This activity is designed as a tutorial to enhance learning through multimedia and technological outlets.

1. Fair Use This presentation has been prepared under fair use exemption of the U.S. CopyrightLaw and is restricted from further use other than for educational purposes.

2. How to Complete a Punnett Square Matthew F Poston

3. What is a Punnett Square? The Punnett square method, named after R.C. Punnett is a convenient way to predict the genotypes and phenotypes of offspring. The Punnett square allows you to determine all the types of genetically different gametes that can be produced by the male and female parents.

4. Punnett Square To the right you will notice a Punnett square that will help you determine the outcome of a single-trait cross.

5. So how does one complete a Punnett square? First, you would need to find out which alleles are dominant and recessive. You can do this by looking at the chart provided in this mini-lesson. Lets say we wanted to figure out if a gamete is going to have dimples. Dimples are dominant over no dimples. Lets assign the dominant allele (dimples) the capital letter D and the recessive allele (no dimples) the lowercase d.

6. Dominant and recessive trait chartCharacteristics in the left-hand column dominate over those listed in the right-hand column Dominant traits browneyes farsightedness normal vision normal vision normal vision dark hair curly hair widow's peak dimples unattached earlobes broad lips double-jointedness short digits immunity to poison ivy normal pigmented skin normal blood clotting normal hearing Recessive Traits grey, green, hazel, blue eyes normal vision nearsightedness night blindness color blindness* blonde, light, red hair straight hair normal hairline no dimples attached earlobes thin lips normal joints normal digits susceptibility to poison ivy albinism hemophilia* congenital deafness * sex-linked characteristic

7. Completing the Punnett square Lets say we have a mother who is homozygous recessive (dd) for the trait. dd meaning not having dimples. We also have the father who is heterozygous (Dd) for the trait. Dd meaning he has dimples but also carries the recessive trait (d). The recessive trait could possibly be the allele he passes to his offspring.

8. Drawing and completing the Punnett square D d d d d d D d d d D d When the narrator prompts you to click, please left click your mouse once or hit the <enter> key once.

9. Outcomes Genotypes The possible genotypes are Dd and dd. There is a 50% chance that the offspring will have dimples and be a carrier of the recessive trait from the genotype Dd. There is also a 50% chance that the offspring will not have dimples and carry both alleles for not having dimples from the genotype dd. Phenotypes The offspring will have a 50% chance of displaying the physical characteristic of having dimples and 50% of displaying the physical characteristic of no dimples.

10. Bibliography Graphics http://www.biologyjunction.com/genetic_traits_activity.htm http://www.miracosta.edu/home/mspring/Project%20example.htm Data http://www.blinn.edu/socialscience/LDThomas/Feldman/Handouts/0203hand.htm Narration Shellie Marie Poston is in the 6th grade at Southeastern Middle School in Walnut Cove, NC.