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.
As mentioned, sickle-cell anemia is the result of a change in a single nucleotide, and it represents just one class of mutations called point mutations. Changes in the DNA sequence can also occur at the level of the chromosome, in which large segments of chromosomes are altered.lthough the haploid human genome consists of 3 billion nucleotides, changes in even a single base pair can result in dramatic physiological malfunctions. For example, sickle-cell anemia is a disease caused by the smallest of genetic changes.