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3-15-10 IN Explain the purpose of a punnett square. Create your own monohybrid cross.

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Presentation on theme: "3-15-10 IN Explain the purpose of a punnett square. Create your own monohybrid cross."— Presentation transcript:

1 IN Explain the purpose of a punnett square. Create your own monohybrid cross

2 Through Analysis questions OUT Study guide Look through your notes preparing for the test. Begin to think about questions to ask me.

3 1. Predict the possible phenotypes and genotypes of the offspring from a mating of two beagles. A heterozygous female with the dominant phenotype for droopy ears (D) mates with a male with recessive phenotype for upright ears (d).

4 Predictions: Phenotypes-- 50% droopy 50% upright Genotypes % Dd(heterozygous) 50% dd(homozygous) Dddd Dddd Dd d

5 2. Describe the role of a Punnett square in predicting the potential ratio of genotypes that may result from a particular cross.

6 3. Recall that crossing-over causes some genes on the same chromosome to assort independently. What relationship might you expect between the spacing of genes on the chromosome and their frequency of independent assortment?

7 4. Remember that the gene for eye color in fruit flies is linked to the X chromosome. Predict F 1 and F 2 results of a initial mating between a homozygous red-eyed female and a white-eyed male.

8 XRXrXRXr XRXrXRXr XRYXRYXRYXRY X R XrYXrY F1F1 Predictions: Genotypes: 100% males X R Y 100% females X R X r Phenotypes: males are Red-eyed females are red-eyed

9 XRXRXRXR XRXrXRXr XRYXRYXrYXrY X R X r XRYXRY F2F2 Predictions: Genotypes: If male, 50% X R Y 50% X r Y If female, 50% X R X R 50% X R X r Phenotypes: Females are red-eyed, 50% males are red-eyed, 50% males are white-eyed

10 5. Explain why males are more likely than females to display the phenotypes associated with X-linked recessive traits.

11 6. Use your knowledge of X-linked traits to explain the inheritance of hemophilia in the story A royal tragedy.

12 7. Consider how tall you are. How tall will you likely be when you are fully grown? How tall might you have been if you were raised in a very different situation? How do your genes and the environment interact to determine how tall you will be?


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