Genetics – Major Concepts, Common Misconceptions, and Learning Activities1
Part I provides an outline of key concepts in genetics. Part II presents common misconceptions. Part III
recommends an integrated sequence of learning activities to develop student understanding of the key
concepts and counteract common misconceptions.2 Part IV suggests supplementary learning activities.
Part I – Key Concepts
Key Concepts from the Next Generation Science Standards (NGSS)3
 Students will gain understanding of several Disciplinary Core Ideas:
o
LS1.A: Structure and Function – "All cells contain genetic information in the form of DNA
molecules. Genes are regions in the DNA that contain the instructions that code for the
formation of proteins."
o
LS1.B: Growth and Development of Organisms – "In multicellular organisms individual cells
grow and then divide by a process called mitosis, thereby allowing the organism to grow. The
organism begins as a single cell (fertilized egg) that divides successively to produce many cells,
with each parent cell passing identical genetic material (two variants of each chromosome pair)
to both daughter cells. Cellular division and differentiation produce and maintain a complex
organism, composed of systems of tissues and organs that work together to meet the needs of
the whole organism."
o
LS3.A: Inheritance of Traits – "Each chromosome consists of a single very long DNA
molecule, and each gene on the chromosome is a particular segment of that DNA. The
instructions for forming species' characteristics are carried in DNA."
o
LS3.B: Variation of Traits – “In sexual reproduction, meiosis can create new genetic
combinations and thus more genetic variation. Although DNA replication is highly regulated
and remarkably accurate, errors do occur and result in mutations, which are also a source of
genetic variation.”
For additional information about NGSS Performance Expectations, Crosscutting Concepts, and
Science and Engineering Practices and how the recommended learning activities support these learning
goals, see the Teacher Preparation Notes for each recommended learning activity and the summary
tables at http://serendipstudio.org/exchange/bioactivities/NGSS.
More Specific Key Concepts
Genetics is primarily concerned with two questions:
 How do our genes influence our characteristics?
 How are genes transmitted from parents to offspring?
This overview and the suggested learning activities will show how:
 understanding the functions of DNA and proteins provides the basis for understanding how
genes influence an organism's characteristics (Key Concept 1 below)
 understanding meiosis and fertilization provides the basis for understanding how genes are
transmitted from parents to offspring (Key Concepts 2 and 3 below).
1
By Dr. Ingrid Waldron, Department of Biology, University of Pennsylvania, 2019. These Teacher Notes are available at
http://serendipstudio.org/exchange/bioactivities/GeneticsConcepts .
2
3
These learning activities are aligned with the Next Generation Science Standards, http://www.nextgenscience.org/
http://www.nextgenscience.org/sites/default/files/HS%20LS%20topics%20combined%206.13.13.pdf and
http://www.nextgenscience.org/sites/default/files/Appendix%20G%20%20Crosscutting%20Concepts%20FINAL%20edited%204.10.13.pdf
1. Genes in DNA  Proteins  Characteristics
 Genes in DNA provide the information necessary to make proteins, and proteins carry out many
biological functions and thus influence our characteristics.
 More specifically:
nucleotide sequence in the DNA of a gene
 nucleotide sequence in messenger RNA (mRNA)
transcription
 amino acid sequence in a protein
translation
 structure and function of the protein
(e.g. normal hemoglobin vs. sickle cell hemoglobin)
 person's characteristics or traits
(e.g. normal health vs. sickle cell anemia)4





Different alleles (different versions of the same gene) code for different versions of a protein which
can result in differences in phenotype (an organism's appearance or other observable
characteristics). Differences in phenotype can also result from differences in gene expression and
effects of the environment.
A person is homozygous for a gene if both alleles for that gene are the same. A person is
heterozygous if they have two different alleles for the gene.
For some pairs of alleles, the phenotype of a heterozygous individual is the same as the phenotype
of one of the two types of homozygous individual. The allele that results in the same phenotype for
both a heterozygous individual and a homozygous individual is dominant. The other allele is
recessive.
In other cases, neither allele is completely dominant or completely recessive. In incomplete
dominance, the phenotype of a heterozygous individual is halfway between the phenotypes of the
two homozygous individuals. In codominance, both alleles affect the phenotype of the
heterozygous individual.
A single gene may influence more than one phenotypic characteristic. Many phenotypic
characteristics are influenced by more than one gene.
2. Meiosis and Fertilization  Inheritance
 The behavior of chromosomes during meiosis and fertilization provides the basis for understanding
the inheritance of genes.
