New Jersey PERFORMANCE ASSESSMENT ALLIANCE

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1 New Jersey PERFORMANCE ASSESSMENT ALLIANCE TWEAKING THE GENES SCIENCE/BIOLOGY Grade Level High School Copyright 2006 by the New Jersey Performance Assessment Alliance. All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage or retrieval system, without the prior written permission of The New Jersey Performance Assessment Alliance unless such copying is expressly permitted by federal copyright law. Address inquiries to The New Jersey Performance Assessment Alliance, 12 Centre Drive, Monroe Township, NJ These performance assessments present prompts that are to be used solely for NJ assessment purposes. No prompts may be disclosed or used for any other reason. By accepting delivery of or using these prompts, the recipient acknowledges responsibility for maintaining assessment security that is required by professional standards and applicable state and local policies and regulations governing proper use of tests and for complying with federal copyright law which prohibits unauthorized reproduction and use of copyrighted assessment materials. 1

2 Prompt Overview and Directions for the Student You are a geneticist at a biomedical company that is working to develop pharmaceutical products that will improve the health and well-being of people around the world. Your company has developed a new antihistamine that could help many people who suffer from allergies, colds, and the flu. This antihistamine must be thoroughly tested before it can be offered to the public. Before you can actually conduct tests of this antihistamine on people, you must first see if it is safe to test on humans. To do this, you must observe how it reacts with human antibodies. Through your research you have found out that one specific protein in the blood of horseshoe crabs is very similar to antibodies found in humans. If you can safely test the new antihistamine on the horseshoe crab protein, you will be able to determine if the drug is safe to test on humans. Your biomedical company has developed a genetically-modified horseshoe crab with a life span of years and reaches adulthood and sexual maturity in only two (2) years. The company needs at least two thousand (2000) crabs to harvest enough antibody for safety testing. You will be able to use these horseshoe crabs to determine the fastest way to collect enough horseshoe crab protein to begin testing. There are problems, however. First, the protein is present only when expressed by a recessive gene in the horseshoe crabs. In addition, there are only four (4) adult horseshoe crabs that are available for breeding and all four have different genotypes. Worse still, all of these horseshoe crabs have gene combinations that express the dominant trait in their phenotypes. This, too, is a problem! Why? Remember that the form of the protein that your company needs is the result of the recessive gene. The antibody from the dominant gene is of no use to your company! 2

3 STUDENT PROMPT YOUR TASK: Use the FACTS on the next page to help you complete the following: Find a way to breed enough horseshoe crabs through genetic crossings of the original four and their offspring to produce enough horseshoe crab protein needed for the safety testing of the new antihistamine using an efficient process. Show the Punnett Squares for each mating/genetic crossing. The Punnett Squares must display each genotype with the number of crabs and the percentages produced in that crossing. Create a detailed written explanation of the process or steps that you used to solve this problem. NOTE: There are many ways to solve this problem. Your answers may vary depending upon the process you use. Good luck! 3

4 STUDENT PROMPT USE THE FOLLOWING FACTS TO HELP COMPLETE YOUR TASKS: The biomedical company needs at least two thousand (2000) horseshoe crabs to collect enough protein for testing. The four original horseshoe crabs have these genotypes and sex: HH: Male Hh: Male HH: Female Hh: Female The dominant gene for the protein is represented by the capital letter H. The recessive gene for the protein is represented by the lower-case letter h. These adult horseshoe crabs produce approximately ten thousand (10,000) eggs in a single mating. On average, one thousand (1000) eggs hatch and only one hundred (100) survive to adulthood. One-half of the surviving crabs will be male and one-half will be female. The life span of the genetically-modified horseshoe crab is years. It takes these genetically-modified horseshoe crabs approximately 2 years to reach adulthood and sexual maturity. Horseshoe crabs can only mate in adulthood when they reach sexual maturity. These horseshoe crabs mate and reproduce only once a year throughout adulthood. The protein can be harvested from adult horseshoe crabs only. 4

5 TWEAKING THE GENES Allele - One possible characteristic for a gene. GLOSSARY OF TERMS Antibody - An immunoglobulin; a protein that neutralizes certain toxins, viruses, and bacteria or other foreign cells. Antihistamine - A drug which is used to reduce or prevent inflammation. Dominant gene - A form of the gene that is always expressed when present in the genotype. Gene - Unit of DNA that encodes one or more proteins which may control characteristics or traits of the individual organism. Genotype - The genetic presence of specific alleles, represented by a letter pair denoting the form of allele in the genotype. Inheritance - The passing on of genes from one generation to the next. Punnett Square - A chart which shows all of the possible genetic combinations of offspring that result from the parents in a genetic cross. Phenotype - The result of the expression of a particular gene; it is determined by the genotype. Recessive gene - A form of the gene that is expressed only when both recessive alleles are present in the genotype. If a recessive gene is present with a dominant gene, it will be masked and therefore will not be outwardly expressed. 5

6 SCORING GUIDE (RUBRIC) Content Process Format Creates accurate Punnett Squares. Determines correct genetic crosses to produce the appropriate offspring. Determines accurate percentages of genotype and phenotype for all offspring in each generation. Uses appropriate reasoning to describe a timely process of mating that is needed to produce the desired number of horseshoe crabs from the original four parents efficiently. Clearly explains relationships between all generations. Correctly calculates all mathematical operations. and writing presented in an organized way that is easy to understand. Few mechanical errors. Creates accurate Punnett Squares. Determines correct genetic crosses to produce the appropriate offspring. Minor errors in determining the percentages of genotype and/or phenotype for offspring in any generation. Uses appropriate reasoning to describe a timely process of mating that is needed to produce the desired number of horseshoe crabs from the original four parents efficiently. May correctly explain relationships between some or all generations. May have minor errors in mathematical calculations. and writing presented in an organized way that is easy to understand. Errors are evident but do not interfere with meaning. Includes Punnett Squares but may lack proper expressions of offspring. Genetic crosses may be effective but not be the most appropriate. Errors are apparent in determining percentages of genotype and/or phenotype for offspring. May show appropriate reasoning in describing the mating process needed to produce desired number of horseshoe crabs from the original four parents. Explanations of relationships between generations may be vague, unclear or inaccurate. May have errors in calculations. and/or writing presented in a disorganized manner; OR may be incomplete OR may be missing. Errors make it difficult to understand writing or graphics. Punnett Squares are ineffective. Inappropriate genetic crosses. Significant errors throughout. Gives unrelated details to support Punnett Square(s). Lacks appropriate reasoning to show understanding of reproduction and/or genetic inheritance in horseshoe crabs. Major errors in calculation or lacks any computation. and/or writing are incomplete or missing entirely. Errors in writing greatly interfere with the meaning of the written work. 0 No judgment can be made 6