Glossary of Genetic Terms

Alleles – One of two or more alternative versions of the same gene.

Amino acids – One of the chemical compounds that are the building blocks of proteins.

Autosomes – The name given to all chromosomes other than the two involved in determining the sex of an individual (the X and Y chromosomes). The dog has 38 pairs of autosomes and one pair of sex chromosomes.

Bases - There are four bases which join together to form DNA, Adenine, Guanine, Thymine and Cytosine, identified by their initials A, G, T and C. The bases join end to end to give a molecule of DNA. These bases join in a specific sequence and it is this base sequence that represents the genetic plan.

Candidate gene – A gene involved in a particular inherited disease in the dog which has been identified because the same gene is known to be the cause of a similar disease in man or other animals.

Carrier – With regard to hereditary disease this is a dog that carries a recessive, mutant allele that is matched by the presence of a normal allele. On average, it will pass on this mutant allele to half of its offspring.

Cells – One of the tiny living units from which organisms are made.

Cell membrane – The thin protective membrane that surrounds a cell.

Characteristic – A feature such as brown or blue eyes.

Chromosome – This is the body that carries the DNA within the nucleus. A thread of DNA runs along the length of each chromosome carrying individual genes.

Code – Cells use the genetic code to convert the DNA’s sequence of bases into a sequence of amino acids.

Congenital – Present at birth. May be inherited, but not necessarily.

Cytoplasm – The thick fluid that forms most of the inside of a cell.

DNA (Deoxyribonucleic Acid) – The chemical found in the nucleus of a cell that makes up chromosomes and genes. DNA consists of two chemical strands which twist around each other in the form of a helix. Each strand is made up by the joining together of the chemical units called bases.

DNA Sample – DNA can be collected in a number of ways. The most common methods used with dogs are by blood sample or a scraping of cheek cells, this is called a buccal sample.

Dominant Mutation – A mutation that can express itself when present only as a single copy, even in the presence of a normal allele.

Effective Population Size – The number of breeding animals in a hypothetical population that would deliver the same rate of inbreeding as the population in question

Enzyme – A type of protein found in the body that greatly speeds up the rate of chemical reactions inside and outside cells.

Gamete – A reproductive cell. At fertilisation, the male gamete (the sperm) and female gamete (the egg), unite and the genetic material combines.

Gene – A part of the DNA which controls the hereditary characteristics of an organism. Individual genes consist of a unique sequence of about 2000 bases which permits the cell to make a particular protein. Each individual has two sets of genes (one set from each parent) and passes this on to each of its offspring.

Genetic – Describes something to do with genes and inheritance.

Gene pool – All of the genes that exist within an inbreeding population.

Genome – A complete set of chromosomes, i.e. genes within a living organism.

Genotype – The genes found in the cells on an individual. The genetic makeup of an individual will influence the appearance of phenotype of the individual.

Heritability–The transmission, or passing on, of features controlled by genes from both parents to their offspring. The proportion of phenotypic variation that is due to genetic variation.

Heterozygous – An individual that has two different alleles of a gene for a particular characteristic. If one allele is recessive and the other dominant, then the effect caused by the dominant allele will be apparent.

Inbreeding – The breeding of individuals more closely related than average in the population.

Homozygous An individual that has identical alleles for a particular characteristic. Recessive characteristics will only show if an individual is homozygous for that characteristic.

Locus – Position on matching maternal and paternal chromosomes at which alleles of the same gene are found.

Marker – A component of a genetic map which uniquely identifies a locus.

Maternal – Something belonging to, or coming from, the mother (dam)

Microsatellite – A region of DNA which possesses an unusual base sequence where, two, three or four bases are continually repeated.

Monogenic – A characteristic controlled by a single gene.

Mutation – A change in the base sequence of DNA caused by an error in copying or some other factor. A mutation may be passed onto offspring.

Nucleus – The control centre of the cell which contains the chromosomes.

Paternal – Describes something belonging to, or coming from the father (sire).

Phenotype – The phenotype is the physical expression of an individual’s genotype. O bservable, or measurable, properties of an organism, e.g hip score, weight.

Polygenic – Descriptive of a trait which is under the control of many genes.

Protein – One of a group of chemical substances that build and run cells. Proteins are built of amino acids using instructions encoded in genes.

Recessive Mutation – A mutation that is masked by the presence of a normal counterpart. These are only expressed when there are two copies of the mutation.

Selection – The process of varying relative individual reproductive success in propagation of a population.

Sex chromosomes – Chromosomes involved in determining the sex of the animal, i.e. females have two X chromosomes and males posses one X and one Y chromosome.

Sex linked inheritance – Inheritance of characteristics that are determined by genes present on either the X or Y chromosome.

Somatic – All cells in the body apart from the reproductive cells (gametes).

go to top