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.
However, these mistakes are rare, and the cell has repair mechanisms that can repair some damage. - Sometimes a permanent change occurs in a cell's DNA and this is called a mutation. - Because a mutation in a gene causes a change in the protein that is made, the enzyme is nonfunctional. Types of mutations - Mutations can range from changes in a single base pair in the coding sequence of DNA to the deletions of large pieces of chromosomes. - Point mutations involve a chemical change in just one base pair and can be enough to cause a genetic disorder. - A point mutation in which one base is exchanged for another is called a substitution. - Most substitutions are missense mutations, where the DNA code is altered so that it codes for the wrong amino acid. - Other substitutions, called nonsense mutations, change the codon for an amino acid to a stop codon. Nonsense mutations cause translation to terminate early. Nearly all nonsense mutations lead to proteins that cannot function normally. - Another type of mutation that can occur involves the gain or loss of a nucleotide in the DNA sequence.