Enduring Understandings

Enduring Understandings are the College Board's AP Biology course objectives that you need to know for the AP exam. Below, you'll find those Enduring Understandings relevant to this unit. Numbering and lettering matches the course objective document linked from the main page of this website.
Every Enduring Understanding will NOT necessarily be covered during class time; you will be independently responsible for some of them.

A. Heritable information provides for continuity of life.
3. The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring.
  • a. Rules of probability can be applied to analyze passage of single gene traits from parent to offspring.
  • b. Segregation and independent assortment of chromosomes result in genetic variation.
  • c. Segregation and independent assortment can be applied to genes that are on different chromosomes.
  • d. Genes that are adjacent and close to each other on the same chromosome tend to move as a unit; the probability that they will segregate as a unit is a function of the distance between them.
  • e. The pattern of inheritance (monohybrid, dihybrid, sex-linked, and genes linked on the same homologous chromosome) can often be predicted from data that gives the parent genotype/phenotype and/or the offspring phenotypes/genotypes.
  • f. Certain human genetic disorders can be attributed to the inheritance of single gene traits or specific chromosomal changes, such as nondisjunction.
  • g. Many ethical, social and medical issues surround human genetic disorders.
4. The inheritance pattern of many traits cannot be explained by simple Mendelian genetics.
  • a. Many traits are the product of multiple genes and/or physiological processes.
  • b. Patterns of inheritance of many traits do not follow ratios predicted by Mendel's laws and can be identified by quantitative analysis, where observed phenotypic ratios statistically differ from the predicted ratios.
  • c. Some traits are determined by genes on sex chromosomes.
  • d. Some traits result from nonnuclear inheritance.
  • e. Chloroplasts and mitochondria are randomly assorted to gametes and daughter cells; thus, traits determined by chloroplast and mitochondrial DNA do not follow simple Mendelian rules.
  • f. In animals, mitochondrial DNA is transmitted by the egg and not by sperm; as such, mitochondrial-determined traits are maternally inherited.

C. The processing of genetic information is imperfect and is a source of genetic variation.
1. Changes in genotype can result in changes in phenotype.
  • a. Alterations in a DNA sequence can lead to changes in the type or amount of the protein produced and the consequent phenotype.
2. Biological systems have multiple processes that increase genetic variation.
  • c. Sexual reproduction in eukaryotes involving gamete formation, including crossing-over during meiosis and the random assortment of chromosomes during meiosis, and fertilization serve to increase variation. Reproduction processes that increase genetic variation are evolutionarily conserved and are shared by various organisms.

Textbook Reference

This is the part of your textbook that covers the material for this unit.
Ch. 11-12

Relevant Files

Here, you'll find files for this course. Copies of lecture notes will go here, as will others.


These connect to materials on other teachers' websites that you may find helpful. Generally speaking, I put links to helpful review materials - like video lectures summarizing the material - towards the top, and links to interesting extensions towards the bottom.
Human Health and the Chromosome
Investigating Genetic Disorders
Chromosome Abnormalities Gallery
National Center for Biotechnology Information (professional search databases)
Database of Human Genes
Genetics and Ethics
Gene Map of the Human Chromosome
Genomics and Its Impact on Science and Society
Genomics and Biotechnology Articles
Your Genes, Your Choices
Official Human Genome Project homepage
Heredity and Traits
Mendelian Inheritance in Humans
Mendelian Genetics
Dihybrid Crosses
Genetics Practice Problems
More Genetics Practice Problems