 As a result of meiosis, each egg receives one copy of each gene from the mother and each sperm
receives one copy of each gene from the father. When the gametes unite in fertilization, the zygote
that develops into the child receives one copy of each gene from the mother and another copy of
each gene from the father. Repeated mitosis ensures that each cell in a child’s body has the same
genes as the zygote. Because children get their genes from their parents, they tend to resemble their
parents and their siblings. (Environmental influences also contribute to the similarity of parents and
offspring.)
 However, meiosis results in genetically diverse sperm and eggs which, together with random
fertilization, results in genetic diversity of the zygotes/children produced by the same mother and
father. This can result in phenotypic diversity.
4
For information about the processes of transcription and translation, see pages 2-3 of
http://serendipstudio.org/exchange/files/TranscriptionTranslationTN.pdf.
2
3. Punnett Squares  Probabilistic Predictions of Inheritance
 The processes of meiosis and fertilization can be summarized in Punnett squares which can be used
to predict the genotypes and phenotypes of offspring.
 Quantitative predictions from Punnett squares are accurate for large samples, but random variation
in the genetic makeup of the sperm and egg that unite to form each zygote often results in
substantial discrepancies between the Punnett square predictions and the outcomes observed in
small samples such as individual families.
 Each fertilization event is independent of other fertilization events, so the genetic makeup of each
child is independent of the genetic makeup of any siblings.
Part II – Common Misconceptions5
Sometimes our teaching may inadvertently reinforce some of these misconceptions (especially b-e).
The learning activities proposed in Part III are designed to counteract these misconceptions.
a. Students often do not understand the distinctions between a chromosome, a gene and an allele.
Similarly, students often do not understand the difference between a chromatid and a chromosome.
b. Each trait is influenced by a single gene, and each gene influences only one trait (not recognizing
how common polygenic traits and pleiotropy are).
c. There are only two alleles for each gene.
d. Genes are the sole determinants of traits (not recognizing environmental influences).
e. Dominant traits are the most common traits (which is true for some genes, but not all).
f. A person who doesn’t have a characteristic lacks the gene for this characteristic (not recognizing
that the person has other alleles for this gene).
g. All genetic conditions are inherited (not recognizing the important role of new mutations or
mistakes in meiosis in causing some genetic conditions).
h. All mutations are harmful (which is often true, but not always).
i. Students often fail to recognize the probabilistic nature of Punnett square predictions and
inheritance.
Part III – Recommended Learning Activities
The following integrated sequence of learning activities is recommended to help students develop a
solid understanding of the key concepts. These learning activities will also help to counteract common
misconceptions. The Teacher Preparation Notes for each of these activities explain how each activity is
aligned with the Next Generation Science Standards (NGSS).
This integrated sequence of learning activities begins with three activities to help students understand
DNA structure and replication and the basic molecular biology of how genes influence characteristics.
Some teachers may prefer to use only the first of these activities before beginning the discussion of
mitosis, meiosis and fertilization and inheritance and then return to other aspects of basic molecular
biology after completing the discussion of transmission genetics.
Understanding the Functions of Proteins and DNA (NGSS)
(http://serendipstudio.org/exchange/bioactivities/proteins )
This overview provides a sequence of learning activities to help students understand that proteins and
DNA are not just abstract concepts in biology textbooks, but rather crucial components of our bodies
that affect functions and characteristics that students are familiar with. Students learn about how
proteins contribute to the digestion of food and to characteristics such as albinism, sickle cell anemia
5
These misconceptions are taken primarily from http://knowgenetics.org/common_misconceptions/ and
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2278104/ (especially tables 5 and 6).
3
and hemophilia. Then, students learn about the relationship between the genetic information in DNA
and the different versions of these proteins. The discussion, web-based, and hands-on learning
activities presented are appropriate for an introductory unit on biological molecules or as an
introduction to a unit on molecular biology.
DNA Structure, Function and Replication (NGSS)
(http://serendipstudio.org/exchange/bioactivities/DNA)
This analysis and discussion activity can be used to introduce your students to key concepts about
DNA structure, function and replication or to review these topics. This activity includes hands-on
modeling of DNA replication. If you prefer a hands-on activity in which students extract DNA, see
“DNA” (NGSS) (http://serendipstudio.org/sci_edu/waldron/#dna).
From Gene to Protein via Transcription and Translation (NGSS)
(http://serendipstudio.org/exchange/bioactivities/trans)
In this analysis and discussion activity, students learn (1) how genes influence characteristics such as
albinism and sickle cell anemia and (2) how genes provide the instructions for making a protein via
transcription and translation. To help students understand the processes of transcription and translation,
this activity includes multiple figures, brief explanations, and questions, together with four
recommended videos. This activity can be used to introduce students to transcription and translation or
to reinforce and enhance student understanding. If you prefer a hands-on activity that uses simple
paper models to simulate the molecular processes of transcription and translation, see “From Gene to
Protein – Transcription and Translation” (http://serendipstudio.org/sci_edu/waldron/#trans).
