Genetic Conditions

RECESSIVE GENETIC CONDITIONS

Recessive Genetic Conditions, Arthrogryposis Multiplex (AM), Hydrocephalus (NH), Contractural Arachnodactyly (CA) and Developmental Duplications (DD).

Putting undesirable Genetic Recessive Conditions in perspective
All animals, including humans, carry single copies (alleles) of undesirable or ‘broken’ genes. In single copy form, these undesirable alleles usually cause no harm to the individual. But when animals carry 2 copies of certain undesirable or ‘broken’ alleles it often results in bad consequences. Advances in genomics have facilitated the development of accurate diagnostic tests to enable the identification and management of numerous undesirable or ‘broken’ genes. Angus Australia is proactive in providing its members and their clients with relevant tools and information to assist them in the management of known undesirable genes and our members are leading the industry in their use of this technology.

What are AM, NH, CA and DD?

AM, NH, CA and DD are all recessive conditions caused by ‘broken’ alleles within the DNA of individual animals. When a calf inherits 2 copies of the AM or NH alleles their development is so adversely affected that they will be still-born.
In other cases, such as CA and DD, calves carrying 2 copies of the broken allele may reach full-term. In such cases the animal may either appear relatively normal, or show physical symptoms that affect their health and/or performance.

How are the conditions inherited?

Research in the U.S. and Australia indicates that AM, NH, CA and DD are simply inherited recessive conditions. This means that a single gene (or pair of alleles) controls the condition. For this mode of inheritance two copies of the undesirable allele need to be present before the condition is seen; in which case you may get an abnormal calf. A more common example of a trait with a simple recessive pattern of inheritance is black and red coat colour.

Animals with only one copy of the undesirable allele (and one copy of the normal form of the allele) appear normal and are known as ‘carriers’.

What happens when carriers are mated to other animals?

Carriers, will on average, pass the undesirable allele to a random half (50 %) of their progeny.
When a carrier bull and carrier cow is mated, there is a 25% chance that the resultant calf will inherit two normal alleles, a 50% chance that the mating will result in a carrier (i.e. with just 1 copy of the undesirable allele, and a 25% chance that the calf will inherit two copies of the undesirable gene.

If animals tested free of the undesirable gene are mated to carrier animals the condition will not be expressed at all. All calves will appear normal, but approximately half (50%) could be expected to be carriers.

How is the genetic status of animals reported?

DNA-based diagnostic tests have been developed which can be used to determine whether an individual animal is either a carrier or free of the alleles resulting in AM, NH, CA or DD.

Angus Australia uses advanced software to calculate the probability of (untested) animals to being carriers of AM, NH, CA or DD. The software uses the test results of any relatives in the calculations and the probabilities may change as new results for additional animals become available.

The genetic status of animals is being reported using five categories:

AMF

Tested AM free

AMFU

Based on pedigree AM free – Animal has not been tested

AM__%

__% probability the animal is an AM carrier

AMC

Tested AM-Carrier

AMA

AM-Affected

For NH, CA and DD, simply replace AM in the above table with NH, CA or DD.

Registration certificates and the Angus Australia web-database display these codes. This information is displayed on the animal details page and can be accessed by conducting an ‘Animal Search’ from the Angus Australia website or looking up individual animals listed in a sale catalogue.

GENETIC CONDITIONS CODES
• Arthrogryposis Multiplex (AM)
• Contractual Arachnodactyly (CA)
• Neuropathic Hydrocephalus (NH)
• Red gene (RD)
• Mannosidosis (MA)
• Developmental Duplications (DD)

DESCRIPTION OF THE GENETIC TEST CODES

AMF

CAF

NHF

RDF

MAF

DDF

Indicates that the sample submitted for this animal has been tested and found to be free of the causative mutation responsible for the genetic condition (AM, CA, NH, RD, MA or DD). This animal is homozygous free, meaning that it has two copies of the normal variant (or allele) of the gene.

AMC

CAC

NHC

RDC

MAC

DDC

Indicates that the sample submitted for this animal has been tested and found to be a carrier of the causative mutation responsible for the genetic condition (AM, CA, NH, RD, MA or DD). This animal is heterozygous for the mutation, meaning that it has one mutant allele and one normal allele. This animal could pass the mutation to approximately half of its progeny.

AM_%

CA_%

NH_%

DD_%

Indicates that  based on pedigree information supplied by the breeder of the animal, the animal has a chance to be a carrier of the mutation responsible for the genetic condition (AM, CA, NH or DD) but has not been tested. The higher the indicated percentage, the larger the chance the animal may be a carrier. To verify the status of this animal, Angus Australia recommends that  testing be undertaken prior to using this animal for breeding  purposes.

AMFU

CAFU

NHFU

DDFU

Indicates that, based on pedigree information supplied by the breeder of the animal, the animal is expected to be free of the mutation responsible for the genetic condition (AM, CA, NH or DD) but has not been tested. This animal has not been tested for the causative mutation and Angus Australia gives no guarantee as to the animal’s “free” status.

AMA

CAA

NHA

DDA

Indicates that the sample submitted for this animal has been tested and the animal found to be homozygous for the mutation responsible for the genetic condition (AM, CA, NH or DD) and have two copies of the mutant variant of the gene.Note, for some recessive conditions such as DD, not all homozygous animals appear to displayphenotypic expression of the condition.

Disclaimer: Angus Australia makes no statements, representations or warranties about the accuracy or completeness of, any information relating to the status of a particular animal; and, disclaims all responsibility for information and all liability (including without limitation, liability in negligence) for all expenses, losses, damages, and costs you may incur as a result of information being inaccurate or Incomplete in any way for any reason.

Genetic test results are based on samples provided by breeders.

CLICK HERE to download the pdf version

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