The Afrikaner: equipped to beat climate change

The Afrikaner beef cattle breed's outstanding plasticity enables it to perform optimally despite the negative consequences of climate change. Georgette Pyoos, a junior researcher in the Animal Breeding and Genetics Department at the Agricultural Research Council, spoke to Annelie Coleman about plasticity and its value.

- Annelie Coleman

What is plasticity in cattle?

Phenotypical plasticity is the ability of an individual animal to change in response to stimuli or inputs from the environment. The response may or may not be adaptive, and it may involve a change in morphology, physiological state, or behaviour, or a combination of these. The phenotype is all of the physical characteristics of an organism other than its genes.

How is plasticity determined and measured?

Several analytical models are used to explain the genetic basis of plasticity responses. The main and not mutually exclusive ones are:

• Over-dominance. Here, the plasticity is an opposite function of the number of heterozygous loci. Heterozygous, as related to genetics, refers to having inherited different versions (alleles) of a genomic marker from each biological parent. Thus, an animal that is heterozygous for a genomic marker has two different versions of that marker.
• Pleiotropy. This is the phenomenon of a single gene influencing two or more distinct phenotypical traits. In this case, plasticity is a function of the differential expression of a gene in different environments due to some pleiotropic effect. It refers to the influence of a gene on multiple and partially unrelated traits.
• Epistasis. This refers to the interaction between genes that influences a phenotype. The plasticity may be due to the epistatic interaction between genes determining the degree of response to environmental influences and others causing the average expression of a trait.