the donor cell nucleus. These anomalies may be macroscopic (e.g., anatomical abnormalities, difference in size or growth rate, reduced fertility, morbidity, mortality) or they may be more subtle in nature. Potential subtle hazards would allow an animal clone to develop with apparently normal appearance and functions, but with sub-clinical physiological changes.[1] These include alterations in clinical chemistry, hematology, or changes in physiological set-points (e.g., changes in hormone levels). For food consumption risks, relevant subtle hazards that might result from inappropriate or incomplete reprogramming include alterations in the expression of key proteins affecting the nutritional content of food, possibly leading to dietary imbalances. Similar hazards arise in animals generated via other ARTs or natural breeding. The goal of this risk assessment is to determine whether any unique hazards arise that are not noted in comparators, or have not been identified in cattle, swine, sheep, or goats produced via other ARTs or natural breeding.
To address animal health and food consumption risks associated with cloning, two complementary approaches were employed. First, information on the health of animal clones was evaluated within a framework developed by CVM called the Critical Biological Systems Approach (CBSA). For food consumption risks, the CBSA was applied in combination with a second approach referred to as Compositional Analysis. Following review of all of the available data using the CBSA and Compositional Analysis, a weight of evidence approach was then used to draw conclusions regarding risks to animals associated with cloning, and risks to humans from consuming foods produced by animal clones.
The CBSA: This approach divides the life cycle of an animal clone into five functional developmental nodes. Developmental Node 1 incorporates the initial technical steps involved in SCNT (cell fusion) and continues through fetal development. Developmental Node 2 encompasses the perinatal period, including labor induction in the dam, delivery, and the critical few days after birth. The third developmental node, Juvenile Development and Function, covers the period of rapid growth between birth and the onset of puberty. The Reproductive Development and Function Node (Developmental Node 4) includes puberty and reproductive function throughout the reproductive life of clones. The Post-Pubertal Maturation Node (Developmental Node 5) consists of all non-reproductive functions of sexually maturing or mature clones, including growth, weight gain, disease frequency, aging, and, where available, lifespan.
The nature of each component of the risk assessment (i.e., animal health or food consumption risks) shaped the manner in which the available data were evaluated using the CBSA. For example, identification of adverse outcomes for animal health included both the animal clone
- ↑ Such subtle hazards are not typically included in standard food safety assessments.
Animal Cloning: A Risk Assessment
