more Punnett Squares
Punnett Squares and Probability:
Background:
Gregor Mendel used mathematical analysis of garden pea plants to develop the laws of genetics. In this lab, you will copy his experiments by studying a trait carried on human chromosomes. Remember, each sperm and egg cell carries only one gene for a trait, so when these cells fuse during fertilization, the result is a fertilized egg with two genes for the trait, one from each parent.
How the chromosomes separate from their partner during meiosis is random. So, we don’t know which allele that gamete (egg or sperm) is carrying for a specific trait. And, we don’t know which pair of alleles an offspring will inherit.
But, if we use what genetic information we do know about an offspring’s parents, we can use the principles of heredity to determine the offspring’s probable genotype by using Punnett Squares.
In this investigation you will examine chance genetic events to determine the probability of specific outcomes.
Prediction:
In a human almond–shaped eyes (E) are dominant to round-shaped eyes (e). What are the possible genotypes and phenotypes in the offspring if you cross two heterozygous parents? (Hint, do a Punnett square!)
Genotypes (Include the probability ratio):
Phenotypes (Include the probability ratio):
Objective: The purpose of this lab is to see how accurate a Punnett square is in predicting the probability of an offspring’s outcomes.
Materials: (per lab group)
20 yellow chips 20 red chips Two plastic cups or containers
Procedure:
1. Label one container “Dad (male)” and one container “Mom (female)”.
2. Count out 10 yellow chips for each cup and 10 red chips for each cup. (Each cup should now have a mixture of both colors. Shake each container to make sure the chips are evenly mixed up.
What is the genotype for the Dad? _______________________________
What is the genotype for the Mom? ______________________________
3. Gently shake each cup, have one person close their eyes and select ONE chip from the Dad cup. Have another person do the same for the Mom cup.
In this activity, there will be two possible phenotypes for eye shape:
1. E = almond-shaped eyes (represented by the red chip )
2. e = round-shaped eyes (represented by the yellow chip)
(HINT: both parents are heterozygous, have a mix of red and yellow chips)
4. After one chip has been selected from each cup, place a check in the data table in the correct column of the genotype selected. (Ex. If you and your partner each chose a red chip from each cup, you would check EE box for the first trial, a red and yellow chip means you would check the Ee box, and two yellow chips means you would check the ee box.)
5. Return the selected chip to the cup you took it from.
6. Continue selecting one chip from each container and recording your selections in your data table until you have complete 25 trials.
Results:
Background:
Gregor Mendel used mathematical analysis of garden pea plants to develop the laws of genetics. In this lab, you will copy his experiments by studying a trait carried on human chromosomes. Remember, each sperm and egg cell carries only one gene for a trait, so when these cells fuse during fertilization, the result is a fertilized egg with two genes for the trait, one from each parent.
How the chromosomes separate from their partner during meiosis is random. So, we don’t know which allele that gamete (egg or sperm) is carrying for a specific trait. And, we don’t know which pair of alleles an offspring will inherit.
But, if we use what genetic information we do know about an offspring’s parents, we can use the principles of heredity to determine the offspring’s probable genotype by using Punnett Squares.
In this investigation you will examine chance genetic events to determine the probability of specific outcomes.
Prediction:
In a human almond–shaped eyes (E) are dominant to round-shaped eyes (e). What are the possible genotypes and phenotypes in the offspring if you cross two heterozygous parents? (Hint, do a Punnett square!)
Genotypes (Include the probability ratio):
Phenotypes (Include the probability ratio):
Objective: The purpose of this lab is to see how accurate a Punnett square is in predicting the probability of an offspring’s outcomes.
Materials: (per lab group)
20 yellow chips 20 red chips Two plastic cups or containers
Procedure:
1. Label one container “Dad (male)” and one container “Mom (female)”.
2. Count out 10 yellow chips for each cup and 10 red chips for each cup. (Each cup should now have a mixture of both colors. Shake each container to make sure the chips are evenly mixed up.
What is the genotype for the Dad? _______________________________
What is the genotype for the Mom? ______________________________
3. Gently shake each cup, have one person close their eyes and select ONE chip from the Dad cup. Have another person do the same for the Mom cup.
In this activity, there will be two possible phenotypes for eye shape:
1. E = almond-shaped eyes (represented by the red chip )
2. e = round-shaped eyes (represented by the yellow chip)
(HINT: both parents are heterozygous, have a mix of red and yellow chips)
4. After one chip has been selected from each cup, place a check in the data table in the correct column of the genotype selected. (Ex. If you and your partner each chose a red chip from each cup, you would check EE box for the first trial, a red and yellow chip means you would check the Ee box, and two yellow chips means you would check the ee box.)
5. Return the selected chip to the cup you took it from.
6. Continue selecting one chip from each container and recording your selections in your data table until you have complete 25 trials.
Results:
Conclusion (Analysis):
1. Why is it important to conduct a large number of trials in an experiment?
2. Look at the genotypic ratio from your Punnett square cross. These are the THEORETICAL PROBABILITIES. Compare these predicted outcomes to the EXPERIMENTAL PROBABILITIES from your class data table. Are the numbers the same? Why or Why not?
1. Why is it important to conduct a large number of trials in an experiment?
2. Look at the genotypic ratio from your Punnett square cross. These are the THEORETICAL PROBABILITIES. Compare these predicted outcomes to the EXPERIMENTAL PROBABILITIES from your class data table. Are the numbers the same? Why or Why not?
Finish Early?
1) Try this PLIX on Punnett squares! Fill in the Punnett Square, and then try the Challenge Me! for probability questions.
2) Just for fun, try this online lab with Punnett Squares. What kind of creature can you create?
1) Try this PLIX on Punnett squares! Fill in the Punnett Square, and then try the Challenge Me! for probability questions.
2) Just for fun, try this online lab with Punnett Squares. What kind of creature can you create?
Class Punnett Square Practice:
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Punnett Square Practice Worksheet:
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Need more help with Punnett Squares?
Drag and Drop Punnett Squares
Need practice setting them up? Try these: You'll work these out on your own paper.
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And, here's more Punnett Squares:
Drag and Drop Punnett Squares
Need practice setting them up? Try these: You'll work these out on your own paper.
Or you can try these:
And, here's more Punnett Squares: