Reuniting a Family

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Reuniting a Family

Oct 02 2014

Source: admin

Summary Information

Keywords:

genetics, DNA, fingerprinting, blood typing, forensics

Topic:

Biology

Estimated Time Required:

1-2 hours

Target Grade (Ages):

Grade 8 (Ages 13-14)

Diversity Indicators:

This lesson engages students with a real-life scenario complimentary for visual-spatial & interpersonal learners. A ruler should be provided for students with perception or vision difficulties, or the DNA sample strips can be enlarged with a photocopier.

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LESSON

Goals and Prerequisites

Goals:

Students are introduced to the problem of identifying missing persons. They read a fictional story of children that have been separated from their parents during a war. Their job is to help reunite the parents and children through a scientific investigation. Students are comparing the pros and cons of using blood typing compared to DNA fingerprinting and ultimately answering the question: Which method is more effective in identifying missing persons?

Prerequisites:

Students should:

Understand the difference between regular fingerprinting and DNA fingerprinting
Have general, working knowledge about DNA and blood types
Have some background knowledge of inheritance of DNA and chromosomes (i.e. children receive 23 chromosomes from the sperm and 23 chromosomes from the egg)
Have some background information of dominant and recessive alleles.

Instructional Objective(s)

Students will:

Match offspring DNA fingerprint to parents
Understand half of an offspring’s genetic material comes from the mother and half from the father.
Know the different blood types: A, B, AB, O
Understand the general differences between blood typing and DNA fingerprinting
Identify the pros and cons of different methods of identifying persons (DNA fingerprinting or blood typing).

Instructional Resources

Background:

DNA (Deoxyribonucleic acid) is a chemical structure found in the chromosomes which are found in the nucleus of the cell; it’s a piece of a chromosome that dictates a particular trait otherwise known as a gene. DNA is a double helix structure. It looks like a twisted ladder; two strands of genetic material are spiraled around each other. Each strand contains a sequence of bases (also called nucleotides). A base is one of four chemicals (adenine, guanine, cytosine and thymine). The two strands of DNA are bonded at each base: Adenine (A) will only bond with thymine (T), and guanine (G) will only bond with cytosine (C).

DNA fingerprints provide strong evidence for identification, paternity testing and criminal identification. Every individual has a unique chemical makeup or "barcode" of these chemicals. Scientists extract the DNA from a cell, place it in an agar gel and use electricity to move the DNA. The longer pieces move faster than the slower pieces. The DNA is then stained and the result looks like a bar code. Some bands are darker and others are lighter.

Blood Type is a classification of blood based on the antigens and antibodies in red blood cells. The antigens are located on the surface of the red blood cells and the antibodies are in the blood plasma. Individuals have different types and combinations of these molecules. The blood group you belong to depends on what you have inherited from your parents. Each blood type is either positive "+" (has the Rh protein) or negative "-" (no Rh protein). This method of testing is less expensive than DNA fingerprinting but does not give an exact match for identification purposes.

Two copies of the blood type genes are inherited to the offpsring, one from each parent. The possible combinations of alleles produce blood types in the following way:

Blood Type Alleles

Type A AA or AO (A is dominant over O)

Type B BB or BO (B is dominants over O)

Type AB AB (A and B are co-dominant)

Type 0 OO (O is recessive)

For part of this lesson, students will be examining vials of "blood". The blood vials are just for a visual and will have to be labeled by the teacher to show different types, but the mixtures are not different. All the "blood" will look and be the same but the students will be able to tell them apart by the labels. The fake blood is just to increase student interest, engagement and create a visual.

Materials:

Student Worksheet
DNA Fingerprint Strips
Project Rubric
Blood Typing & DNA Fingerprinting Stations (See below.)

For Blood Typing Station

Laptop
10 vials of “blood” for visuals: one for each parent and one for each of the eight possible children. (For "blood" you may purchase fake blood or mix ketchup, bbq sauce, soy sauce with a bit of water or corn syrup; there are plently of online recipes. For example, I recommend a non-toxic recipe.
Labels for blood vials:
- Naomi (Mother):A
- Gabriel (Father): O
- Girl 1: AB
- Girl 2: A
- Girl 3: O
- Girl 4: B
- Boy 5: AB
- Boy 6: A
- Boy 7: AB
- Boy 8: O

For DNA Fingerprinting Station

Cut out children's DNA fingerprints strips.

*NOTE: Only cut out children's strips. Place parents DNA fingerprints sheet on the table so the students can place the children's DNA fingerprints in the dotted rectangular box in between the two parents.

Picture of actual DNA fingerprint (for visual and comparison purposes)
Ruler

Procedure:

Read aloud missing persons story below. Fictional parents are looking for their children and need to figure out ways to find a match:

" Naomi and Gabriel lost their children about three years ago. The war in their village was devastating, their home and all their possessions were destroyed but nothing compared to the loss of their two children. Enemy troops invaded their village and during the conflict, their two children, Alex and Sophia went missing. Naomi and Gabriel managed to escape, but their two young children were captured. They searched and waited for three very long and tiring years traveling back to their village but there was no sign of them.