Mitosis and the Cell Cycle – How a Single Cell Develops into the Trillions of Cells in a Human
Body (NGSS)
(http://serendipstudio.org/exchange/waldron/mitosis)
In this hands-on, minds-on activity students use model chromosomes and answer analysis and
discussion questions to learn how the cell cycle produces genetically identical daughter cells. Students
learn how DNA replication and mitosis ensure that each new cell gets a complete set of chromosomes
with a complete set of genes. Students learn why each cell needs a complete set of genes and how
genes influence phenotypic characteristics. Finally, students analyze exponential growth to understand
how a single cell develops into the trillions of cells in a human body. This activity can be used as an
introduction to mitosis or to reinforce understanding of mitosis.
Meiosis and Fertilization – Understanding How Genes Are Inherited (NGSS)
(http://serendipstudio.org/exchange/waldron/meiosis)
In this hands-on, minds-on activity, students use model chromosomes and answer analysis and
discussion questions to learn about the processes of meiosis and fertilization. As they model meiosis
and fertilization, students follow the alleles of a human gene from the parents' body cells through
gametes to zygotes; thus, students learn how a person inherits one copy of each gene from each of
his/her parents. To learn how meiosis contributes to genetic variation, students analyze the results of
crossing over and independent assortment. Students also compare and contrast meiosis and mitosis,
and they learn how a mistake in meiosis can result in Down syndrome or death of an embryo. This
activity can be used to introduce meiosis and fertilization or to review these processes.
Genetics (NGSS)
(http://serendipstudio.org/sci_edu/waldron/#genetics)
The Genetics Student Handout begins with sections that help students to understand basic principles of
genetics, including (1) how genotype influences phenotype via the effects of genes on protein structure
and function and (2) how genes are transmitted from parents to offspring through the processes of
4
meiosis and fertilization. Then, a coin flip activity models the probabilistic nature of inheritance and
Punnett square predictions. Additional concepts covered include polygenic inheritance, incomplete
dominance, and how a new mutation can result in a genetic condition that was not inherited. The
Genetics Supplement Student Handout includes (1) an alternative version of the introduction to genetic
principles that does not require prior completion of our meiosis and fertilization activity; (2) an
analysis of the genetics of sex determination that helps students understand the probabilistic nature of
inheritance; and (3) analyses of the molecular basis of sickle cell anemia and sickle cell trait, including
the multiple phenotypic effects of a single gene, plus a pedigree analysis.
Part IV – Supplementary Activities6
Cell Differentiation and Epigenetics (NGSS)
(http://serendipstudio.org/exchange/bioactivities/epigenetics)
In this analysis and discussion activity, students answer minds-on questions as they learn about the
differentiation of specialized cell types, including the role of changes in epigenetic control of gene
expression during cell differentiation. Students also learn about environmental influences on epigenetic
control of gene expression and the need for cell division and differentiation even in a fully grown
adult.
Soap Opera Genetics – Genetics to Resolve Family Arguments (NGSS)
(http://serendipstudio.org/exchange/bioactivities/SoapOperaGenetics)
This analysis and discussion activity contains three "soap opera" episodes that contribute to student
understanding of the principles of inheritance and the relevance of genetics to everyday life. In the first
episode, students explain the relevant biology to answer the probing questions of a skeptical father who
wants to know how his baby could be albino when neither he nor his wife are albino. The second
episode, "Were the babies switched?" covers the concepts of co-dominance, incomplete dominance,
polygenic inheritance, and the combined effects of genes and the environment on phenotypic
characteristics. In the third episode, students analyze sex-linked inheritance. Each episode can be used
separately or with other episodes, depending on your teaching goals.
Were the babies switched? – The Genetics of Blood Types (NGSS)
(http://serendipstudio.org/sci_edu/waldron/#blood)
In this minds-on, hands-on activity, students learn the genetics of the ABO blood type system. Students
use simple chemicals to simulate blood type tests and then carry out genetic analyses to determine
whether hospital staff accidentally switched two babies born on the same day. This activity reinforces
student understanding of the fundamental concepts that genes code for proteins which influence an
organism's characteristics and Punnett squares summarize how meiosis and fertilization result in
inheritance. Students also learn about codominance and multiple alleles of a single gene. The first
version of the Student Handout includes an introduction to the immunobiology of the ABO blood type
system. The second version includes an analysis of the genetics of skin color in which students learn
how fraternal twins could have very different skin colors, the concept of incomplete dominance, and
how a single phenotypic characteristic can be influenced by multiple genes and the environment.
