Gene Combo

Gene Combo - 2-28-13 Key Question: How do genes determine a trait? What happens to the parent’s gene that doesn’t show? Initial thoughts:

Evidence: Poppy & Skye Generation 1: Skye (blue tail) Poppy (orange tail) TT tt Homozygous = 2 copies of the same gene Blue, or T, is dominant over Orange, or little t. Little t is recessive. What is Skye’s phenotype? What is Skye’s genotype?

Generation 2 (Skye & Poppy’s Offspring) Ocean Lucy Tt Tt Heterozygous = 2 different genes What is their genotype? What is the phenotype?

Evidence 2: Coin Toss Model Paste the chart into your notebook Use the coin to represent whether Ocean & Lucy’s offspring get T or t. Heads = T Tails = t Remember: TT = blue tT or Tt = blue tt = orange

Graph your results

Analysis Questions What is the ratio of blue-tailed to orange-tailed critter pups? Ration = Number of blue tailed offspring Number of orange-tailed offspring Round this to the nearest whole number. Then express as a ration by writing it like this: _______ : 1 Express this ration as a pair of fractions, so that you can use them to complete the following sentence: “About _____ of the offspring have blue tails, and about _____ of the offspring have orange tails.” Why isn’t the ration 1:1 or half blue half orange?

Analysis Questions contd… You and your partner are about to toss 2 coins 100 times. Predict how many times the outcome would be: Heads-heads Heads-tails Tails-heads Tails-tails Look back at the Creature Features lesson. Do the results of the coin tossing model match the Generation Three critter data? Explain.

Summary What did you think about how genes determine a trait before? What did you learn from your evidence about how genes determine a trait? What are some further thoughts or questions you have about how genes determine a trait?

Reflection Write a letter to the Zoo explaining your findings about tail color traits and their chances.

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