Recently, the local police have helped another couple find their children in a village about two hours away. Naomi and Gabriel were hopeful and hired the police’s best detective to travel with them to look for evidence. When they reached the village, the authorities told them they had found some adopted refugee children that came over about three years ago after the war. The children were quickly adopted and evidence suggests they were originally from Naomi and Gabriel’s village. The families who adopted them have been taking good care of them and love the children very much but Naomi and Gabriel want to find their children. They need the help of genetic experts, including you, to help identify their children from a group of ten adopted children.

Two methods of identifying children of specific parents are to look at their blood and DNA. By matching up blood types they can figure out which children are possible matches and which children cannot be matches. The couple also discusses trying to match their DNA fingerprints. They know that DNA needs to be extracted from the cells, cut and stained in a lab. This test is significantly more expensive that blood typing but can provide strong evidence in identification. It can be collected from the children’s blood, teeth or even hair. Your job is to investigate both methods in order to help identify these missing children."

Model how to figure each children's blood type at the blood typing station.

Make sure students are on the following website: http://www.biology.arizona.edu/human_bio/problem_sets/blood_types/btcalcA_popup.html
Type in parents blood types to then calculate the possible blood types for their children. Explain to students that they are to record the possible matches on their worksheet.

Model how to match the DNA fingerprints:

Show students how to match up bands of DNA. Each line of DNA should match to either the mother or the father (because offspring inherits half of their DNA from the mother and half from the father).

Note: Students may have difficulty matching up the bands of DNA. It's very important to explain that the children's DNA fingerprint must fit exactly in the dotted rectangular box in between the two parents’ DNA fingerprints. Line up the bottom of the rectangular strip. The part that says: Girl 1 is NOT part of the DNA fingerprint

Explain to students that the DNA should not match exactly to the mother or exactly to the father, or else they would look identical! Tell students to record the possible matches on their worksheet.

Split up the class into different groups depending on class size and as you see fit.
Students will rotate between two stations. (You may need to create two of each station, or 4 stations in total.) Follow the procedures at each station.
Have the students answer the following analysis questions based on their investigation:

According to your blood typing results, which children are likely to be Naomi and Gabriels?(Girl 2, Girl 3, Boy 6, Boy 8)
According to your blood typing results, which children are notlikely to be Naomi and Gabriels?(Girl 1, Girl 4, Boy 5, Boy 7)
According to your DNA fingerprinting results, which children are likely to be Naomi and Gabriels? (Girl 3, Boy 6)
According to your DNA fingerprinting results, which children are not likely to be Naomi and Gabriels? (Girl 1, Girl 2, Girl 4, Boy 5, Boy 7 Boy 8)
Which method helped you to better identify the missing children? (Blood Typing helped to narrow down the pool of children to four possibilities but the DNA fingerprint provided only one match)
What are some of the pros and cons of each method?

Share out answers to analysis questions
Explain Student Worksheet to either be done at home or in class if you want to more closely monitor student progress.

Extensions

Students can use a punnett square to figure out the allele combinations versus using the computer blood typing calculator. Previous practice and a clear understanding of punnett squares would be necessary.

Assessments and Rubrics

Please see Project Rubric.

Students will answer analysis questions in their lab notebooks.
Students will choose a method (DNA fingerprinting or Blood typing) and create an "all you need to know" pamphlet about their chosen method, listing the pros, cons, estimated costs, and effectiveness.
The pamphlet can be assigned as an at home project or a classwork assignment if you want to monitor student progress. A suggested rubric for the pamphlet is attached.

External Resources

Creating a DNA fingerprint interactive video: http://www.teachersdomain.org/resource/tdc02.sci.life.gen.creatednafingerprint/
DNA Fingerprint Photos: http://www.teachersdomain.org/resource/tdc02.sci.life.gen.dnafingerprints/
Forensic DNA Analysis Video: http://www.teachersdomain.org/resource/tdc02.sci.life.gen.sheppard/
Blood Typing Video: http://news.discovery.com/videos/why-tell-me-why-blood-types.html

Credits

SEPUP (Science Education For Public Understanding Program), Lawrence Hall of Science University of California: DNA Fingerprinting strips & story idea. Date accessed: 9/09
Learn. Genetics. Genetics Science Learning Center (http://learn.genetics.utah.edu/content/begin/traits/blood/): Background information. Date accessed: 4/8/11
The Office Website of the Nobel Prize (http://nobelprize.org/educational/medicine/landsteiner/readmore.html): Background information. Date accessed: 4/8/11
Thumbnail Image from googleimages.com. Website for this image at http://ww1.prweb.com/prfiles/2006/04/16/373208/AfghanRefugeeChildren.bmp. Date accessed: 4/9/11

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