Down Syndrome in Dogs
Down syndrome in dogs was originally thought to be the only chromosomal defect in all mammals. Usually the pregnant mother aborts or rejects the fetus because of the abnormality, a number one reason down syndrome in dogs or animals is not a problem we hear much about.
However, because of the findings of the Dog Genome Project we have found that the domesticated dog is a very close evolutionary relation to the human. By understanding the genetics of the dog, disease mappings have resulted in over 1,800 DNA markers in dogs and 320 dog genes.
It has been found that there are underlying diseases shared between the dog and people — a skin disease known as ichthyosis, muscular dystrophy, von Willebrand’s disease, cancer, diabetes, and epilepsy. Basically, it has been found that any disease humans get, the dog can get also.
“We dog researchers are not working in the dark,” says Keith E. Murphy of Texas A&M University, whose team recently sequenced the keratin gene, KRT2p, and mapped it to chromosome 27 of the dog. “The great progress in human genetics means that if you have a disease that presents the same way in humans and dogs, you can almost go straight to the gene in the dog.”
Studies done by the Human Genome Project are being done by researchers of the human chromosome 21, along with studies at the Dog Genome Project. Over 95% of all cases list the cell as having two 21 chromosomes instead of just one, consisting of 200 to 250 genes. Down syndrome is considered a chromosomal abnormality because of an “extra copy of genetic material” placing itself on the 21st chromosome, resulting in a trisomy of the 21st chromosome.
The projects have sequenced the base pair that forms chromosome 21, the second human chromosome ever to be fully sequenced. Other diseases associated with genes of this chromosome are Alzheimer’s Disease, Leukocyte adhesion deficiency, Majewski osteodysplastic primordial dwarfism type II, homocystinuria, Roman-Ward syndrome, and Erondu-Cymet syndrome. According to the Dog Genome Project, ” On the evolutionary tree, the dog is somewhere between humans and mice. Sequences that are conserved in all three species are likely to be in the human genome for a reason.”
The studies have also found that the reasons dogs are loyal to humans is because it is the same type of relationship that corresponds to their natural social patterns. Each individual has a rank, with the dog always aware of its position within a group. In fact, the dog genome is the same as the human genome but divided into 70 pieces with a greater number of chromosomes.
The mapping of the 21 chromosome in dogs has demonstrated not downs syndrome, but a genetic diversity unlike any other mammalian on earth. The huge diversity of the canine has been influenced by the human’s direct breeding — channeling it into a storage of inherited diseases, behaviors and morphologies. This has made possible the dog’s genome sequencing and SNP mapping to allow us to see the similar genetics of disease and normal biology between dogs and mankind.
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