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Name ________________________________ Class _______ Date _________________ Canine Coat Color Use the virtual Genetics lab room to determine the pattern of inheritance of coat color in Labrador retrievers. Lab Bench Used In Labrador retrievers, or Labs, coat color is a polygenic trait. This means that more than one gene determines the color of a Lab’s fur. A Lab can have black or brown coat pigments, or it can have no fur pigment, which causes the fur to appear yellow. In this virtual genetics lab activity, you will run different crosses to determine the pattern of inheritance of this polygenic trait. Enter the Virtual Bio Lab and select the title of this lab activity from the “Heredity” menu on the whiteboard. You will be taken to the virtual Genetics lab room. Part A: A Polygenic Trait Select “Dog, Domestic” from the Species Selector. Select “Coat Color” as the trait you will study. Look at your options in the “Set Alleles” box. Notice that this trait is determined by alleles two different loci (plural of locus), or locations on the chromosome. Coat color is therefore a polygenic trait. 1. What are the different allele possibilities for each of the two loci? ________________________________________________________ ________________________________________________________ Before determining dominant-recessive relationships of each set of alleles, test to see whether one locus is dominant over the other. To test the dominance between the two loci, cross the parents using their default genotype settings—both parents are homozygous for black coat and no pigment. Cross the parents enough times to produce 50 puppies. 2. What color puppies do these parents (both homozygous for black coat and no pigment) produce? What do these results tell you? ________________________________________________________ ________________________________________________________ ________________________________________________________ Reset the lab and set up a new cross. This time, set the female’s Locus 2 alleles to be heterozygous (one allele for “Pigment” and one for “No pigment.”) Set Locus 1 to be homozygous black for both the male and female. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 1 Heredity: Canine Coat Color Name ________________________________ Class _______ Date _________________ 3. What happens when you cross these parents? What do these results suggest about the inheritance pattern of the Locus 2 alleles? Explain your reasoning. ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ 4. Roll over the names of the two parents in the “Results” box. How do their phenotypes make sense in light of their genotypes and the inheritance pattern of the “Pigment” and “No pigment” alleles? ________________________________________________________ ________________________________________________________ ________________________________________________________ Part B: Black vs. Brown Reset the lab. Set up a cross to determine how the Locus 1 alleles (black vs. brown) interact. First, set both parents’ Locus 2 alleles as homozygous for pigment. It is up to you to decide how to set the Locus 1 alleles so you will find which one, if any, is dominant and which is recessive. 5. Describe your crosses and findings. ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 2 Heredity: Canine Coat Color Name ________________________________ Class _______ Date _________________ 6. Fill in the Punnett square below to show the results of a cross between a yellow female and a brown male that is heterozygous for pigment. Set the parental genotypes using P and p for the Locus 2 alleles. What percentage of the yellow female's puppies would share her yellow coat color? Yellow Female Brown Male 7. Why wasn’t it necessary to build a 16-cell Punnett square to answer Question 6? ________________________________________________________ ________________________________________________________ ________________________________________________________ 8. If both parents are heterozygous in both of the loci that are involved in coat color, what coat colors should be expressed in a very large litter of puppies? Explain your reasoning. ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ 9. Run the cross as described in Question 8 to see if the results match your prediction. Describe your results. ________________________________________________________ ________________________________________________________ ________________________________________________________ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 3 Heredity: Canine Coat Color Name ________________________________ Class _______ Date _________________ 10. Think about the pair of dogs you just crossed. Given their appearance and the offspring they produced, why might breeding Labrador retrievers be more challenging than some people imagine? How does knowing the parents’ genotypes make it easier? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ Part C: Breeding Dogs Imagine you are a dog breeder. You have a female black Lab that was produced by a brown mother and an unknown father. You want to find a mate for your dog so she'll produce brown puppies. What genotype would you need her mate to have in order to guarantee that some of the puppies will be brown? Work through the following questions to find the answer. Experiment within the virtual Genetics lab to help figure out the answers. 11. For the Locus 1 gene, what is the genotype of your black dog? How do you know? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 12. Did your dog's father have a black coat? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 13. To have the best chance of producing brown puppies, what is the ideal phenotype of your dog's potential mate? Explain. ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 4 Heredity: Canine Coat Color Name ________________________________ Class _______ Date _________________ 14. Is there any chance that some of your dog's offspring will be yellow? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 15. If your dog is heterozygous for both genes, and she mates with a brown male, at minimum, what percentage of her puppies should you expect to be brown? What about at maximum? Explain. ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Virtual Bio Lab 5 Heredity: Canine Coat Color