AlleleAlternative form of a gene or DNA sequence. Variations in clinical traits and phenotypes are allelic if they arise from the same gene sequence or locus and nonallelic if they arise from different gene sequences of different loci.
AtaxiaIs a condition of the nervous system that results in cerebellar degeneration and death in Belgian Shepherds. Symptoms typically begin at around 4 – 6 weeks of age and include a progressive loss of coordination. The 2 most common forms are known as Spongy Degeneration with Cerebellar ataxia, type 1 or type 2.
CongenitalA defect or condition present at birth.
Dominant ModeA mode of inheritance in which a given trait is expressed when either parent passes on the allele that causes the trait to be transmitted to an offspring.
HaplotypeThe combination of linked marker alleles (may be polymorphisms or mutations) for a given region of DNA on a single chromosome.
HeterozygoteA dog (or any animal) that has copies of 2 different forms of a particular gene, having inherited a different form from each parent.
HeterozygousA dog (or any animal) that has copies of 2 different forms of a particular gene, having inherited a different form from each parent.
HomozygoteA dog (or any animal) that has 2 copies of an identical form of a particular gene, having inherited the same form from each parent.
HomozygousA dog (or any animal) that has 2 copies of an identical form of a particular gene, having inherited the same form from each parent.
HSF4 GeneFrom a family of genes called heat shock transcription factors that regulate the expression of proteins in response to different stresses, including temperature, oxidation, and infections. Different mutations of HSF4 are known to produce both dominant and recessive cataracts.
LensA biconvex, transparent structure of the eye consisting of a capsule, cortex, and nucleus. The lens refracts light transmitted to the retina and functions to adjust the focal length so that objects at different distances can be sharply seen.
Lenticular sclerosisThe transparent, bluish haze that develops in the lens of older dogs. It is considered a normal condition in middle-age to senior aged dogs. Vision is usually not affected. Lenticular sclerosis is believed to be caused by hardening of fibers that compose the cortex of the lens.
LocusIn genetics, a fixed position or “address” on a chromosome at which a particular gene (or gene sequence) is located. (dv)
MutationA permanent alteration of the DNA sequence that makes up a gene, such that the sequence differs from what is found in most individuals. Generally, mutations refer to changes that alter the gene in a negative sense causing the protein product of the gene to have an altered function, though not all mutations will disrupt function.
Null HypothesisIn statistics, the null hypothesis presumes that there is no difference between the groups. It is frequently used as a starting point to begin gathering evidence to either prove or disprove that the groups are identical with respect to the attributes being studied. The null hypothesis is generally assumed to be true until subjected to testing and then rejected on the basis of empirical evidence. (dv)
PenetranceThe proportion of a population carrying a particular allele that also expresses the phenotypic trait associated with that allele. If an allele is highly penetrant, the trait will be observable in almost all individuals carrying that allele. Alleles having low penetrance are much less likely to be expressed as the phenotypic trait.
Popular Sire EffectRefers the consequences for a population when a subset of males produces a disproportionately large number of offspring. Deleterious recessive alleles can be carried by any organism, but these alleles tend not to affect many individuals at the population level when all males have a similar chance of producing offspring. Popular sires are able to pass on more of their particular recessive alleles, both good and bad, at the expense of males who do not sire offspring. As deleterious alleles passed
Punnett SquareA diagram representing the genotypes of offspring given particular sets of maternal and paternal alleles. Punnett squares are used to determine the probabilities that a single trait is expressed in offspring based on the combination of alleles contributed by both parents. (dv)
Recessive ModeA mode of inheritance in which a given trait is expressed only when both parents pass on to their offspring the necessary alleles for causing the trait.
SDCA1’Spongy degeneration with cerebellar ataxia’, the official name for the 2 forms of ataxia identified so far in Belgian Shepherds. It causes a progressive loss of coordination and death in all puppies that are homozygous for either of the 2 mutations known to cause it.
SDCA2’Spongy degeneration with cerebellar ataxia’, the official name for the 2 forms of ataxia identified so far in Belgian Shepherds. It causes a progressive loss of coordination and death in all puppies that are homozygous for either of the 2 mutations known to cause it.
SuturesAs fibers within the cortex of a lens grow during fetal development, an initial pattern emerges in which Y-shaped zones of intersecting fibers called sutures appear near the anterior and posterior poles of the lens. In normal lens development, sutures disappear as the arrangement of cortical fibers becomes more complex during gestation. However, atypical lens development can result in congenital formation of cataracts at the sutures or small opacities at the outer tips of the sutures called punctate cataracts.