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Were the babies switched? – The Genetics of Blood Types and Skin Color

3 babies with different skin color

In this minds-on, hands-on activity, students learn about the genetics of ABO blood types, including multiple alleles of a single gene and codominance. Then, students use chemicals to simulate blood type tests and carry out genetic analyses to determine whether hospital staff accidentally switched two babies born on the same day.

Next, students analyze the genetics of skin color in order to understand how fraternal twins can have different skin colors. In this analysis, students learn about incomplete dominance and how a single phenotypic characteristic can be influenced by multiple genes and the environment. (NGSS)

Download Student Handout: PDF format or Word format

Download Teacher Preparation Notes: PDF format or Word format

The Teacher Preparation Notes provide instructional suggestions and background information and explain how this activity is aligned with the Next Generation Science Standards (NGSS). We invite comments on this activity. If you would prefer to send your comments or questions in a private message, please write Ingrid Waldron at iwaldron@sas.upenn.edu.

Comments

2024 revision

Submitted by iwaldron on Sat, 02/03/2024 - 6:19am.

The revisions of the Student Handout should increase student engagement and understanding. I have also revised the Teacher Preparation Notes and added recent research results.

Ingrid

2022 revision

Submitted by iwaldron on Fri, 07/01/2022 - 6:35am.

I have clarified and streamlined the previous genetics version of the Student Handout. One important clarification has been to provide more scaffolding for the student analysis and interpretation of the experimental results. The Teacher Preparation Notes provide an optional supplement to the Student Handout that includes additional information and questions about immunobiology. I have clarified the information in the Teacher Preparation Notes, with special attention to clarifying the instructions for preparing the materials for the hands-on experiment.

Ingrid

Where to buy blood

Submitted by Matthew Brown (guest) on Wed, 05/16/2018 - 7:39pm.

I don't understand whether I can buy the supplies for this lab or not... I presume there is some kind of kit available with (simulated) blood and testing substances to yield the required results?

Supplies

Submitted by iwaldron on Mon, 05/21/2018 - 7:14am.

Please see pages 4-5 of the Teacher Preparation Notes for information about where to buy a kit or how to make your own supplies. Pages 3-4 of the Teacher Preparation Notes provide additional helpful information.
Ingrid

Key

Submitted by Danielle Cohn (guest) on Thu, 05/03/2018 - 12:59pm.

How can one go about obtaining a key for this particular lab? Brilliant work by the way.

Key

Submitted by iwaldron on Fri, 05/04/2018 - 9:56am.

Please see the Teacher Preparation Notes for instructional suggestions, background biology and information about how to get the key.

Ingrid Waldron

KEy

Submitted by Isabelle G (guest) on Fri, 04/27/2018 - 3:00pm.

I am homeschooling my child and this is a perfect lab to use! But I unfortunately dont have the Key, Would you be able to send it through my email?

Home schooling Parents

Submitted by iwaldron on Sat, 04/28/2018 - 9:48am.

We are happy that many homeschoolers and their parents have found our activities useful. Unfortunately, we cannot supply keys for our activities to homeschooling parents. Please use the information in the Student Handout and Teacher Notes, plus the information that can be found in a good high school or college textbook, to figure out the answers.

With best wishes for success in your science learning,
Ingrid Waldron

Using Blood test to identify babies worksheet

Submitted by Qetsiyah Yisrael (guest) on Mon, 01/22/2018 - 9:46pm.

could we get the answer key

Were the Babies Switched?

Submitted by Serendip Visitor (guest) on Fri, 11/22/2019 - 4:58am.

Hi.
I also would be pleased to receive the answer key to this workseet.
Thank you.
John Wakefield.

Keys

Submitted by iwaldron on Fri, 11/22/2019 - 8:28am.

Please see the Teacher Preparation Notes which provide learning goals, explanations, background information, instructional suggestions, and information about how to request a key.

Ingrid

key to switched?

Submitted by Serendip Visitor (guest) on Thu, 02/01/2018 - 12:20pm.

I love this activity and my students did too! If I could get the key, I would be most appreciative.

Were the babies switched - key

Submitted by Visitor (guest) on Thu, 02/15/2018 - 4:00pm.

Please send me a key for this worksheet.

Answer key

Submitted by iwaldron on Tue, 01/23/2018 - 6:30pm.

Please see the Teacher Preparation Notes which provide learning goals, explanations, background information, instructional suggestions, and information about how to request a key.

Ingrid

Blood Type Activity

Submitted by Kathleen (guest) on Tue, 05/09/2017 - 12:44pm.

My students loved this activity. It was their favorite assignment of the year. Thank you!

2017 revision

Submitted by iwaldron on Thu, 02/09/2017 - 6:55am.

