Unit: Meiosis, Mendelian Genetics & Non-Mendelian Genetics


(reorganized from the College Board AP Biology Curriculum Framework 2012 by David Knuffke)


Jump to: Meiosis; Sources of genetic variation; Mendelian Genetics; Non-Mendelian Genetics; Environment & Gene Expression; Phenotypes & Proteins; Change in Genotype leads to change in Phenotypes; Not on the national exam


Enduring understanding 3.A: Heritable information provides for continuity of life.

Essential knowledge 3.A.2: In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization.


c. Meiosis, a reduction division, followed by fertilization ensures genetic diversity in sexually reproducing organisms.

Evidence of student learning is a demonstrated understanding of each of the following:

1. Meiosis ensures that each gamete receives one complete haploid (1n) set of chromosomes.

2. During meiosis, homologous chromosomes are paired, with one homologue originating from the maternal parent and the other from the paternal parent.

3. Orientation of the chromosome pairs is random with respect to the cell poles.

4. Separation of the homologous chromosomes ensures that each gamete receives a haploid (1n) set of chromosomes composed of both maternal and paternal chromosomes.

5. During meiosis, homologous chromatids exchange genetic material via a process called “crossing over,” which increases genetic variation in the resultant gametes. [See also 3.C.2]

6. Fertilization involves the fusion of two gametes, increases genetic variation in populations by providing for new combinations of genetic information in the zygote, and restores the diploid number of chromosomes.


Learning Objectives:

LO 3.7 The student can make predictions about natural phenomena occurring during the cell cycle. [See SP 6.4]

LO 3.8 The student can describe the events that occur in the cell cycle. [See SP 1.2]

LO 3.9 The student is able to construct an explanation, using visual representations or narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis, or meiosis followed by fertilization. [See SP 6.2]

LO 3.10 The student is able to represent the connection between meiosis and increased genetic diversity necessary for evolution. [See SP 7.1]

LO 3.11 The student is able to evaluate evidence provided by data sets to support the claim that heritable information is passed from one generation to another generation through mitosis, or meiosis followed by fertilization. [See SP 5.3]



Genetic Variations:

Essential knowledge 3.C.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. [See also 1.B.1, 3.A.2, 4.C.2, 4. C3]


Learning Objectives:

LO 3.27 The student is able to compare and contrast processes by which genetic variation is produced and maintained in organisms from multiple domains. [See SP 7.2]

LO 3.28 The student is able to construct an explanation of the multiple processes that increase variation within a population. [See SP 6.2]


Enduring understanding 3.C: The processing of genetic information is imperfect and is a source of genetic variation.


Essential knowledge 3.C.1: Changes in genotype can result in changes in phenotype.

c. Errors in mitosis or meiosis can result in changes in phenotype.

Evidence of student learning is a demonstrated understanding of each of the following:

1. Changes in chromosome number often result in new phenotypes, including sterility caused by triploidy and increased vigor of other polyploids. [See also 3.A.2]

2. Changes in chromosome number often result in human disorders with developmental limitations, including Trisomy 21 (Down syndrome) and XO (Turner syndrome). [See also 3.A.2, 3.A.3]

d. Changes in genotype may affect phenotypes that are subject to natural selection. Genetic changes that enhance survival and reproduction can be selected by environmental conditions. [See also 1.A.2, 1.C.3]

To foster student understanding of this concept, instructors can choose an illustrative example such as:

Evidence of student learning is a demonstrated understanding of the following:

  1. Selection results in evolutionary change.


Learning Objectives:

LO 3.24 The student is able to predict how a change in genotype, when expressed as a phenotype, provides a variation that can be subject to natural selection. [See SP 6.4, 7.2]

LO 3.25 The student can create a visual representation to illustrate how changes in a DNA nucleotide sequence can result in a change in the polypeptide produced. [See SP 1.1]

LO 3.26 The student is able to explain the connection between genetic variations in organisms and phenotypic variations in populations. [See SP 7.2]


Mendelian Principles and Genetics:

Essential knowledge 3.A.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.

Evidence of student learning is a demonstrated understanding of each of the following:

1. Segregation and independent assortment can be applied to genes that are on different chromosomes.

2. 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.

3. 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.

c. Certain human genetic disorders can be attributed to the inheritance of single gene traits or specific chromosomal changes, such as nondisjunction.

To foster student understanding of this concept, instructors can choose an illustrative example such as:

d. Many ethical, social and medical issues surround human genetic disorders.

