Carlson and Greenwald, GENA Workshop 2010

I. Introduction: Zebrafish and the Value of Model Systems: Zebrafish are small, relatively inexpensive to maintain, and produce large amounts of transparent embryos that develop rapidly outside of the body. For these reasons, they make a great resource for studying development and genetics in the high school classroom. We developed a one-week module using zebrafish to give high school biology students a hands-on opportunity to explore Mendelian genetics while gaining an appreciation for developmental biology (a subject not often taught in the high school classroom). Our module began with two lessons aimed at introducing model organisms and developmental biology. During these lessons, we used popular media and pictures to ask students how it is possible to use animals distantly related to humans to model human systems. We also gave the students an opportunity to observe and draw/record their observations of zebrafish embryos at different developmental stages. The last three days involved the students observing and scoring embryos for a mutant phenotype. Using their individual numbers and the class results, the students were asked to make a prediction about the mode of inheritance of the mutation. We finished the module by discussing data analysis, experimental error, and linked our results to a discussion on human development and disease. The skills the students developed in our teaching plan included data analysis, interpretation of genetic data, animal husbandry, and the use of a stereoscope. The materials required for this module include mutant and wild type zebrafish embryos (at 24hpf, 48 hpf, 72hpf and 5 dpf), Petri dishes, embryo water, and stereoscopes. This one-week lesson plan is relatively inexpensive and exposes high school biology students to developmental biology while giving them a hands-on opportunity to work with genetic analysis. II. Students’ Misconceptions to be Addressed in the Unit:

1. Mendelian Genetics: Mendel’s Ratios are Exact 2. Model Systems: If you want to understand humans, you should use humans.

III. Minnesota State Standards to be Addressed in the Unit:

1. Life Science: IV.D.6: The student will use Mendel’s laws of segregation and independent assortment to determine the genotype and phenotype of a monohybrid cross. 2. Life Science: IV.D.7: The student will differentiate between dominant, recessive, codominant, incompletely dominant, polygenic and sex-linked traits. 3. History and Nature of Science: I.B.3: The student will apply mathematics and models to analyze data and support conclusions.

IV. Major Science Concepts Addressed in the Unit:

1. Evolution: Common ancestry and the conservation of genes throughout evolution.

2. Mendelian Genetics: Dominant vs. recessive traits, calculating Mendelian ratios and predicting inheritance patterns.

3. Development Biology: What is it? Stages of embryological development. V. Learning Objectives of Unit:

1. Students will be able to do Punnett Squares and calculate ratios based on real observations -Students will receive a petri dish of zebrafish embryos to score for the phenotype and calculate ratios to determine whether the phenotype is dominant or recessive. 2. Students will be able to describe the effect of sample size on data analysis -Students will analyze data collected on their own. We will then pool the data from the class and reanalyze. 3. Students will be able to use evolution (common ancestry) to explain how model systems are used to study genetic questions VI . Student Skills That will Be Learned/Reinforced in this Unit: 1. Punnett Square analysis 2. Data analysis 3. Interpretation of experimental genetic data 4. Knowledge of animal husbandry 5. Use of a stereoscope

VII. Prerequisite Skills For This Unit

1. Introduction to Mendelian genetics and familiarity with Punnett squares. 2. Knowledge of the central dogma(DNA RNA Protein) and universality of

genetic code.

VIII. Timeline for the Unit: Based on a schedule with daily 45 minute periods (Implemented over a 5 day period in January of 2010 in an IB (International Baccalaureate) Biology Classroom of 11th and 12th grade students. This is the second year of high school biology for these students). *This unit was taught in collaboration with the University of Minnesota Zebrafish Core Facility (Director: Dr. Lisa Schimmenti-Another GENA geneticist). DAY 1: Engagement

1. Administer Pre-test on: Model systems, Developmental Biology and Mendelian Genetics (Supplementary material: Pre-test) *See Supplementary Material: Powerpoint Day 1 2. Introduction to Kerri Carlson (geneticist): How did Kerri arrive at her position, what does she do all day and what does she study. ENGAGEMENT: Prior to day 1 students were given newspaper articles describing the use of model systems in the study of genetics and asked to read them prior to coming to class.

