6.7.B—Explain how changes in genotype may result in changes in phenotype

Explain how changes in genotype may result in changes in phenotype.

• Errors in DNA replication or DNA repair mechanisms as well as external factors, including radiation and reactive chemicals, can cause random mutations in the DNA.
  • i. Whether a mutation is beneficial, detrimental, or neutral depends on the environmental context.
  • ii. Mutations are a source of genetic variation.
• Errors in mitosis or meiosis can result in changes in phenotype.
  • i. Changes in chromosome number resulting from nondisjunction often result in new phenotypes caused by triploidy (aneuploidy).
  • ii. Changes in chromosome number often result in disorders with developmental limitations.
  • iii. Alterations in chromosome structure lead to genetic disorders.
  • Exclusion: Knowledge of specific disorders related to changes in chromosome number is beyond the scope of the AP Exam.