Genetics – Major Concepts and Learning Activities[1]
Part I provides an outline of key concepts in genetics. Part II proposes an integrated sequence of learning activities to develop student understanding of these key concepts. These learning activities are aligned with the Next Generation Science Standards.[2] Part III suggests supplementary and alternative learning activities.
Part I – Key Concepts and Learning Activities
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).
Key Concepts
1. Genes in DNA à Proteins à Characteristics
· The basic way that genes influence an organism's characteristics is:
Genes in DNA provide the information necessary to make proteins, and proteins carry out many biological functions and thus influence our characteristics.
· 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).
· If a person is heterozygous (has two different alleles for a gene), often one (dominant) allele affects the phenotype and the other (recessive) allele does not. In other cases, neither allele is completely dominant or completely recessive.
· Recessive alleles often code for non-functional proteins; the dominant allele codes for enough functional protein to ensure the normal phenotype.
· A single gene may influence more than one phenotypic characteristic. Many phenotypic characteristics are influenced by more than one gene.
· An organism's characteristics are determined by the interacting effect of genes and the environment.
2. Meiosis and Fertilization à 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. Because children get their genes from their parents, they tend to resemble their parents and their siblings.
· 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.
3. Punnett Squares à 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 – Recommended Learning Activities
A. If you want to introduce all three key concepts in a single learning activity, you can use:
Genetics (Student Handout and Teacher Preparation Notes available at nmawr.edu/sci_edu/waldron/#genetics).
This activity helps students to understand basic genetics concepts, including how genotype influences phenotype and how understanding meiosis and fertilization provides the basis for understanding inheritance. The modules in the Student Handout and Genetics Supplement include (1) an introductory module that uses the example of albinism to help students understand all of the basic concepts and introduces students to the Punnett square as a summary of how genes are transmitted from parents to offspring by the processes of meiosis and fertilization, (2) a Coin Toss Genetics activity and an analysis of student data on the sex makeup of sibships, both of which help students understand the probabilistic nature of inheritance and Punnett square predictions, (3) an analysis of the inheritance of sickle cell anemia that reinforces basic concepts and introduces the important points that a single gene often has multiple phenotypic effects and alleles are often neither completely dominant nor completely recessive, and (4) pedigree analyses for recessive and dominant alleles, including challenge questions that introduce the role of new mutations and engage students in evaluating the relative advantages and disadvantages of Punnett squares and pedigrees as models of inheritance.
The Teacher Preparation Notes for this activity explain how the activity is aligned with the Next Generation Science Standards[3] (including Disciplinary Core Ideas, Scientific Practices, Crosscutting Concepts and Performance Expectations).
B. The following integrated sequence of learning activities is recommended to help students develop a solid understanding of the key concepts. The Teacher Preparation Notes for each of these activities explain how each activity is aligned with the Next Generation Science Standards.
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)
(nmawr.edu/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 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) (nmawr.edu/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) (nmawr.edu/sci_edu/waldron/#dna).
From Gene to Protein via Transcription and Translation (NGSS) (nmawr.edu/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” (nmawr.edu/sci_edu/waldron/#trans).
Mitosis – How a Single Cell Develops into the Trillions of Cells in a Human Body (NGSS)
(nmawr.edu/exchange/waldron/mitosis)
In this hands-on, minds-on activity students use model chromosomes and answer analysis and discussion questions to learn how mitosis ensures that each new cell gets a complete set of genes. Students also learn how genes on chromosomes influence phenotypic characteristics and 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)
(nmawr.edu/exchange/waldron/meiosis)
Students use model chromosomes and answer analysis and discussion questions to learn how each person inherits one copy of each gene from each of his/her parents. As they model meiosis and fertilization, students follow the alleles of three human genes from the parents' body cells through gametes to zygotes. In this way, students learn how genes are transmitted from parents to offspring through the processes of meiosis and fertilization. Students analyze the results of crossing over, independent assortment and fertilization to learn how meiosis and fertilization contribute to genetic and phenotypic variation. Students also compare and contrast mitosis and meiosis, 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)
(nmawr.edu/sci_edu/waldron/#genetics)
This activity helps students to understand basic genetics concepts, including how genotype influences phenotype and how understanding meiosis and fertilization provides the basis for understanding inheritance. The modules in the Student Handout and Genetics Supplement include (1) an introductory module that uses the example of albinism to help students understand all of the basic concepts and introduces students to the Punnett square as a summary of how genes are transmitted by the processes of meiosis and fertilization, (2) a Coin Toss Genetics activity and an analysis of student data on the sex makeup of sibships, both of which help students understand the probabilistic nature of inheritance and Punnett square predictions, (3) an analysis of the inheritance of sickle cell anemia that reinforces basic concepts and introduces the important points that a single gene often has multiple phenotypic effects and alleles are often neither completely dominant nor completely recessive, and (4) pedigree analyses for recessive and dominant alleles, including challenge questions that introduce the role of new mutations and engage students in evaluating the relative advantages and disadvantages of Punnett squares and pedigrees as models of inheritance.
Soap Opera Genetics – Genetics to Resolve Family Arguments (NGSS) (nmawr.edu/exchange/bioactivities/SoapOperaGenetics)
This analysis and discussion activity contains four "soap opera" episodes that can be used to reinforce understanding of principles of genetics and the relevance of genetics to everyday life. Concepts covered include Punnett squares, co-dominance, incomplete dominance, sex-linked inheritance, test cross, polygenic inheritance, and the interacting effects of genes and the environment on phenotypic characteristics. Each section can be used separately or with other sections, depending on your teaching goals.
Part III – Supplementary and Alternative Activities
Activities that are explicitly aligned with the Next Generation Science Standards are indicated by (NGSS).
Were the babies switched? – The genetics of Blood Types (NGSS)
(nmawr.edu/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) (nmawr.edu/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. 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)
(nmawr.edu/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)
(nmawr.edu/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) (nmawr.edu/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.