There has not been any detailed information regarding genetic disorders in inbred animals. If there are, it is not known whether they serve as a threat and contribute to the small numbers in populations of inbred animals.
Even if this is not my field of expertise, I think you should look into population dynamics linked to the proportion of homozygous in the population.
If inbred animals suffer genetic diseases, we can postulate that they have a low survival. Thus, our power of detection of genetic diseases might also be very low and that foetus presenting those diseases die before birth or at young ages.
It is the inbred nature of the Tasmanian Devil that led to their genomes \similar enough for the first case of an infectious cancer (Devil facial tumour disease from bighting) to reduce to population by uoto 90% and if niot mnaged possible extinction
They do. For instance, think of the royal families: The British royal family was once known for certain inherited disorders like hemophilia and porphyria.
Inbreeding within a species always result in the loss of genetic diversity within a population by means of an increase in homozygosity in the population. For instance, in case of tigers (one of the most inbred animals in captivity) constant inbreeding practices have been reported resulting in mutations such as immune deficiency, scoliosis, cleft palates, mental impairments, strabismus, and early death.
They certainly do! In fact genetic diseases are likelier in inbred populations, as normally unexpressed recessive lethal alleles are likelier to be expressed due to homozygosity.
As everyone has noted, inbred lines do in fact suffer genetic diseases. However, it is possible, given sufficient time, to purge most deleterious alleles provided the lineage doesn't go extinct first. You have to start with a large number of replicate lineages because most will go extinct and it takes quite a long time. This should be described in most genetics textbooks. Of course, even if you purge the deleterious alleles and remove most genetic diseases, what you end up with will have such low genetic diversity that it is susceptible to any disease that comes along. I know the late American geneticist James Crow was very interested in inbreeding and genetic diseases. A recent article (Gulisija and Crow 2007. Evolution 61(5):1043-1051) has a pretty good list of papers on purging.
The positive outcome of inbreeding is strongly dependent on the 'purity' of the gene pool of the inbred animals; and this is where the advantage lies. But if inbreeding is without cognizance of certain key characteristics of the gene pool as evident in population of interest the outcomes may not be so favorable.
"Why don't inbred animals suffer genetic diseases? Are their genes unaffected by genetic disorders? "
why do You ask?
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