A. Scientists Create See-Through Fish, Watch Cancer Grow: Jeanna Bryner, Live Science.

B. Transparent Zebrafish a Must-See Model for Atherosclerosis: Debra Kain C. Researchers Say They Can Cure Cancer in Mice: WESH.com

Asked them to consider the question: How can we study humans using mice and fish? 3. Introduction to Model Systems: Classroom discussion with Kerri about what model systems are, how they are used, and why geneticists use them. Finished with an introduction to evolution and common ancestry as it relates to model system use. DAY 2: Exploration 1. Introduction to developmental biology and the zebrafish as a model system for studying developmental biology and genetics by Kerri (Supplementary Material: Powerpoint Day 2). 2. Kerri brought in both adult and wild type zebrafish embryos for students to observe (through collaboration with the University of Minnesota Zebrafish Core Facility).

A. Adult fish: Students were able to observe wild type zebrafish, GloFish (zebrafish genetically engineered to express fluorescence proteins), and transparent zebrafish (the same fish that were discussed in the newspaper articles they were given to read).

B. Zebrafish Embryos: Embryos at different stages of development (<24hpf (hours post fertilization), 24hpf, 72hpf, 5dpf) were available in petri dishes for students to observe using stereoscopes Barry had available in the classroom. [

A poster showing zebrafish embryos at different stages of development was available in the classroom. Students were asked to draw a picture of the embryos they observed and to use the poster to determine the stage of development of the embryos they observed. DAY 3: Exploration -Preparation for Day 4 1. Review of Mendelian Genetics: Students were given a worksheet with Mendelian Genetics Problems to work on in small groups. Kerri and Barry circulated to answer

questions. Answers were discussed in a large group (Supplementary Material: Punnett Squares): 2. Introduction to Experiment Students will be participating in on Day 4:

A. Video: 15 minute video showing animal husbandry of zebrafish and how embryos are collected so the students will understand how we collected the embryos that they will be working with. *This video was prepared by Kerri and Barry during the summer of 2009 at the University of Minnesota in collaboration with the UMN Zebrafish Facility. C. Introduction to the mutant fish the students will observe on Day 4.

(Supplementary Material Powerpoint Day 4). For more details see Day 4.

DAY 4: Exploration 1. Students observed and counted mutant zebrafish embryos (3 dpf) in groups of 2. Each group received approximately 20-40 embryos. They were asked to use their data to make a prediction about the mode of inheritance (dominant or recessive) for the mutation. Students then combined their data with the entire class and reassessed their prediction. All the embryos were from genetically identical parents and could be considered siblings making analysis possible. -Students received handout on the Zebrafish Lab (Supplementary Material: Zebrafish Lab) Details about the mutation used -We used zebrafish noitu29 mutant zebrafish embryos. These fish have a mutation in the pax2 gene. This mutation is autosomal recessive and results in embryos with severe edema, brain defects, ear defects, and kidney development. This edema, or swelling is relatively easy to observe by day 3 of development. In order to aid students in counting, we used preserved zebrafish embryos. Because the embryos were washed several times after fixation and kept in non-toxic phosphate buffered saline, students did not need to use protective equipment. Students should see an approximate 3:1 ratio of wild type to mutant zebrafish. -We chose to use this particular mutation for two reasons. First, we wanted a phenotype that would be relatively easy for the students to observe. Second, mutations in pax2 are also a cause of human disease and allows us to bring the discussion back to human genetics and disease on Day 5. DAY 5: EXPLANTION/EXTENSION 1. Results from Day 4 were discussed: As a class, we discussed mode of inheritance of the mutation, importance of sample size (differences between individual group results and the large class results), and sources of experimental error. The classroom data collected supported the predicted 3:1 ratio for a recessive mutation.