The questions in the Student Handout have been revised to enhance student understanding and learning. In addition, I developed two versions of the Student Handout – one that includes analysis of the immunobiology and one with very little immunobiology and instead a section on the genetics of skin color that introduces concepts such as incomplete dominance and polygenic inheritance. The Teacher Preparation Notes provide improved instructions for the supplies and experiment.

Blood Typing Activity

Submitted by Lisa Brake (guest) on Fri, 12/16/2016 - 2:23pm.

I am having a hard time following this activity - do you have a key by chance?

Resources for Teachers

Submitted by iwaldron on Sat, 12/17/2016 - 1:42pm.

Please see the Teacher Preparation Notes which provide learning goals, explanations, background information, instructional suggestions, and information about how to request a key.

Ingrid

Were the babies switched

Submitted by Serendip Visitor (guest) on Thu, 07/07/2016 - 5:56pm.

I could not open the Word Doc for the student edition of this lesson. I love the lesson and wanted to print the newer version as a word doc. Thank you.

Link to student handout is fixed

Submitted by Ann Dixon on Fri, 07/08/2016 - 6:31am.

Thanks for letting us know!

-Ann

2016 Revision

Submitted by iwaldron on Fri, 06/03/2016 - 2:38pm.

This activity has a new name, which reflects a major revision to align the activity with NGSS standards and focus the activity on understanding genetics and the biology of blood types.

Time

Submitted by Nicole N (guest) on Mon, 09/14/2015 - 9:45am.

How long does the lab take? Has anyone done it to know how many minutes is required (class periods)?

2013 revision

Submitted by iwaldron on Thu, 12/05/2013 - 2:36pm.

The Student Handout has been streamlined and the questions have been revised to focus on the learning goals and more actively engage students in understanding important genetics concepts. The Teacher Preparation Notes have been expanded to clarify the learning goals, provide additional biology background, and suggest alternative approaches that may be useful for your classroom.

August 2012 revision

Submitted by iwaldron on Tue, 08/07/2012 - 6:04am.

Some of the questions in the Student Handout have been clarified and the Teacher Preparation Notes have been updated with additional information.

Fake blood

Submitted by Serendip Visitor (guest) on Wed, 01/18/2012 - 8:06am.

I wonder if there is some way to make your own fake blood that could be coagulated with vinegar? Then it would not be necessary to purchase the blood typing kits.

Cheap fake blood

Submitted by iwaldron on Tue, 08/07/2012 - 6:02am.

If you have insufficient budget for the recommended kits, you can make the fake blood samples and anti-sera by adapting the instructions to use food coloring, milk, vinegar and water provided on pages 1-3 of "Teachers’ Talking Science – Blood Typing", available at http://www.talkingscience.org/wp-content/uploads/2011/03/tts-bloodtyping.pdf . However, you should be aware that this cheaper alternative is significantly more complicated for you and your students to use; specifically, you will have to designate different antisera for each sample in order to get the desired results.

freaky out

Submitted by Anonymous (guest) on Wed, 04/28/2010 - 8:30am.

as you can see im doing my homework right now so i need the answer cuz im lost xD is about identify babies blood and criminals so if u can help me i'llso freaky happy

2010 revisions

Submitted by iwaldron on Tue, 02/02/2010 - 9:39am.

We have improved the section on genetics of blood types in the student handout. The Teacher Preparation Notes now include possible Extension Activities concerning the inheritance of skin color, so students can learn about polygenic inheritance, independent assortment and incomplete dominance (in contrast to co-dominance for the blood type alleles). These extension activities are worksheets, which we have found to be a useful supplement or alternative to hands-on activities for helping students to learn genetics.

A and B antigens actually are carbohydrate molecules

Submitted by iwaldron on Tue, 11/17/2009 - 12:52pm.

Although the misconception that the A and B antigens are proteins is widespread, it is now well established that this is not true. "The gene that determines ABO ... encodes an enzyme that adds sugar molecules to lipids on the surface of red blood cells. ... The gene that encodes the enzyme, designated I, has three common alleles: I^B whose product adds a lactose; I^A whose product adds galactoseamine; and i which codes for a protein that does not add a sugar.... If a type A individual receives a transfusion of type B blood, the recipient's immune system recognizes that the type B blood cells possess a "foreign" antigen (galactose) and attacks that donated blood cells, causing them to clump, or agglutinate." (quoted from Raven et al., Biology, seventh edition, page 260). Additional supporting information can be found in immunology textbooks.

I would use this blood type

Submitted by Karen Richard (guest) on Tue, 11/17/2009 - 10:18am.

I would use this blood type activity except that the person who typed out the the directions has written that the A and B antigens are "carbohydrate molecules" on the surface of teh RBC. The A and B antigens are PROTEINS.