Grades 7-10

Genetics, human diseases, cell biology, physiology

Teacher Resources

Mystery of the Crooked Cell is an activity modified by Learning Undefeated to help students explore genetic diseases and tracing genetics through the use of Punnett squares and gel electrophoresis.

Sickle cell anemia is a hereditary disease that is passed down to an individual from their parents. The disease causes red blood cells to form into an abnormal crescent shape, which prevents the cells from efficiently carrying oxygen to the body’s tissues.

Learning Objectives

Students will be able to

  • Illustrate how amino acids interact to create a protein
  • Identify an enzyme’s specific substrate
  • Recognize the symptoms of sickle cell anemia and hemoglobin’s role in the disease
  • Differentiate between a patient with sickle cell anemia and a patient without sickle cell anemia using gel electrophoresis
  • Calculate the probability of an offspring having a specific phenotype using a Punnett square
  • Analyze a pedigree to track a gene through a family
  • Show how a point mutation can change the function of a protein
Standards Alignments + Connections

Next Generation Science Standards Connections

MS-LS3-1: Develop and use a model to describe why structural changes to genes (mutations) located on chromosomes may affect proteins and may result in harmful, beneficial, or neutral effects to the structure and function of the organism.

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.

HS-LS3-3: Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population.

Texas Essential Knowledge and Skills for Science Connections

7.13D: Describe and give examples of how natural and artificial selection change the occurrence of traits in a population over generations.

8.13B: Describe the function of genes within chromosomes in determining inherited traits of offspring;

8.13C: Describe how variations of traits within a population lead to structural, behavioral, and physiological adaptations that influence the likelihood of survival and reproductive success of a species over generations.

BIOL.7A: Identify components of DNA, explain how the nucleotide sequence specifies some traits of an organism, and examine scientific explanations for the origin of DNA

BIOL.7B: Describe the significance of gene expression and explain the process of protein synthesis using models of DNA and ribonucleic acid (RNA)

BIOL.7C: Identify and illustrate changes in DNA and evaluate the significance of these changes;

BIOL.7D: Discuss the importance of molecular technologies such as polymerase chain reaction (PCR), gel electrophoresis, and genetic engineering that are applicable in current research and engineering practices.

BIOL.8B: predict possible outcomes of various genetic combinations using monohybrid and dihybrid crosses, including non-Mendelian traits of incomplete dominance, codominance, sex-linked traits, and multiple alleles

Activities to Gather Evidence

Background Information

The crescent, or sickle, shape is due to a mutation in the gene that codes for a protein in red blood cells which binds to oxygen. The mutation codes for a specific amino acid that results in a mutated hemoglobin protein called valine, which is hydrophobic. This hydrophobia causes the sickle shape of the red blood cell.

Normal Hemoglobin: This phenotype occurs when an individual has two wild alleles (in this lab, we represent this genotype as NN).

Sickle Hemoglobin: This phenotype only occurs when an individual receives two mutated alleles (represented as SS).

Carrier: An individual who receives one normal and one sickle allele from their parents is a carrier for sickle cell anemia (genotype represented as NS). A carrier may go into “sickle cell crisis,” experiencing the symptoms of sickle cell under severe circumstances. However, a sickle cell carrier is also more resistant to the infectious disease malaria.

Pre-Laboratory Engagement

Pre-Lab Questions:

  • What causes sickle cell anemia and how is it passed through genetics?
  • What is the difference between being heterozygous for a gene and homozygous for a gene?
  • What is the difference between a genotype and a phenotype?

Click here for the Pre-lab Classroom Activity for a group activity investigating patient history, manipulating models of alleles, and gathering evidence to aid in discussion of sickle cell anemia.

Laboratory Activity

A local high school football player was rushed to the hospital after collapsing on the field. The player reported to the emergency room physician, Dr. James Herrick, that he had experienced similar symptoms multiple times during his childhood. These symptoms include extreme fatigue after non-strenuous exercise, being unusually short of breath, extreme pain in his joints and muscles, a yellowish tint in the whites of his eyes, and tenderness in his abdomen. Consequently, the patient would often have to spend time in bed after a “crisis”.

A look at his immediate family history reveals that neither of his parents have had similar symptoms. However, upon further investigation, it is revealed that the patient’s paternal uncle and grandmother shared the same symptoms under the same circumstances. Based on this medical history, Dr. Herrick believes the patient may have sickle cell anemia.

Dr. Herrick has asked for your help in confirming his diagnosis. To do so, you will be testing the patient’s hemoglobin protein using gel electrophoresis. Based on your results, you can then confirm the patient’s diagnosis.

Post-Laboratory Extension

Click here to see our Post-Lab Classroom Activity, with discussion prompts and real-world applications to the sickle cell lab.

Additional Resources

For useful information regarding this lab, follow these links:

Other useful links:

What is a gene?

Proteins are the Body’s Workers
Look into amino acids, the building blocks of proteins.

Sickle Cell Explained
Explanation of sickle cell disease.

Center for Disease Control
One stop shop for information from the CDC on Sickle Cell Disease.

CDC Resource for family history

A Brief History of Hemoglobin
Look into amino acids, the building blocks of proteins.

Inheriting Genetic Conditions
Frequently asked questions on how diseases can travel through families.

Point Mutations
NIH definition of point mutations.

Career Snapshot
Helathcare Industry (DallasQuickgrabs)

DNA Learning Center
3-D animation of the sickle cell mutation.

Gel Electrophoresis Tools
Run a virtual gel electrophoresis.

3-D Model’s of the hemoglobin protein with options to show specific features of each side chain.