Molecular Approaches to Evolution

Scientist Simulation

Joseph Glick and Susan Drake

Target age or ability group: General high school biology.
Class time required: 45-50 minutes.
Materials and equipment: Copies of lab (one per two students)
Mouse Genome Map Poster (produced by Science for Life Technologies and available through Gibco BRL Products.
Order/Tech-Line: (800) 828-6686. Fax: (800) 331-2286.
Chart of mRNA codons and the corresponding amino acids
Summary of activity: It is difficult for many students to envision the work of a research scientist, and some occasionally fail to see the relationship between molecular biology and medicine. This activity allows students to imagine themselves working as research scientists by asking them to complete the end-steps of a molecular research project and to interpret their data. The activity emphasizes not only the translation/transcription process, but also the correlation between a single nucleotide substitution and the subsequent consequences.
Prior knowledge, concepts or vocabulary necessary to complete activity: Instruction in basics of DNA manipulation and the steps involved in protein formation should precede this activity. Students should be familiar with the following terms:
messenger RNA transfer RNA introns exons
chromosomes transcription translation mutation
genome genetic markers PCR
Extension/ Comments: You might require students to compare their derived amino acid sequence to a list of known amino acid codes found in mouse proteins. The DNA sequence in this exercise is a known gene that codes for a pituitary hormone that has been found to mutate by a single nucleotide substitution. Known DNA and amino acid sequences for mouse proteins can be acquired using the Internet and World Wide Web. Numerous genome data bases exist relating to DNA sequences of mouse genes. These sites may be accessed by search queries or by using the following addresses:

Reference: Brindle, P., Linke, S. and Monmimy, M., 1993. Nature 364:6440, 821-824.

Scientist Simulation

Note to the student: Imagine yourself in the following scenario:

You are a graduate student at Princeton University pursuing a Masteršs degree in Biology/Immunology. You have a special interest in a new disease in human beings known as Palmer-Fricks disease.

The symptoms commonly associated with the disease are:

  • abnormal growth
  • suppressed growth
  • irregular production of growth factors
  • kidney dysfunction
  • irregular metabolism
  • irregular heartbeat
  • lack of sexual maturation/overdevelopment of sexual organs

You are using a mouse (murine) model to research the disease. The mouse model is analogous to the human disease, and the mouse genome has been quite extensively mapped. Various markers are available to assist you in studying a great number of chromosomal regions in the mouse model.

You have a number of mice (made up of four generations bred at your research center), some of which show symptoms analogous to those symptoms shown in human Palmer-Fricks disease. Also at your disposal are several generations of mice of the same species that do not exhibit any symptoms of Palmer-Fricks disease. You have sacrificed several mice and have removed their pituitary glands to obtain cells from which you can purify DNA. After obtaining the cells, you performed Polymerase Chain Reaction (PCR) on a small portion of your sample.

You are to complete the required steps a genetic research scientist would have to complete under these circumstances. Use any resources available to you (classroom, laboratory, media resource center, etc.). Be sure to think like a scientist, and attempt to justify all your actions with scientific reasoning. Your teacher may ask you to explain your actions (just as a Principal Investigator of a laboratory might ask). You are to complete the questions that follow the initial laboratory activity.

Good luck in your research efforts!

Name Period Class:

I. Normal Gene:

The segment of the mouse chromosome that you have sequenced in the "normal" mice shows the DNA sequence below:

tac tgg tac ctt tgt caa ctt agt gtc gtc cta gct tca cat tgt gca aga cat cgt ctc gta tcg aga cga gta tac gtc tga cca gtt taa aga caa gaa tga gat cga gtc caa aga cat cga cct agt ccg tga cct tct ccg agg ggt cga cac tga gat cat gtc aat gga agt ccg gtt tga cat gtc cag gtc cct caa taa gtc tgt ggt gta ggt agc caa taa gtt agt

A. Transcription: Transcribe the DNA sequence to the corresponding messenger RNA sequence.

B. Translation: Using the table of amino acid codons (supplied to you by your teacher), translate the messenger RNA to the correct amino acid sequence.

II. Abnormal Gene:

The abnormal mice (those showing symptoms of the disease), show the DNA sequence shown below:

tac tgg tac ctt tgt caa ctt agt gtc gtc cta gct tca cat tgt gca aga cat cgt ctc gta tcg aga cga gta tac gtc tga cca gtt taa aga caa gaa tga gat cga gtc gaa aga cat cga cct agt ccg tga cct tct ccg agg ggt cga cac tga gat cat gtc aat gga agt ccg gtt tga cat gtc cag gtc cct caa taa gtc tgt ggt gta ggt agc caa taa gtt agt

What codon is different in the normal vs. the abnormal mice?

How has the codon changed? How is it different?

Identify the type of mutation.

III. Presentation:

You are to present your research findings to the Board of Directors at Princeton University. They will decide if your project deserves future funding based upon the success of your current project.

On a separate sheet of paper, outline the presentation that you will make to the Board. You need not write out your presentation "word for word," but you should list your major points and remember that your success as a student and a researcher depends on your funding.

Possible Extension:

To verify the type of protein coded for, use the Internet to access known amino acid codes for various sequenced mouse proteins. Be aware that the amino acid code that you have obtained may be a partial protein code (as most proteins are made up of thousands of amino acids). If you do not have access to the Internet, ask your teacher for a list of known mouse protein amino acid sequences and attempt to find a match for your sequence.

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