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How can DNA be used to determine if populations are isolated from one another?

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Download the files below to use offline, or to incorporate into your own lesson planning tools.

Popsicle DNA Activity slide

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Popsicle DNA Activity teacher's guide

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Colored Popsicle Sticks

ONLINE MEDIA

Popsicle DNA Activity slide

TEACHER'S GUIDE

Complete the following demonstration to show students how DNA can be used to determine whether populations are isolated from one another or whether or not they are able to breed with one another. (Note: You can use a Popsicle DNA Activity Slide (see Online Media above, or the Downloads sidebar) to use instead of popsicle sticks.)

Demonstration: How can DNA be used to determine if populations are isolated from one another?

Prepare: Set up four different populations of Popsicle sticks or M&Ms. Each population will have a different composition of colored Popsicle sticks or M&Ms, which represent different versions of genes (alleles).

Population A contains:

1) 15 blue sticks
2) 12 green sticks
3) 12 plain sticks

Population B contains:
1) 10 blue sticks
2) 15 green sticks 
3) 10 plain sticks

Population C contains:
1) 5 blue sticks
2) 15 green sticks
3) 19 plain sticks

Population D contains:
1) 1 blue stick
2) 2 green sticks
3) 26 plain sticks

Question:  Which populations breed the most frequently with one another? 
Answer: Population A breeds most frequently with B and C.

Question:  Which population appears to be the most isolated? Why?
Answer: Population D appears to be the most isolated because it has very few blue and green sticks (or versions of that gene). If individuals from population D bred more frequently with the other populations than the number of blue and green sticks would increase.

Extension

Use these online resources from the University of Utah’s Genetic Science Learning Center to give your students more background knowledge about DNA.

Have the students take this Tour of the Basics to get a visual explanation of DNA and how it operates in the cell:
Tour of the Basics
http://learn.genetics.utah.edu/content/begin/tour/

Then let them practice building a DNA molecule virtually:
Build a DNA Molecule
http://learn.genetics.utah.edu/content/begin/dna/builddna/

Extension

The scientists who discovered the structure of DNA in the 1950s would build models out of materials at hand, like paper or wooden beads, to try to better understand its structure.  Students can get a better understanding of DNA by building their own models.  A high school science teacher offers these materials and tips on building a paper model of the DNA molecule:
How to Make a Paper Model of DNA 
http://cavalierscience.blogspot.com/2007/04/how-to-make-paper-model-of-dna.html

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