Publication No. 10784
Why Do People Look Different?
Student Laboratory Kit
Materials Included In Kit
(for 6 groups of students)
Additional Materials Required
TAE Electrophoresis buffer, concentrate 50X, 20 mL*
Preparation of 1X Electrophoresis Buffer
Note: Prepare enough buffer solution to allow each group to cover the gel in the chamber to a depth of about 2 cm. Depending on the type of electrophoresis units being used, the amount of buffer needed could be as much as 300 mL per chamber. The gel preparation requires an additional 60 mL of buffer to make a 6 x 6 cm gel.
Make fresh buffer weekly.
Be sure all connecting wires, terminals and work surfaces are dry before using the electrophoresis units. Electrical Hazard: Treat these units like any other electrical source—very carefully! Do not try to open the lid of the unit while the power is on. Wearing chemical splash goggles and gloves is strongly recommended. Wash hands thoroughly with soap and water before leaving the laboratory. Please consult current Safety Data Sheets for additional safety, handling and disposal information.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All solutions used in this lab may be disposed of down the drain using copious amounts of water according to Flinn Suggested Disposal Method #26b. Used gels may be disposed of in the regular trash according to Flinn Suggested Disposal Method #26a. The “DNA” in this kit is simulated—it does not contain any real DNA products. Each sample contains a mixture of dye solutions and sucrose, which may be disposed of by Flinn Suggested Disposal Method #26b.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering PracticesAnalyzing and interpreting data
Developing and using models
Constructing explanations and designing solutions
Disciplinary Core IdeasMS-LS1.A: Structure and Function
MS-LS3.A: Inheritance of Traits
HS-LS1.A: Structure and Function
HS-LS3.A: Inheritance of Traits
Crosscutting ConceptsStructure and function
Cause and effect
HS-LS1-1: Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells.
Answers to Prelab Questions
Father—Brown hair, blue eyes, no freckles
Both parents have a phenotype of brown hair and we see that child 2 has blond hair. This shows that both parents must have a heterozygous genotype, that is, both parents carry blond alleles although they are not expressed. Each child has a 25% probability of having a blond phenotype with heterozygous parents. This may be demonstrated using a Punnett Square.
Accept all reasonable answers that include at least a couple of terms from the background sections (e.g., genotype, phenotype, heterozygous, homozygous, genes, dominant, recessive).
Cystic fibrosis is a recessive disease, meaning two copies of the allele must be inherited for the disease to be prevalent. Every child of a heterozygous couple has a 25% chance of having the disease.
Why Do People Look Different?
Every person has a characteristic DNA fingerprint—3.2 million base pairs long, containing more than 30,000 genes. No two people, except identical twins, have the same DNA sequence. Variations in DNA fingerprints arise as DNA from two genetically different people combine during reproduction. Knowing that children inherit genes from both parents explains why children often resemble one or both of their parents due to common traits. How then can we genetically explain a child who is born with a trait neither parent has?
Each individual carries two copies of each gene called alleles. One copy is inherited from the mother and the other from the father. An individual can thus have two copies or forms of a gene that are identical, or they may have two different alleles.
In this activity simulated DNA will be analyzed using gel electrophoresis to take a deeper look into the inheritance pattern of a family’s traits. Nothing is known about the phenotypes of the “subjects” prior to running the gel. Therefore, the gel must be run properly to ensure that the correct results are obtained. The genotypes of the parents can be inferred once the phenotypes of their three children are viewed.
Agarose gel, prepared
Be sure all connecting wires, terminals and work surfaces are dry before using the electrophoresis units. Electrical Hazard: Treat these units like any other electrical source—very carefully! Do not try to open the lid of the unit while the power is on. Use heat protective gloves and eye protection when handling hot liquids. Dyes will stain skin and clothing—avoid all contact. Wear chemical splash goggles, chemical-resistant gloves and apron. Wash hands thoroughly with soap and water before leaving the laboratory.
Part A. Loading a Gel
Simulated DNA—Mother, Well 2
Part B. Running a Gel
Student Worksheet PDF