The Molecular Biology of Mutations and Muscular Dystrophy (NGSS)
(http://serendipstudio.org/exchange/bioactivities/mutation)
In this analysis and discussion activity, students review basic molecular biology and learn how to use a
codon wheel. Then, they analyze the molecular effects of different types of point mutations and
deletion mutations and the reasons why deletion mutations generally have more severe effects.
6
Activities that are explicitly aligned with the Next Generation Science Standards are indicated by (NGSS).
5
Students use this background to analyze the different types of deletion mutations that cause the more
severe Duchenne muscular dystrophy vs. the milder Becker muscular dystrophy.
Genetic Engineering Challenge – How can scientists develop a type of rice that could prevent
vitamin A deficiency? (NGSS)
(http://serendipstudio.org/exchange/bioactivities/geneticengineer)
This analysis and discussion activity begins with an introduction to vitamin A deficiency, rice seeds,
and genetic engineering. Next, several questions challenge students to design a basic plan that could
produce a genetically engineered rice plant that makes rice grains that contain pro-vitamin A.
Subsequent information and questions guide students in developing an understanding of the basic
techniques of genetic engineering. Students use fundamental molecular biology concepts as they think
about how to solve a practical problem. This activity can be used to introduce students to genetic
engineering or to reinforce basic understanding of genetic engineering.
UV, Mutations, and DNA Repair (NGSS)
(http://serendipstudio.org/sci_edu/waldron/#uvmutations)
Students learn about the effects of UV light, mutations and DNA repair on the survival of prokaryotes
and the risk of skin cancer. In the first experiment, students evaluate the effects of different durations
of UV exposure on survival and population growth of Haloferax volcanii. This experiment also tests
for photorepair of DNA damage. Students design the second experiment, which evaluates the
effectiveness of sunscreen. In addition, students answer analysis and discussion questions that promote
their understanding of molecular biology, cancer, and the interpretation of experimental results.
Molecular Biology: Major Concepts and Learning Activities (NGSS)
(http://serendipstudio.org/exchange/bioactivities/MolBio)
This overview reviews key concepts and learning activities to help students understand how genes
influence our traits by molecular processes. Topics covered include basic understanding of the
important role of proteins and DNA; DNA structure, function and replication; the molecular biology of
how genes influence traits, including transcription and translation; and the molecular biology of
mutations. To help students understand the relevance of these molecular processes, the suggested
learning activities link alleles of specific genes to human characteristics such as albinism, sickle cell
anemia and muscular dystrophy. Suggested activities include hands-on laboratory and simulation
activities, Web-based simulations, discussion activities and a vocabulary review game.
DNA from the Beginning – An Animated Primer of 75 Experiments That Made Modern Genetics
(http://www.dnaftb.org/)
This online resource includes sections on classical genetics, molecules of genetics, and genetic
organization and control. These provide an excellent introduction to a broader range of genetics
concepts. Each concept and the related research evidence are explained with an animation, a video, and
an engaging online problem.
Several computer simulations can be used to help students learn and understand basic concepts of
genetics. In Virtual Genetics Lab (available at http://vgl.umb.edu/) students develop explanatory
models of genetic phenomena and test them. Biologica Web Labs include Dragon Genetics where
students investigate the relationship between genotype and phenotype and Mendel's Peas where
students learn the basic principles of meiosis, fertilization and inheritance (available at
http://biologica.concord.org/webtest1/web_labs.htm ).
6
Cootie Genetics
(available at http://biotech.bio5.org/cooties, with a helpful overview in The American Biology Teacher
76 (3): 189-193, 2014)
In this hands-on, inquiry-based activity students investigate how traits are inherited. This activity is
suggested as an introduction before learning the Mendelian laws of inheritance.
Dragon Genetics – Understanding Inheritance (http://serendipstudio.org/sci_edu/waldron/#dragon2)
In this simulation activity students mimic the processes of meiosis and fertilization to investigate the
inheritance of multiple genes and then use their understanding of concepts such as dominant/recessive
alleles, incomplete dominance, sex-linked inheritance, and epistasis to interpret the results of the
simulation. This activity can be used as a culminating activity after you have introduced classical
genetics, or it can serve as a formative assessment to identify any areas of confusion that require
additional clarification.
Should states repeal their laws banning first cousin marriages? -- Effects of first cousin marriage
on health risks for their children
(http://serendipstudio.org/exchange/bioactivities/GeneticsFirstCousins)
This minds-on discussion/worksheet activity challenges students to analyze which types of genetic
conditions will be more common among children of first cousin marriage and to use evidence
concerning the magnitude of observed health effects to evaluate whether laws banning first cousin
marriage in 25 states should be repealed.
Genetics Jeopardy Review Game
(http://serendipstudio.org/exchange/bioactivities/GeneticsJeopardy)
7