Understanding Modes of Transmission

Exemple de rapport

In your genetic test reports, the mode of transmission is always indicated for each disease or trait tested. This detail is essential to understand how a condition can be passed from one generation to the next.

By clicking on the transmission modes listed below, you will access a detailed explanation of each one:

Recessive

• Autosomal recessive:

  A genetic disease or trait appears only if the animal inherits two copies of the mutated gene (one from each parent). Carriers (with only one copy of the mutated gene) are usually healthy but can pass the mutation on to their offspring.
  

  Example: Progressive Retinal Atrophy (PRA) in many breeds.

  
  
  
  

Dominant

• Autosomal dominant:

  A single copy of the mutated gene (inherited from one parent) is enough for the disease or genetic trait to appear. These conditions are often observed in every generation.

  
  

  Example: Achondroplasia (a form of dwarfism) in certain breeds.
  

Incomplete Dominant (or semi-dominant)

• Ce mode de transmission signifie qu’un individu avec une seule copie du gène muté (hétérozygote) présente une forme intermédiaire du trait ou de la maladie, tandis qu’un individu avec deux copies (homozygote) manifeste une forme plus sévère ou complète.

  
  

  Exemple : Le locus merle chez les chiens, où le double merle peut entraîner des problèmes de santé.
  

Sex-linked

• X-linked recessive: The mutation is carried on the X chromosome. Males (having only one X chromosome) are more likely to be affected, while females can be carriers without showing symptoms.

  Example: Hemophilia in dogs.
  

• X-linked dominant: A single copy of the mutation on the X chromosome can cause the disease, affecting both sexes but often more severely in males.Rare example in dogs and cats.
  

Polygenic (or multifactorial)

• This mode of transmission involves multiple genes and sometimes environmental factors. The risk depends on the combination of inherited genetic variations and external influences.

  Example: Hip dysplasia.

Autosomal recessive transmission with incomplete penetrance:

• The disease appears when two mutant copies are present, but not all dogs with this genotype will necessarily develop symptoms. Expression can range from absent to severe.

Why is this important?

Knowing the mode of transmission of a disease or trait helps you:

• Assess the risks for offspring.

• Understand the implications for breeding or health.

• Make informed decisions for your animals.