AP BIOLOGY

Detailed explanation-1: -Mutation is the ultimate source of new alleles in plant pathogen populations. It also is the source of new alleles that create new genotypes (such as new pathotypes) within clonal lineages. Small populations have fewer alleles due to genetic drift and also because fewer mutations are generated in a small population.

Detailed explanation-2: -Mutations are changes in single nucleotides or entire chromosomes and are the sole source of new alleles.

Detailed explanation-3: -Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection. Germline mutations (that occur in eggs and sperm) can be passed on to offspring, while somatic mutations (that occur in body cells) are not passed on.

Detailed explanation-4: -Genetic variations can arise from gene variants (also called mutations) or from a normal process in which genetic material is rearranged as a cell is getting ready to divide (known as genetic recombination).