To foster student understanding of this concept, instructors can choose an illustrative example such as:


Learning Objectives:

LO 3.12 The student is able to construct a representation that connects the process of meiosis to the passage of traits from parent to offspring. [See SP 1.1, 7.2]

LO 3.13 The student is able to pose questions about ethical, social or medical issues surrounding human genetic disorders. [See SP 3.1]

LO 3.14 The student is able to apply mathematical routines to determine Mendelian patterns of inheritance provided by data sets. [See SP 2.2]


Non-Mendelian Genetics:

Essential knowledge 3.A.4: The inheritance pattern of many traits cannot be explained by simple Mendelian genetics.

  1. Many traits are the product of multiple genes and/or physiological processes.

Evidence of student learning is a demonstrated understanding of the following:

1. 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.

b. Some traits are determined by genes on sex chromosomes.

To foster student understanding of this concept, instructors can choose an illustrative example such as:

c. Some traits result from nonnuclear inheritance.

Evidence of student learning is a demonstrated understanding of each of the following:

1. 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.

2. In animals, mitochondrial DNA is transmitted by the egg and not by sperm; as such, mitochondrial-determined traits are maternally inherited.


Learning Objectives:

LO 3.15 The student is able to explain deviations from Mendel’s model of the inheritance of traits. [See SP 6.2, 6.5]

LO 3.16 The student is able to explain how the inheritance patterns of many traits cannot be accounted for by Mendelian genetics. [See SP 6.3]

LO 3.17 The student is able to describe representations of an appropriate example of inheritance patterns that cannot be explained by Mendel’s model of the inheritance of traits. [See SP 1.2]



Enduring understanding 4.C: Naturally occurring diversity among and between components within biological systems affects interactions with the environment.


Essential knowledge 4.C.1: Variation in molecular units provides cells with a wider range of functions.

b. Multiple copies of alleles or genes (gene duplication) may provide new phenotypes. [See also 3.A.4, 3.C.1]

Evidence of student learning is a demonstrated understanding of each of the following:

1. A heterozygote may be a more advantageous genotype than a homozygote under particular conditions, since with two different alleles, the organism has two forms of proteins that may provide functional resilience in response to environmental stresses.

2. Gene duplication creates a situation in which one copy of the gene maintains its original function, while the duplicate may evolve a new function.

To foster student understanding of this concept, instructors can choose an illustrative example such as:

The antifreeze gene in fish


Learning Objective:

LO 4.22 The student is able to construct explanations based on evidence of how variation in molecular units provides cells with a wider range of functions. [See SP 6.2]


Effect of Environment on Gene Expression:

Essential knowledge 4.C.2: Environmental factors influence the expression of the genotype in an organism.

a. Environmental factors influence many traits both directly and indirectly. [See also 3.B.2, 3.C.1]

To foster student understanding of this concept, instructors can choose an illustrative example such as:

b. An organism’s adaptation to the local environment reflects a flexible response of its genome.

To foster student understanding of this concept, instructors can choose an illustrative example such as:


Learning Objectives:

LO 4.23 The student is able to construct explanations of the influence of environmental factors on the phenotype of an organism. [See SP 6.2]

LO 4.24 The student is able to predict the effects of a change in an environmental factor on the genotypic expression of the phenotype gene expression and resulting phenotype of an organism. [See SP 6.4]


Untested: not on the College Board national AP Biology exam

The details of sexual reproduction cycles in various plants and animals are beyond the scope of the course and the AP Exam. However, the similarities of the processes that provide for genetic variation are relevant and should be the focus of instruction.



Unit: Molecular Genetics


Enduring understanding 3.A: Heritable information provides for continuity of life.


Essential knowledge 3.A.1: DNA, and in some cases RNA, is the primary source of heritable information.

(phenotypes and proteins)

d. Phenotypes are determined through protein activities.

To foster student understanding of this concept, instructors can choose an illustrative example such as:


Learning Objectives:

LO 3.3 The student is able to describe representations and models that illustrate how genetic information is copied for transmission between generations. [See SP 1.2]

LO 3.4 The student is able to describe representations and models illustrating how genetic information is translated into polypeptides. [See SP 1.2]

LO 3.5 The student can justify the claim that humans can manipulate heritable information by identifying at least two commonly used technologies. [See SP 6.4]

LO 3.6 The student can predict how a change in a specific DNA or RNA sequence can result in changes in gene expression. [See SP 6.4]



Enduring understanding 3.C: The processing of genetic information is imperfect and is a source of genetic variation.


Essential knowledge 3.C.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. [See also 3.A.1]

Evidence of student learning is a demonstrated understanding of the following:

1. DNA mutations can be positive, negative or neutral based on the effect or the lack of effect they have on the resulting nucleic acid or protein and the phenotypes that are conferred by the protein.

b. Errors in DNA replication or DNA repair mechanisms, and external factors, including radiation and reactive chemicals, can cause random changes, e.g., mutations in the DNA.