2. Kerri wrapped up the experiment by bringing the discussion back to model systems and human development and disease (Supplementary Material: Powerpoint Day 5). -Discussion of Evolution, Common Ancestry and the conversation of the PAX2 gene (the gene mutated in the zebrafish embryos they observed) between zebrafish, mice and humans. A protein alignment of the three proteins was presented to the students. Kerri then discussed the similarities and differences between the zebrafish pax2 mutants, and mice and humans that have mutations in the PAX2 gene. [Mutations in PAX2 caused Renal-Coloboma Syndrome in human patients] Finally, as a class we discussed how using the zebrafish to study pax2 may allow researchers prevent and or treat Renal Coloboma syndrome in humans. POST ZEBRAFISH MODULE Day 6: Post-test was administered to students and students received the guidelines for the laboratory report that they were to write about this experiment (Supplementary Material: Zebrafish Lab Write-Up). ASSESSMENT 1. Summative Assessment: -Pre/Post Test: The students improved 15% overall. Some of the material on the test was material that many students should have had previously and so in general they performed well on the pre-test. -Laboratory Report: Students were asked to write up their results from the Day 4 experiment including drawings, small group data, class data, and a discussion of mode of inheritance and experimental error. 2. Formative Assessment: -Kerri and Barry informally asked questions while students observed embryos and worked on Punnett square worksheet.

Carlson and Greenwald, GENA Workshop 2010 FINAL REFLECTIONS Overall, we had a very positive experience. The students were engaged in the zebrafish activities from beginning to end. They were appreciative of a college professor taking the time and making the effort to be in their high school classroom. Some representative student comments from the end of the quarter evaluations are attached. In general the student response was very favorable. Some things that worked well include the following… • The value of hands-on experience with something completely new. The students realized that this was something beyond the normal high school curriculum. • Learning the basics of Mendelian genetics beforehand was very helpful to bring the students up to speed to do the lab. •The fact that this was a second year biology class allowed to us to make some accurate assumptions about prior knowledge and also allowed us to work with a population of students that were more mature and engaged with the material throughout the unit. •By asking students to do a specific task (drawing the zebrafish embryos and determining the stage of embryo development) encouraged students to study them more carefully. •By collecting small group data and comparing them to the combined class data, students were able to see the importance of sample size on experimental results. •By using a zebrafish mutant line that correlated with a human disease, it was easy to make the connection between model systems and human genetics. •These activities opened up the door for a discussion about the ethical treatment of animals in scientific research. Areas of improvement… • Consideration of which mutant embryo to use: It is important to use a mutant zebrafish line that has a correlation with human disease but the line we chose (tu29) is difficult to breed. They do not give embryos reliably. This makes it difficult to time the lesson to have live mutant embryos for students to observe. • Revision of the engagement piece: Perhaps including a small group activity to discuss the newspaper articles the students were asked to read before opening it up to class discussion. This would encourage students to participate more fully in the class discussion. • It would be nice if the embryos brought to the classroom for observation could be raised in the classroom b the students to adulthood. Also, it would be nice to have a tank of adult zebrafish in the classroom throughout the semester. Challenges… •It was very important to have a positive collaboration with the University of Minnesota Zebrafish core facility. From the geneticist standpoint it would be nice to be able to provide your own embryos and fish for the classroom.

•Five days can be a significant time commitment for the geneticist to spend in the classroom but is important for the first run through of the lesson plan. In subsequent years, the lessons could be modified so that the educator took a greater lead. Considerations for the future… • If the geneticist is able to visit the same group of students a second time, a student designed inquiry based experiment could be developed. Our GENA experience was very positive both for us as participants and for the students in Barry’s class. We look forward to continuing our collaboration next year.

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Kerri Carlson, PhDBiologist, Teacher, Reader, Dog lover, Reality TV watcher

My Journey to Science….

Archaeologist Human Geneticist

My Current Home

H.S. College Grad School Research

What do I do all day… What do I do all day…

Every day is different!

My favorite things about being a biologist…….

Genetics of Eye Development

COLOBOMAS

1. What genes are involved

2. How can we prevent/treat?

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Studying Genetics

WHAT DO YOU NEED?

