AP BIOLOGY

Detailed explanation-1: -A mutation is a change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection.

Detailed explanation-2: -Gene variants (also known as mutations) can have varying effects on health, depending on where they occur and whether they alter the function of essential proteins. Variant types include the following: Substitution. This type of variant replaces one DNA building block (nucleotide) with another.

Detailed explanation-3: -While mutations always change the DNA sequence, they do not always cause a change in the resulting protein or an obvious effect on the organism. This can occur because most amino acids can be coded by two or more different codons.

Detailed explanation-4: -Mutations are changes that occur in DNA or RNA. Mutations can be silent, meaning they have no effect on the protein made, due to redundancy in the genetic code.

Detailed explanation-5: -Mutations result either from errors in DNA replication or from the damaging effects of mutagens, such as chemicals and radiation, which react with DNA and change the structures of individual nucleotides. All cells possess DNA-repair enzymes that attempt to minimize the number of mutations that occur (Section 14.2).