Whether it is brand-new or years old, a mattress too soft for your comfort level may make for many restless nights. As long as the mattress is in good shape, there's no need to replace it to achieve the desired level of firmness.Instead, purchase a firm topper, slide a bed board beneath the mattress, or add extra support to the bed frame itself. sheet of plywood cut to the same size as the mattress offers support for a mattress that has lost some of its firmness. Slide the plywood between the mattress and box spring.
Human cells normally contain 23 pairs of chromosomes, for a total of 46 chromosomes in each cell (illustration). A change in the number of chromosomes can cause problems with growth, development, and function of the bodyâs systems.
The most well known and most common autosomal abnormality is Down syndrome. This is a mild to severe form of mental retardation accompanied by distinctive physical traits. People with Down syndrome have an irregularity with autosome pair 21. In most cases, there is an extra chromosome (i.e., trisomy 21). More rarely (3-5%), there is a structural modification in this chromosome. Specifically, there is a translocation of all or part of chromosome 21 to chromosome 14 or 15. The actual genes on chromosome 21 that are responsible for Down syndrome are now being identified. It is thought that there are at least 350 genes involved. About 2-4% of the people with Down syndrome are genetically mosaic. That is, some of their cells have chromosome 21 trisomy while others do not, resulting in generally milder symptoms. The translocational type of Down syndrome also usually has less severe symptoms.