Studying Genetics

WHAT DO YOU NEED?• Multiple Generations• Specific Matings

ex. Smooth X Wrinkled peas

Human Genetics

1. Why is it important?

Human Genetics

1. Why is it important?

*Human health*Understanding ourselves

*Studying evolution

Human Genetics

2. What challenges do we face?

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Human Genetics

2. What challenges do we face?-Long life span

-Long generation time-Ethical considerations

WHAT DO WE DO???????

What Do We Have in Common?

MODEL ORGANISM:Organisms studied to understand biological questions. Information learned can then be applied to other organisms.

We are all model organisms!!!

Model System Characteristics

What do you think?

What makes me a good model?

1. Short life-cycle2. Techniques to manipulate

genetically3. Small size4. Easy to take care of5. Cheap6. Often, large amounts of offspring

?

How is this possible……

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How is this possible?

EVOLUTION AND COMMON ANCESTRY

What’s coming up this week…

1. Zebrafish: A model organism2. Exploration of one zebrafish mutation

3. How does this relate to humans?

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Developmental BiologyJanuary 20th Developmental Biology

1. What is it? 2. How do scientists study it?3. What is a zebrafish?

http://www.ndpteachers.org

HOW DOES THIS HAPPEN?

http://www.ndpteachers.org

HOW DOES THIS HAPPEN?1. Cell Division (MITOSIS): 1 to >10 trillion cells!!!!!!!!!

2. Differentiation: Not every cell looks or does the same thing!

Neuron Heart cell

http://heart.sdsu.edustanford.edu

3. Morphogenesis: Each anaimal has a specific shape.

Early Development WHAT CONTROLS THESE PROCESSES?

• GENETICS!

• ENVIRONMENT!

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HOW CAN WE STUDY THESE PROCESSES?

• Challenges……

How do we study development?

• Learn from other organisms (EVOLUTION)-Mice-Chicken

What is a zebrafish?Freshwater minnow from East India

1820’s

First Described

1905

Europe aquarium 

fish

1970’s

George Stresigner

Genetics!

Today

Lots of people use!

Human vs. ZebrafishSIMILARITIES DIFFERENCES

MRC Human Embryo Bank / Wellcome Photo Library ZFIN.ORG

-Vertebrates (backbones)

-Embryonic development is similar

-Similar genetic makeup

-Specialized to live in water

-Develop outside the body, hatch

17hpf1 month

Why Do We Use Zebrafish?1. Small and relatively hard to kill

2. Do not cost a lot of money to keep and raise

3. Each set of parents produce a lot of babies

4. Develop quickly and we can see it all.

5. Can manipulate genetically

Should look familiar!

Zebrafish MiceCost /yr*

(1000 animals)$9000 $42,340

Embryos/mating 200-300 6-8Embyos/3months 3600 48 max

Development Time

72 hours 21 daysGeneration Time 2-3 months 6 weeks

*estimated based on animal care costs at the UMN during the 2008-2009 year.

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Rapid and External Development

RO Karlstrom and DA KaneDevelopment (1996) 123:461

First 17 hours of development

What can we study?

Now its your turn…….

1. Take a look at the adult fish that I have brought up front.

1. Observe the embryos that we have provided for youA. How old do you think they are (use posters as a

clue)B. Draw a picture of the embryo you see.

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What gene are we looking at?Zebrafish = pax2a

Important for: Brain, Eye, Ear, Kidney Development

PREPARATION FOR TOMORROW PREPARATION FOR TOMORROW

There are two alleles we will be looking at…

pax2aWild type allele

pax2atu29aMutant allele

WHAT ARE THE THREE POSSIBLE GENOTYPES?

Edema

Embryos are 3 days old

Mutant

Wild type

WHAT YOU WILL SEE…… (Phenotype) Up Close and Personal With The Mutant(You probably wont be able to see)

One Day Old Embryo

Mutant Fish

Three Day Old Embryo

Mutant Fish

Up Close and Personal With The Mutant(You probably wont be able to see)

Coloboma

TOMORROW

• You will look at your own embryos– How many mutant?

– How many wild types?

