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Basic Genetic Concepts And Facts

What is a gene?

A gene is stretch of DNA that codes for specific protein. The sequences of bases - C, T, A, G - along this stretch of DNA determines the linear sequence of amino acids in the protein. And the protein's amino acid sequence, in turn, determines what the protein is and what it can do.

Are animal genes different from human genes?

Animal genes and human genes work in precisely the same way. Of course, all differences between a human and a dog ultimately go back to differences in their genes and the proteins for which tose genes code. Genetically, however, those differences are surprisingly small.

Is each trait of an animal - coat or eye color, for example - controlled by a specific gene?

Not necessarily. Many of the traits of greatest interest, such as body size or intelligence, controlled by a number of different genes. These traits are said to exhibit "polygenic inheritance." And even when a trait is primarily controlled by a single gene, other genes may modify its expression; thus, for example, a Siamese cat's "black coat" gene is overridden by a gene that knocks out all coat color except in the ears, paws, and tail.

Polygenic inheritance may be of two types. One is blending inheritance, exemplified by body size, in which each gene contributes to the overall effect and the phenotype varies smoothly from one extreme to the other. The other is a threshold effect, exemplified by hip dysplasia in dogs. In this case, the effect appears when the number of genes contributing to it exceeds a certain threshold. Animals with a number of contributing genes below will be phenotypically normal.

Polygenic inheritance makes it difficult to identify the individual genes involved, which is part of the reason the concept is so often skipped over in elementary genetics discussions.

Does an animal's genetic make-up uniquely determine what it will be?

No. An animal's genetic make-up (its genotype) determines its potential. How much of that potential, good or bad, is actually achieved (the animal's ultimate body form and function, or phenotype) depends on the environment to which it is exposed. This environment includes the animal's nutrition.

This effect is not simply a matter of phenotype = genotype + environment, as it is so often expressed, because genotype and environment interact: The environment that will permit optimum expression of one set of genes may actually prevent another from achieving its full potential - a goal that remains distant today - can we select the environment that will allow optimum development and produce the healthiest, happiest animal possible.

Why is it helpful for scientists mapping the canine genome to have a common set of reference DNA samples?

Mapping the genome essentially consists of placing "road signs" at various points along the chromosome. New road signs are placed by reference to those already known. Thus, if two research groups are working with DNA samples that do not have at least some identified road signs in common, neither can relate its road signs to those placed by the other team. Rather than working together to create a common map, the two teams will end up creating separate, mutually unintelligible maps.

If the two groups can work with the same reference DNA to identify one or more markers in common, then each will be able to place its road signs relative to that marker. As a result, they will be able to merge their maps into a single, more complete map.

How does mapping and sequencing the canine genome help us understand how to improve the health of our dogs?

When a genome does wrong, we can see the results in the animal's body. But looking at the results does not tell us what went wrong at a molecular level. That requires tying phenotype back to the particular gene or genes involved, and identifying how those genes affect the biochemistry and structure of the animal's body. Know that, we can begin to plan treatment strategies that might otherwise be impossible to contemplate. For example, perhaps adding some simple molecule to the animal's food - or removing one usually present - may correct the problem. Or we may be able to work at a more fundamental level, by turning up the activity of a compensatory gene or even altering the animal's DNA to restore the defective gene to normal.

Furthermore, knowing what genes cause what problems, and how, will help breeders eliminate those genes from the stock and ensure that all animals are born with the potential for a healthy, happy future.

What is a canine reference family? Why are canine reference families important?

A canine reference family is a dog family in which individual members differ genetically in simple, obvious ways and in which blood samples (as a source of DNA) can be obtained from grandparents, parents, and siblings. The blood samples or the resulting DNA are then stored and distributed together.

By correlating the genetic differences in the individual animals with their known pedigree and with corresponding differences in their DNA, researchers can place the corresponding road signs on the chromosome. Different research groups can then place their road signs relative to these common reference markers, allowing separate maps to be combined.

How does genetic research help us as ordinary pet owners?

As we learn more about the genetics of our companion animals, we will be better able to care for them. If they need a special diet to achieve their fullest potential, for example, we will be able to provide that diet. We will also be able to see that they get an appropriate amount of exercise and otherwise encounter the environment that is optimal for their particular genetic background.

But there is more. Today, people often choose a particular breed because its disposition and other characteristics fit their needs and lifestyle. But not all animals of a given breed are the same. If we know an individual animal's complete genetic background, then we will be able to predict, not its actual disposition, but the disposition it will have if it gets affection and treatment that it needs to achieve its potential. Owners can then choose both their pets and pets' care more wisely than is possible today.

Should you have a concern regarding the health of your Beagle(s), you should contact your veterinarian. All information on this site is presented solely for educational and informational purposes and should not, at any time, be considered a substitute for seeking or receiving veterinary care for your Beagle(s).