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.
That's the number of chromosomes in the nuclei of a person with Down syndrome and certain other genetic conditions. Most human cells have 46 chromosomes, but occasionally, a glitch in cell division results in a cell with too few or too many chromosomes. When this happens in egg or sperm cells, the child can have an abnormal number of chromosomes. People with Down syndrome have an extra copy of chromosome 21, one of the smallest chromosomes in the genome. 1953 DNA is shaped like a spiral staircase that can be split, copied and passed on to future generations.