• Is the mutant “phenotype” dominant, recessive?

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�Zebrafish pax2atu29a Mutation‐Recessive‐Man‐made mutation‐Mutation creates truncated protein (no function)‐Phenotype: Eye, Brain, Kidney, Ear

WHY DO WE CARE?!!!!!!  

Homolog• Other organisms (fly, mouse, human) have a Pax2a gene (due to common ancestor)

HUMAN & MOUSE86% Identical

ALL BECAUSE OF EVOLUTION………..

HUMAN & FISH74% Identical

Mouse Pax2Mutations

+/‐ ‐/‐ ‐/‐

14.5 day old mouse embryos (eye)

Pax21Neu Incompletely Dominant Mutation(Naturally Occurring)

HETEROZYGOUS (Kidney and eye phenotype)HOMOZYGOUS (Kidney, eye, brain, ear phenotype): LETHAL! NOT BORN

Renal Coloboma Syndrome(Human PAX2Mutations)

normal

coloboma

EYE KIDNEY EAR

1211109876321 54

insG619 insGG619 delG619

602delT

611delTdel658-663

del673-694

832delG

C886T

G719A

768ins gagacc

1104delC C1289T

C1318T

C1566A

LOTS OF DIFFERENT MUTATIONS HAVE BEEN IDENTIFIED IN PAX2

**ALL LEAD TO A NON FUNCTIONING PROTEIN!******

Renal Coloboma Syndrome(Human PAX2Mutations)

SAME AS MOUSE

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Mode of Inheritance

Mutation  MutationType

Genotype: Heterozygous

Genotype:Homozygous 

MutantHUMAN Incomplete (?)

DominanceNatural  LOF Eye, ear, kidney 

phenotypeLethal

MOUSE Incomplete Dominance

Natural LOF Eye, kidney phenotype

Lethal

FISH Recessive Man‐made LOF No phenotype Eye, kidney, ear, brain (wont survive to adult)

A COMPARISON……..

SIMILAR BUT ALSO DIFFERENT!

THANK YOU MODEL SYSTEMS!!!!!!

Name: ____________________________________________ Period: ____ IB Biology I Winter Quarter 2009-2010

Model Systems, Developmental Biology, and Mendelian Genetics Pre/Post test The two purposes of this pre-test are (1) to see what you already know about these topics and (2) to be able to compare your beginning knowledge with what you will learn after we have finished studying these subjects. Your grade on this pre-test will be based on completion, not on score. Multiple Choice Circle the answer that best answers the question or completes the sentence. 1. In developmental biology, differentiation refers to

A. a cell becoming specialized for a specific job in the body. B. a cell dividing by the process of mitosis into two daughter cells. C. a group of cells forming a specific shape such as an eyeball. D. the death of a cell in the body.

2. Which of the following characteristics make zebrafish a good model system for studying human

development? A. Zebrafish embryos develop inside the mother’s body. B. Zebrafish embryos take 9 months to develop before they are born. C. Zebrafish embryos rely on their mother for food during development. D. Zebrafish embryos are transparent (you can see through them).

3. Why can geneticists use model systems to study questions about human development and disease when

model organisms are so different from humans? A. Model organisms and humans both live on Earth and therefore must be the same biologically. B. Many genes and processes are the same between model organisms and humans because of evolution. C. Many model organisms eat the same food as humans. D. Model organisms get the same diseases as humans.

4. A desirable characteristic of a model organism used by a geneticist is

A. that it’s inexpensive to house and feed. B. its small size C. its short-life cycle D. All (A, B, C) of the above are correct.

For questions 5 through 8, please use the following information: The gene that we are studying in our mutant fish is: pax2a (denotes the wildtype allele) and pax2atu29a (denotes the mutation) 5. If the mutation is inherited in a Mendelian fashion and if the mutation is a recessive allele, which of the following would represent a zebrafish that was a carrier (only) for the mutation:

A. pax2a, pax2a B. pax2a, pax2atu29a C. pax2atu29a, pax2atu29a D. None of the above would be carriers.

6. Which of the choices below would represent a heterozygote? A. pax2a, pax2a B. pax2a, pax2atu29a C. pax2atu29a, pax2atu29a D. None of the above would be a heterozygote.

