Inside the cell
•	Heredity and reproduction

In this section:

Genetic variation: An evolutionary factor

For organisms that produce children through sexual reproduction (where different genes from each parent are combined), an offspring is never an exact copy of its parents. And in almost every case, no two children of the same parents are genetically identical to each other. The exception is identical multiples like twins, who share the same genome.

Thanks to genetic variations received from their parents, certain organisms are better adapted to their environment than others. For example, good camouflage means better chances of escaping from predators, finding food, and having many descendants. This can be seen in these different species.


	Coquina Donax, Donax variabilis, Nova-Scotia.


	Manus Island Tree Snails, Papustyla pulcherrima, New Guinea.


	Noble Scallops, Chlamys senatoria, Philippines.

Non-genetic variations

Certain variations do not have a genetic origin. When plants do not have enough water and food, they will not grow as well as those that do. This variation is not passed on to the next generation. For example, this bonsai tree is a Scotch pine that has been transformed by humans through control of its environment. If its seeds were planted outdoors, its descendants could grow to a height of more than 20 metres.


	Image: Dick Keen, Visuals Unlimited, Inc. Bonsai tree.


	Scotch pine, Pinus sylvestris.

Genes and the environment

Try and guess which is responsible: genes, the environment or both? Select the question mark to find out more.

Mary is a triathlon champion. She always finishes first.		Although researchers have discovered a connection between endurance and a gene called ACE, this gene alone will not make you an athlete. Training, proper nutrition and rest are equally important for success.
Paul often falls asleep in the afternoon. At two in the morning, however, he is wide awake.		Research has shown that the gene 'hPer2' is mutated in patients who suffer from the rare 'Familial Advanced Sleep-Phase Syndrome'. If you have problems getting up in the morning, it might be due to your genes.
Since the age of 25, Zbignew has been bald.		Hair loss is strongly influenced by genes transmitted on the maternal side. So, if Zbignew's daughter had a son, her son would have a 50% chance of going bald.
Phuong is an outstanding musician. She has perfect pitch.		Our genes alone don't make us musicians. Practice and perseverance play an equally important role. The gene for perfect pitch, however, has been discovered.
Philip has always had a preference for other guys.		It's unlikely that there is a single 'gay gene' to determine such a complex thing as sexual orientation. However, our genes may influence the sexual differentiation of the brain and its interaction with the outside world.
Marty bullies other students at school.		Studies done in England and Sweden suggest that this type of behaviour is strongly influenced by our genes. However, the environment plays a great role in permitting or controlling this behaviour.
Oscar can't tell one colour from another.		Oscar is colour blind, and can't distinguish certain colors such as red and green. He inherited a mutated gene from his mother. It is almost always men who are colour blind.
Charlotte has always been the top student in her class.		Although the first gene linked to intelligence was identified in 1997, nothing suggests that intelligence is genetically based. It seems that social and family environments, as well as education, are determining factors.
At 83, Florence still smokes and eats fatty foods.		Researchers have identified over 60 genes linked to aging in rats. A single gene called p21 controls the entire group. Nevertheless, it appears that environmental factors such as nutrition and stress have an equal effect on longevity.
Kim has had asthma since birth.		Asthma, caused by a hyperactive immune system, is linked to several genes. However, the significant increase in asthma cases over the past few years seems to suggest that the environment is also responsible.
Emile loves broccoli, just like her Dad. Her mother, on the other hand, can't stand this vegetable.		Certain people are 'hyper-tasters'. They have more taste buds than others. In general, these hyper-tasters don't like bitter or hot foods... or broccoli.
Tim has tried every diet, but is still overweight.		In certain obese people the gene 'ob' is mutated or absent. This gene produces leptine, a protein that sends the message, "I am full!" to the brain. In other people, however, lifestyles or nutritional habits cause gain weight and obesity.

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Image credits: 1) Anne Botman © Canadian Museum of Nature; 2) Anne Botman © Canadian Museum of Nature; 3) Anne Botman © Canadian Museum of Nature; 4) Dick Keen, Visuals Unlimited, Inc.; 5) © Donna Naughton.