Another form of genetic inheritance that is associated with disease susceptibility is that of chromosome abnormalities. This condition is related to the features of the chromosomes, including the rearrangements of segments of the chromosomes and the number of copies of each chromosome. For example, a specific organism may lose the ability to generate healthy offspring if this animal has lost at least one chromosome from the entire chromosome set.
The loss of at least one chromosome may result in an unbalanced segregation of chromosomes during mitosis and thus the daughter cells will not carry the same number of chromosomes. There are also cases wherein an organism has an extra copy or an extra set of chromosomes and this condition is known as polyploidy. In this scenario, the presence of an extra copy of a chromosome or an entire chromosome set will result in abnormal segregation and possibly misalignment of chromosomes during the cell cycle.
Mitochondrial inheritance is also another mode of genetic inheritance that influences disease susceptibility. The mitochondria of cells also contain DNA which is different from that present in the nuclei of cells. In addition, mitochondrial DNA generally contains genes for specific biochemical reactions of the body, including the generation of proteins that are responsible for maintaining the oxygen levels in the body. Since mitochondria are located within the cytoplasm of every cell, any mutations that occur in the mitochondrial genome are transmitted to the offspring through the maternal route.
It should also be understood that fertilization of an egg by a sperm occurs through the integration of the sperm’s DNA with the egg’s DNA, yet all the mitochondrial DNA of the egg are transmitted in whole to the daughter cells. Disease susceptibility may thus be influenced by genetic inheritance, especially through the type and nature of mutations that are present in the cells of an organism (Stear et al. , 2007). There are currently a number of genetic tests that facilitate the identification of genetic abnormalities in different types of organisms.
Once a genetic disorder has been identified, it will be easier to determine that mode of transmission of this disease to the offspring. In the field of veterinary medicine, it is important to know the genetic abnormalities that are associated to particular diseases. When a specific genetic disease has been positively identified in an organism, it is best to review and assess how its offspring is managed, as it is most likely that the same disorder will be developed in the next generation.
In addition, proper management and care should be given to organisms of known genetic disorders in order to prevent the progression of the disease. References Coltman, D. W. , Wilson, K. , Pilkington, J. , Stear, M. J. and Pemberton, J. M. (2001). A microsatellite polymorphism in the gamma interferon gene is associated with resistance to gastrointestinal nematodes in a naturally-parasitized population of Soay sheep. Parasitology, 122, 571–582. Donaldson, J. , van Houtert, M. F. J. and Sykes, A. R. (1998). The effect of nutrition on the periparturient parasite status of mature ewes.
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