7. If two homozygous dominant (for the trait in question) fish mated, what would be the probability of their offspring expressing the mutation (as a phenotype)? A. 0% B. 25% C. 50% D. 100% 8. Which of the choices below would represent an organism with a homozygous recessive genotype?

A. pax2a, pax2a B. pax2a, pax2atu29a C. pax2atu29a, pax2atu29a D. None of the above would be a homozygous recessive.

9. When comparing a model organism to the organism in question (in this case, zebrafish to human beings), the mutation being studied A. is expressed (its phenotype) the same way in both organisms. B. has the same DNA sequence in both organisms. C. has the same amino acid sequence in both organisms. D. None of the above answers are correct. 10. Assume that a zebrafish embryo has two different alleles for the gene we are studying, so its genotype is pax2a, pax2atu29a. The two different alleles came A. from different autosomes (such as one allele being from chromosome #1 and the other allele

being from chromosome #2) B. from the same locus on the same chromosome; one allele came from the embryo’s father, one

came from the embryo’s mother C. from a single pair of sister chromatids D. from X and Y sex chromosomes

NAME: ________________________________ Period:____ IB Biology Winter 2009 - 2010

THE STUDY OF MONOHYBRID CROSSES USING PUNNETT GRIDS (SQUARES)

Notes: Straight thumb is a dominant trait. In other words, when the genotype is either TT or Tt, the phenotype is a straight thumb. Hitchhiker’s thumb is a recessive trait. In other words, when the genotype is tt, the phenotype is a hitchhiker’s thumb.

Rolled tongue is a dominant trait (genotype RR or Rr results in rolled tongue phenotype). Unrolled tongue is a recessive trait (genotype rr results in unrolled tongue phenotype). 1. Using the Punnett grid, show the cross that will result in 100% of the offspring being heterozygous (Tt) for straight thumb.

What are the parents’ genotypes and phenotypes? 2. Using the Punnett grid, show the cross that will result in 50% of the offspring having straight thumbs and 50% of the offspring having hitchhiker’s thumbs (tt).

What are the parents’ genotypes and phenotypes?

3. If Mr. and Ms. Knight have unrolled tongues, what types of tongues will their offspring have? Show your answer using the Punnett grid below:

For parts a, b, and c of Problem #4, Mr. and Ms. Knight have rolled tongues! 4.a. If Mr. and Ms. Knight have rolled tongues and all of their four offspring have rolled tongues, what are the possible genotypes of the parents? Show one possible Punnett grid.

b. What is another possible combination of parental genotypes resulting in all four offspring having rolled tongues? Show the Punnett grid for this alternative combination.

c. What is the least likely (but still very possible) parental genotypes which could result in all four offspring having rolled tongues. Hint: it’s a matter of probability and statistics.

d. What combination of parental genotypes will result in all offspring having unrolled tongues?

Definition Test cross: testing a suspected heterozygote plant or animal by crossing it with a known homozygous recessive (aa). Since a recessive allele can be masked (as in a carrier), it is often impossible to tell if an organism is AA or Aa until they produce offspring that have the recessive trait. 5. In fruit flies, the allele for straight-wings (ST) is dominant over the allele for curled wings (st). Show the testcross (Punnett grid) made of a straight-winged male parent of unknown genotype with a homozygous recessive (purebred) curled wing female parent.

a. What ratios of genotypes can you expect from this cross if the male parent is

homozygous dominant? What is the ratio of phenotypes in this case?

Genotypic Ratio _________________________ Phenotypic Ratio _________________________

b. What ratios of genotypes can you expect from this cross if the male parent is

heterozygous? What is the ratio of phenotypes in this case?

