AP BIOLOGY

Detailed explanation-1: -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).

Detailed explanation-2: -A gene variant is a permanent change in the DNA sequence that makes up a gene. This type of genetic change used to be known as a gene mutation, but because changes in DNA do not always cause disease, it is thought that gene variant is a more accurate term.

Detailed explanation-3: -Although both DNA damage and DNA mutation are types of error in DNA, they are distinctly different from each other. DNA damages are physical abnormalities in DNA such as single-and double-strand breaks, while a mutation is a change in the base sequence of the DNA.

Detailed explanation-4: -Apurinic/apyrimidinic sites are common lesions in DNA and are formed either spontaneously or as intermediates during the course of the normal repair of oxidized, deaminated, or alkylated bases (1). Apurinic/apyrimidinic sites are 1 of the major types of damage generated by reactive oxygen species (ROS).

Detailed explanation-5: -(myoo-TAY-shun) Any change in the DNA sequence of a cell. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial, or have no effect.