Animal Search | AJSA | IGS | Fall Focus  |  ASF | Site Search

What Does it Mean to be a Carrier, Free, or Affected for Different Genetic Defects?

Print Friendly, PDF & Email

Many genetic defects are simple recessive traits, meaning it takes two bad alleles (versions of a gene) to see the condition. If an animal is tested free (for instance DDF means tested free for DD), the animal does not have one of these defective alleles. If the animal is a carrier (DDC) then that animal has one normal copy and one defective copy of the gene. If an animal is affected (DDA) then both copies of the gene are defective. Typically we would expect these affected animals to show the signs (phenotype) for that genetic condition. The only way to get affected animals is to mate a carrier bull to a carrier dam. In carrier to carrier matings, we expect 25% of the progeny to be free, 50% to be carriers and 25% to be affected.

In the case of DD, some animals have both defective copies of the gene but don’t show any sign of the genetic condition (this is called incomplete penetrance). With incomplete penetrance, some other factor is needed for the phenotype to display. This trigger may be environmental (nutritional, stress, etc.) or genetic (a second gene involved in the pathway).

 
Print Friendly, PDF & Email

Down to the Genes Series

Why an Animal May Not Have GE (Genomically Enhanced) EPDs

January 29, 2021 DNA
Heading into the new year and the start of bull sale preparation, one of the DNA Department’s most frequently asked questions is why an animal doesn’t have GE (genomically-enhanced) EPDs after completing a genomic test. This article explores the general process and common reasons why GE may not appear on an animal’s record in Herdbook. The Process After an animal is tested on a genomic panel…

Visit the ASA FB Page                   

Top