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.
Scientists have successfully turned off the chromosome defect that causes Down syndrome. Down syndrome, also called Trisomy 21, is a genetic condition in which a person has three copies of chromosome 21, resulting in 47 chromosomes instead of 46. It is one of the most common causes of human birth defects. According to the Centers for Disease Control and Prevention, Down syndrome had an incidence rate of 11.8 babies per 10,000 live births from 1999 to 2003.