Evidence of student learning is a demonstrated understanding of the following:

1. Whether or not a mutation is detrimental, beneficial or neutral depends on the environmental context. Mutations are the primary source of genetic variation.

d. Changes in genotype may affect phenotypes that are subject to natural selection. Genetic changes that enhance survival and reproduction can be selected by environmental conditions. [See also 1.A.2, 1.C.3]

To foster student understanding of this concept, instructors can choose an illustrative example such as:

Evidence of student learning is a demonstrated understanding of the following:

  1. Selection results in evolutionary change.


Learning Objectives:

LO 3.24 The student is able to predict how a change in genotype, when expressed as a phenotype, provides a variation that can be subject to natural selection. [See SP 6.4, 7.2]

LO 3.25 The student can create a visual representation to illustrate how changes in a DNA nucleotide sequence can result in a change in the polypeptide produced. [See SP 1.1]

LO 3.26 The student is able to explain the connection between genetic variations in organisms and phenotypic variations in populations. [See SP 7.2]


Essential knowledge 3.C.2: Biological systems have multiple processes that increase genetic variation.

a. The imperfect nature of DNA replication and repair increases variation.

b. The horizontal acquisitions of genetic information primarily in prokaryotes via transformation (uptake of naked DNA), transduction (viral transmission of genetic information), conjugation (cell-to-cell transfer) and transposition (movement of DNA segments within and between DNA molecules) increase variation. [See also 1.B.3]


Learning Objectives:

LO 3.27 The student is able to compare and contrast processes by which genetic variation is produced and maintained in organisms from multiple domains. [See SP 7.2]

LO 3.28 The student is able to construct an explanation of the multiple processes that increase variation within a population. [See SP 6.2]


Essential knowledge 3.C.3: Viral replication results in genetic variation, and viral infection can introduce genetic variation into the hosts.

a. Viral replication differs from other reproductive strategies and generates genetic variation via various mechanisms. [See also 1.B.3]

Evidence of student learning is a demonstrated understanding of each of the following:

1. Viruses have highly efficient replicative capabilities that allow for rapid evolution and acquisition of new phenotypes.

2. Viruses replicate via a component assembly model allowing one virus to produce many progeny simultaneously via the lytic cycle.

3. Virus replication allows for mutations to occur through usual host pathways.

4. RNA viruses lack replication error-checking mechanisms, and thus have higher rates of mutation.

5. Related viruses can combine/recombine information if they infect the same host cell.

6. HIV is a well-studied system where the rapid evolution of a virus within the host contributes to the pathogenicity of viral infection.

b. The reproductive cycles of viruses facilitate transfer of genetic information.

Evidence of student learning is a demonstrated understanding of each of the following:

1. Viruses transmit DNA or RNA when they infect a host cell. [See also 1.B.3]

To foster student understanding of this concept, instructors can choose an

illustrative example such as:


2. Some viruses are able to integrate into the host DNA and establish a latent (lysogenic) infection. These latent viral genomes can result in new properties for the host such as increased pathogenicity in bacteria.


Learning Objectives:

LO 3.29 The student is able to construct an explanation of how viruses introduce

genetic variation in host organisms. [See SP 6.2]

LO 3.30 The student is able to use representations and appropriate models to

describe how viral replication introduces genetic variation in the viral population.

[See SP 1.4]


Enduring understanding 4.A: Interactions within biological systems lead to complex properties.


Essential knowledge 4.A.3: Interactions between external stimuli and regulated gene expression result in specialization of cells, tissues and organs.

a. Differentiation in development is due to external and internal cues that trigger gene regulation by proteins that bind to DNA. [See also 3.B.1, 3. B.2]

b. Structural and functional divergence of cells in development is due to expression of genes specific to a particular tissue or organ type. [See also 3.B.1, 3.B.2]

c. Environmental stimuli can affect gene expression in a mature cell. [See also 3.B.1, 3.B.2]


Learning Objective:

LO 4.7 The student is able to refine representations to illustrate how interactions between external stimuli and gene expression result in specialization of cells, tissues and organs. [See SP 1.3]


Enduring understanding 4.C: Naturally occurring diversity among and between components within biological systems affects interactions with the environment.


Essential knowledge 4.C.1: Variation in molecular units provides cells with a wider range of functions.

a. Variations within molecular classes provide cells and organisms with a wider range of functions. [See also 2.B.1, 3.A.1, 4.A.1, 4.A.2]

To foster student understanding of this concept, instructors can choose an illustrative example such as:


Learning Objective:

LO 4.22 The student is able to construct explanations based on evidence of how variation in molecular units provides cells with a wider range of functions. [See SP 6.2]