Trisomy 21: Down Syndrome

This person is 3 copies, one of which is 2 copies. This is called tri-nature. The chromosome affected by this individual is chromosome 21. Chromosome 21 is the smallest chromosome in humans, but altering it can cause many problems. This includes several kinds of cancer such as leukemia. It can also affect mental development and growth. As this person has three chromosomes, not two, this means that they have Down's syndrome. The doctor was identified as chromosome 21 trisomy in 1959.

Trisomy is the most common aneuploidy. In trisomy, there are extra chromosomes. The general trisomy is trisomy 21 (Down syndrome). Other trisomies include 13 trisomy (Patau syndrome) and 18 trisomy (Edwards syndrome). Monosomy is another type of aneuploidy in which the missing chromosome is present. Common monosomy is a Turner syndrome in which female X chromosome is missing or damaged. Autosomal dominant disease is caused only by the parent's defective gene. "Allogeneic" means that the defective gene is located on any chromosome that is not a sex chromosome (X or Y). If one parent has this gene, each couple's child has 50% likelihood of inheriting the disease. An example of autosomal dominant disease is Huntington's disease.

Down syndrome is a hereditary disorder caused by trisomy of human chromosome 21. Down syndrome is a common chromosomal abnormality in human mental retardation. It is caused by three types of chromosomal abnormalities, free trisomy 21, translocation Down syndrome and mosaic down syndrome. Most patients with Down's syndrome experience neuropathology like Alzheimer's disease, such as dementia, neurofibrillary tangles. Genes containing SOD-1, DSCR1, APP gene and S100B on chromosome 21 are deeply involved in the relationship between Down's syndrome and Alzheimer's disease. In addition to the genes involved, other factors such as oxidative stress and hormones are also described in this review.

Trisomy 18, also known as Edwards syndrome, is the second most common trisomy following trisomy 21 (Down's syndrome). It appears in one of 5,000 births due to the presence of an additional chromosome 18, similar to Down's syndrome. As the age of the mother goes up, it becomes more common. Infants born in trisomy 18 have important clinical features, including stunts, craniofacial, limbs, heart, and kidney abnormalities. Half of all infants with Edwards syndrome will die within the first week and only 1-5% of infants will die within the first year