AP BIOLOGY

Detailed explanation-1: -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-2: -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-3: -When Replication Errors Become Mutations. Incorrectly paired nucleotides that still remain following mismatch repair become permanent mutations after the next cell division. This is because once such mistakes are established, the cell no longer recognizes them as errors.

Detailed explanation-4: -Mutations are almost permanent once you obtain them, with the only way to remove them entirely being to chug some Radaways. You can of course just expose yourself to more radiation to change your current mutation, however this just replaces one with another.

Detailed explanation-5: -There are three types of DNA Mutations: base substitutions, deletions and insertions. Single base substitutions are called point mutations, recall the point mutation Glu—–> Val which causes sickle-cell disease.