Which phenotypic change is genetic? a. plants in a field are smaller than usual after a drought. b. the flower color in a population changes over time. c. a person with fair skin gets severely sunburned. d. an individual cuts his hair and changes its color.

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).