Glossary

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ALLELE:

An alternative version of a gene. Some genes have a considerable number of alleles. Dogs which carry the same allele in duplicate are said to be homozygous for that gene while those that carry two versions(two different alleles) for that gene are said to be heterozygous.

ALLERGY:

Immunological hypersensitivy to certain foreign antigens.

AMINO ACID:

The “building blocks” of proteins. There are 20 amino acids.

ANOMALY:

An abnormality.

ANTIBODY:

A protein produced in response to an antigen; an important component of the immune system.

AUTOSOME:

Any chromosome other than the sex chromosomes X and Y. An autosomal trait is one whose gene(s) is not on the X or Y chromosome and therefore, can be transmitted to either sex.

BASE:

A component of a nucleic acid molecule. The bases are adenine, thymine, guanine, cytosine and uracil. They are designated by the abbreviations: A, T, G, C and U.

BASE PAIR:

Two bases, opposite each other in a double-stranded nucleic acid molecule. The only possible pairs are A-T, G-C, and A-U.

CARRIER:

An individual which carries a recessive allele masked by a dominant. The individual appears normal for a given trait, but carries a gene capable of producing an undesirable trait.

CELL:

The smallest unit of living matter capable of maintenance and reproduction. It contains DNA and an organized set of chemical reactions necessary for self perpetuation.

CENTRAL DOGMA:

The concept describing the flow of hereditary information. Within one generation information flows from DNA to RNA to protein to produce the ultimate phenotype; between generations, DNA replicates itself precisely.

CHARACTERISTIC:

An attribute, structure or function that can be observed due to action of one or more genes.

CHROMOSOME:

A linear gene-containing body composed of DNA complexed with protein. Chromosomes usually occur in pairs. They are located in the nucleus of every cell. There are 78 total chromosomes (39 pairs) in the dog.

CODON:

A trio of nucleotides which code for a specific amino acid. There are 64 possible codons and 20 amino acids. More than one codon can code for the same amino acid. Some of these codons also act as stop signals to stop production once the correct number of amino acids have produced a protein.

COMPLEMENTARY BASE PAIR RULE:

Only certain nucleotides can align opposite each other (like a lock and key) in the two strands of DNA. G pairs with C; A with T (or U).

CONGENITAL:

Present at birth.

DIPLOID:

Having two sets of chromosomes; one set from the mother and the other set from the father.

DNA:

Deoxyribonucleic acid. A long, chain-like molecule that consists of two complimentary strands. The sub-units are the four nucleotide bases (A, T, C, G) each attached to a pentose sugar (deoxyribose) and to a phosphate. The arrangement of the sub-units is used to store all the information necessary for life.

DOMINANT GENE/TRAIT:

The ability of an allele of a gene to produce the same characteristic, whether paired with an identical allele or one that is dissimilar. It “hides” or “blocks” the effect of the recessive allele.

EGG:

Germ (reproductive) cell produced by a female.

ENZYME:

A protein molecule whose function is to catalyze (accelerate) a biological chemical reaction.

FRAMESHIFT:

A mutation caused by the addition or subtraction of one or more nucleotides. The reading frame (3 nucleotides) will be altered.

GAMETE:

A germ cell, either an egg or a sperm.

GENE:

A distinct unit of inheritance; a sequence of DNA that specifies a particular trait of an organism.

GENOME:

The entire gene complement possessed by a cell or individual.

GENOTYPE:

The genetic constitution of an individual in contrast to its appearance (phenotype).

GERM CELLS:

Sperm and ova.

HAPLOID:

Having only one chromosome of each homologous pair. Sperm and ova are haploid cells. All other cells in the body are diploid (they have pairs of chromosomes).

HERITABILITY:

The proportion of parental superiority which is transmitted to the offspring. The heritability can vary from 0-100%. Traits of high heritability are those above 50%, medium from 20-50% and low are below 20%.

HETEROZYGOUS (HETEROZYGOTE):

Having two different alleles of a gene at a specific locus, i.e., the dominant and recessive genes are both present. These individuals are often called carriers.

HOLANDRIC:

Genes carried on the Y chromosome.

HOMOLOGOUS:

Regions of DNA molecules that have the same nucleotide sequence.

HOMOZYGOUS (HOMOZYGOTE, n.):

Having matching alleles of a given locus. They can be either dominant or recessive but are an identical pair.

INBREEDING:

Mating closely related animals.

INCOMPLETE DOMINANCE:

The recessive allele is not masked completely by the dominant allele. Both will have an effect on the phenotype.

KARYOTYPE:

The total chromosomal complement of an individual; usually represented as a formal arrangement of photographed chromosomes in a single cell.

LINEBREEDING:

The mating of later generations back to some ancestor or its descendants. Not as close as “inbreeding”.

