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USING GENETIC CROSSES TO ANALYZE A STICKLEBACK TRAITINTRODUCTIONGeneticists breed organisms with different characteristics, or phenotypes, to answer questionsabout how the phenotypes are inherited. Is one phenotype dominant and one recessive? Is eachphenotype controlled by a different version (allele) of a single gene, or are many interactinggenes involved? In this activity, you will answer these questions by analyzing the outcome ofbreeding a stickleback with pelvic spines and one without pelvic spines—the same procedure,called a genetic cross, that Dr. David Kingsley described in the film Evolving Switches, EvolvingBodies.The fish shown in the photo on the left is amarine threespine stickleback. Like allmarine and sea-run stickleback, this fish hasa pair of pelvic spines (only one is visible inthe photo), which serve as a defense fromlarge predatory fish. In some freshwaterpopulations, such as in Bear Paw Lake,Alaska, stickleback lack pelvic spines. (Thescale is in centimeters.)Guiding question: How are these two phenotypes inherited?MATERIALSYou will need:• F1 stickleback fish cards• F2 stickleback fish cards• CalculatorPROCEDUREWatch the short film entitled The Making of the Fittest: Evolving Switches, Evolving Bodies and then proceed througheach part of this activity as instructed by your teacher. Are pelvic spines dominant or recessive in stickleback fish?The dominant allele of the stickleback fish is producing a pelvic spine because when there is a change in the environment, stickleback fish with pelvic spines accumulate in higher frequencies This information was gathered from the video, “Making of the Fittest: Evolution of the Stickleback Fish - HHMI Biointeractive ...
Why do you think stickleback fish with a Pitx1 mutation are able to survive but not the mice?c) Why do you think stickleback fish with a Pitx1 mutation are able to survive but not the mice? By knocking out the protein-coding region of the Pitx1 gene in mice, the gene can no longer be expressed in any cells of the organism. The Pitx1 protein is critical for the normal development of the pituitary gland and jaw.
How do pelvic spines and other spines protect ocean stickleback fish?in the form of bony plates and spines projecting from the back and pelvis. When threatened, a stickleback can simultaneously flare out its pair of pelvic spines and three dorsal spines, making it difficult for predators to swallow them.
Which one of the three pelvic girdle phenotypes is analyzed in more detail in this experiment?The reduced pelvis phenotype is analyzed in more detail in this experiment.
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What would be the ratio of stickleback with pelvic spines to stickleback without spines in the F2 generation?
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