Genotypic Ratio _________________________ Phenotypic Ratio _________________________

IB Biology I Winter Quarter 2009-2010 Model Systems, Developmental Biology, and Mendelian Genetics Lab

Introduction For the past week or so*, we have been learning about zebrafish and how they are utilized as a model system for human development, health and disease. We have read about recent scientific breakthroughs that have resulted from the use of zebrafish or mice as model systems. We have observed and drawn wildtype (normal) day-old zebrafish embryos under the binoculuar (stereo) microscope. We have studied the mutation known as pax2atu29a that is responsible for defects in brain, heart, and eye development in zebrafish embryos. A mutation in this gene causes retinal coloboma in humans. We have related the pax2atu29a mutation to our studies of Mendelian genetics, including the use of Punnett grids. Today, we will have the opportunity to observe and sort 3-day old zebrafish embryos. We have been told that the pax2atu29a mutation is inherited in simple Mendelian fashion. Our main task, using the collected data from the entire class, will be to predict whether the mutation is dominant or recessive.

Procedure Each group of two students will be given a number of randomly collected 3-day old zebrafish embryos from crosses of zebrafish parents that had at least one copy of the mutant allele. Some of these embryos will clearly have the mutation, based on their (clearly visible) phenotypes. The phenotypes of some of these embryos will be normal (i.e. they will appear phenotypically wild). Your tasks will be to: 1. Observe the embryos, comparing them to the micrographs that will be projected on the screen, until

you are comfortable distinguishing wildtype and mutant organisms. 2. Draw examples of a wildtype and mutant fish. 3. Sort and count the embryos into wildtype and those displaying the pax2atu29a mutation

Data Collection and Processing

4. Record your data (i.e. how many wildtype?; how many mutants) for your group; then add your data to the class spreadsheet that will be available on one of the computers.

After your data has been collected and as part of your lab write-up, present your data, as well as the class

data set in a clearly labeled table. Conclusion and Evaluation

5. Predict whether the mutation is dominant or recessive, using the class data set and the observed ratios of wildtypes to mutants. If you predict that the mutant allele is dominant, what is (are) the genotype(s) of the mutant fish? If you predict that the mutant alle is recessive, what is (are) the genotype(s) of the mutant fish?

6. Propose a cross (mating) to confirm your prediction. 7. If your group’s ratio and/or the class ratios of wildtype to mutant phenotypes is not as exact as you

would expect from the expected Mendelian ratios, propose possible explanations.

Evaluate Experimental Errors and Uncertainties

8. What are sources of experimental errors? Think about what may have been done to prepare the embryos for you to observe today, as well as what you did in class. Consider human errors,

systematic errors, and random errors (see the back of this sheet for explanations and examples). ______________________ *with the guidance of Professor Kerri Carlson from St. Thomas University and with support from the University of Minnesota’s Core Zebrafish Facility

source: http://intranet.canacad.ac.jp:3445/BiologyIBHL2/738

Zebrafish Lab Write-up, Due Monday, February 1st Typed is better, but neatly handwritten is okay, too. Include your drawing(s) of zebrafish embryos. Use scientific language (formal). Include the data sheet, but create your own data table with your group’s data and your class summary data. Introduction

–What’s the question you were asking?

–Did you have a working hypothesis? Materials and Methods (“Procedure”)

–Be specific about materials (stereoscope or binocular microscope with 10X and 30X magnification, probes, zebrafish embryos at what stage (how many days old)?, other stuff?

–Methods: what did you do? Data Collection and Processing

–Include data sheet handout

–Focus on your individual group and class Conclusion and Evaluation ---What is the answer to your question posed in your Introduction? How did your hypothesis hold up? ---The effect of sample size (very important!)

–This is where you can bring in the differences among the 3 data sets ---Some of what you might discuss: From the data, do you think that the mutation is dominant or recessive? Given your answer in #1, what do you think the genotypes of the parents are? Based on your answers to #1 and #2, suggest a cross that would help to verify your prediction. Hint: one of the parents in this suggested cross would be the mutant. What would the other parent be and what expected ratios of mutants and wildtypes would you expect? Experimental Error ---Propose an explanation to explain the differences in the data sets for the 3 classes (remember each class was looking at the same embryos) ---What are some sources of experimental error?