In this lesson, students explore how DNA fits into chromosomes and how chromosomes relate to the human body. They learn about DNA replication and protein synthesis and model these two processes in Web activities. Then they read about molecular genetics and discuss the significance of proteins in the human body. Finally, they learn how mutations may affect protein synthesis and cause genetic disorders.
- Understand the structure of DNA and the process of DNA replication
- Describe the process of protein synthesis
- Recognize the importance of proteins in the human body
- Understand how mutations affect protein synthesis and how they can cause genetic disorders
- Two to three class periods
- Journey into DNA Flash Interactive
- DNA Workshop Shockwave Interactive
- How DNA Replicates QuickTime Video
- From DNA to Protein QuickTime Video
- Molecular Level of Genetics PDF Document
- A Mutation Story QuickTime Video
- Copies of theMolecular Level of Genetics article
Before the Lesson
- Make copies of theMolecular Level of Genetics article.
After the Lesson
- Relate the process of DNA replication to mitosis.
- Do the Inheritance of Genetic Disorders lesson.
- Do the The Human Genome Project lesson.
1. Have students explore the Journey into DNA Web activity. Then have them make a series of drawings that "zoom in" to show how DNA fits into chromosomes and how chromosomes relate to cells in the human intestine.
2. Show the How DNA Replicates video. Then have students do the "DNA Replication" section of theDNA Workshop Web activity. Tell students to click on "DNA Replication" at the top left corner. After students have completed this activity, discuss the following:
- What is the structure of a DNA molecule? What are the building blocks of DNA?
- Which DNA bases pair with each other? What part of the DNA molecule do they form?
- How does DNA replicate and why?
- What is a mutation, and how might it occur during replication?
3. Show the From DNA to Protein video. Then have students do the "Protein Synthesis" section of theDNA Workshop Web activity. Tell students to click on "Protein Synthesis" at the top right corner. When they have completed this activity, ask them to write a paragraph, with illustrations, describing the steps of the protein synthesis process from DNA to polypeptide chain. Ask them to incorporate the following terms into their description:
- DNA, bases, transcription, mRNA, translation, codons, anticodons, ribosomes, polypeptides, amino acids
As an option, you might have students make a flipbook or create a model to show the process of protein synthesis.
4. Next, have students read the Molecular Level of Genetics article. Ask students to compare their descriptions of protein synthesis from step 3 above to the description in the tutorial. Then discuss the following:
- Why are protein molecules essential to the human body? What important functions do proteins serve?
- How is the information about making different kinds of proteins passed on from parents to children?
- What building block molecules make up proteins?
- What is mDNA, and how is it inherited?
Give students an imaginary section of DNA in a gene and ask them to translate it first into mRNA codons and then into amino acid sequences, using the chart "DNA and RNA Codes for Amino Acids" on pages 6-7 of the article. For example: DNA codons CGGCTAGTAAGA transcribe to mRNA anticodons GCCGAUCAUUCU and then are translated to an amino acid chain: Alanine-Aspartic Acid-Histidine-Serine.
5. Show the video A Mutation Story. Discuss the following as a class:
- What protein acts as an oxygen transporter in humans?
- What causes sickle cell anemia? How might this have originally occurred?
- How is sickle cell anemia inherited?
- Why is the heterozygous genotype for hemoglobin advantageous in some regions of the world? What would this advantage do to the frequency of this allele?
- What role do mutations play in the evolution of humans?
Although people in the United States know about the sickle-cell allele mainly through the experience of African-Americans, this is by no means an exclusively African phenomenon. The same point mutation has apparently arisen independently two or three times in Africa, at least once in the Middle East, and at least once in Asia. In addition, human migration and intermarriage, along with the wide geographic spread of malaria, have distributed and maintained these alleles in many populations, including (but not limited to) many "European-looking" inhabitants of Greece, Spain, Portugal, and Turkey.
6. Summarize the lesson by asking:
- What is the relationship between DNA replication and protein synthesis?
- What surprised you about DNA replication and protein synthesis?
- What questions do you still have?