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.
Research shows that three types of chromosomal changes can lead to Down syndrome. 1  Complete trisomy 21. 2  In this case, an error during the formation of the egg or the sperm results in either one having an extra chromosome. 3  So after the egg and sperm unite, the resulting cells will also have three copies of chromosome 21. The complete extra copy of chromosome 21 is in all of the person's cellsâor a complete trisomy. Complete trisomy 21 is the cause of about 95% of Down syndrome cases. Mosaic trisomy 21.