LINKAGE:

Occurrence of two or more genes on the same chromosome. Linked genes are transmitted as a group of gametes.

LOCUS (LOCI, pl):

The position on a chromosome for a specific gene or genes.

MESSENGER RNA:

The molecule used to transmit information from a gene on DNA to a ribosome, where the information is used to make protein.

METABOLISM:

A collective term for all the chemical reactions involved in life.

MODIFIER:

A gene that alters the effect of a different gene. Modifiers may enhance or suppress a trait that they modify.

MOLECULE:

A group of atoms tightly joined together. The arrangement of atoms gives each molecule specific chemical and physical properties. A macromolecule, such as proteins, fats, carbohydrates and nucleic acids is a complex of smaller sub-unit molecules.

MONOGENIC:

Caused by a single pair of genes.

MUTANT:

An organism whose DNA has been changed; it is generally different from the dominant members of the population.

MUTATION:

A heritable change in the sequence of nucleotide bases in DNA due to an error in replication. It may or may not alter the phenotype in succeeding generations.

NUCLEOTIDE:

One of the building blocks of the nucleic acids. It has 3 components: a base, a sugar and a phosphate.

ORGANISM:

One or more cells organized in such a way that the unit is capable of reproduction.

PHENOTYPE (-TYPIC):

The observable appearance of an individual; the physical expression of the genotype.

PHOSPHATE(PO4):

A chemical unit joining four oxygen atoms to one phosphorus atom. The backbones of DNA and RNA are alternating phosphate and sugar units.

POLYGENIC:

The control of a phenotype trait by 2 or more genes.

PREPOTENT:

Having a strong tendency to endow offspring with a specific trait or traits.

PROBAND:

The first incidence of a trait in a genetically related group or family.

PROTEIN:

Long, chain-like molecules consisting of amino acid sub-units. Proteins function as enzymes (catalyzing chemical reactions) or as structural elements providing the cell with shape and form.

RECESSIVE:

An allele which expresses itself only when present in duplicate. Recessive genes and traits are hidden or masked by dominant genes or traits.

RESTRICTION ENDONUCLEASE:

An enzyme that cuts DNA at specific nucleotide sequence; functions as a protective mechanism and a research tool.

RESTRICTION FRAGMENT POLYMORPHISM (R.L.F.P.):

A region of DNA with different forms (sequences); the fragments created by restriction endonucleases will vary in size from one individual to another.

RIBOSOME:

Large, round structures where proteins are assembled. Ribosomes are composed of RNA.

RNA:

Ribonucleic acid. A long, chain-like molecule usually found as a single strand. The subunits are the four nucleotide bases (A, U, G and C), a pentose sugar(ribose) and a phosphate. The types of RNA are messenger RNA (mRNA), transfer (tRNA) and ribosomal RNA.

SEQUENCE:

The order of nucleotides in DNA or RNA.

SEX CHROMOSOMES:

Chromosomes that control the sex of an animal. Bitches have two x chromosomes; males have one X and one Y chromosome.

SEX-LINKED:

Refers to gene carried on the sex chromosome, usually the X.

SIMPLE TRAIT:

One which is determined by a single pair of alleles.

SPERM:

Germ cell produced by the male.

SUBUNIT:

One of the pieces that forms a part of a multi-component structure. A link in a chain or a brick in a wall.

SUGAR:

Molecule consisting of carbon, hydrogen and oxygen. The sugars in DNA and RNA have five carbons atoms. Glucose is a sugar containing six carbons.

SYNDROME:

A set of symptoms associated with one disease or pathological condition.

TEST CROSS:

A mating between a heterozygote and an individual homozygous for the recessive allele.

TRANSCRIPTION:

The process of converting information from DNA into information in messenger RNA.

TRANSFER RNA:

Small RNA molecule that positions amino acids in the correct order during protein synthesis.

TRANSLATION:

The process of converting the information in messenger RNA into protein.

ZYGOTE:

The fertilized egg.

References:

Burns, M., Fraser, M. N. Genetics of the dog. Philadelphia: J.B. Lipincott, 1966.

Drlica, K. Understanding DNA and gene cloning, 2nd ed. New York: John Wiley & Sons, 1992.

Falconer, D. Introduction to quantitative genetics, 2nd ed. New York: Longman Press, 1981.

Farnsworth, M.W. Genetics, 2nd ed. New York: Harper and Row, 1988.

Hutt, F.B., Genetics for dog breeders. San Francisco: Freeman Co., 1979.

Maxson, L. R., Daugherty, C.H. Genetics-a human perspective. Dubuque, IA: Wm. C. Brown, 1985.

Walkowicz, C., Wilcox, B. Successful dog breeding. New York: Arco, 1985.

Willis, M. B. Genetics of the dog. New York: Howell Book House, 1989.

Willis, M. B. Practical genetics for dog breeders. New York: Howell Book House, 1992.