Pedigree charts use shaded symbols to show organisms that have a particular trait, such as a defective gene, being traced in the chart. a breeder wants to make a pedigree chart of male horses to avoid breeding males that have a defective gene. what symbol would the horse breeder use to show a male who is affected by a defective gene?

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.