Unit 6 Genetics Study Guide

Biology- Unit #6 –Genetics Name:__________________________ Period:_______ Essential Skills I. II. Recognize and define the terms genotype, phenotype, dominant, recessive, heterozygous and homozygous. Be able to show the expected phenotype and genotype ratios for any single trait Punnett Square cross. Study Guide 1. How do we represent a dominant allele? Recessive? 2. Using the letter “T” for the allele, write an example of homozygous dominant, homozygous recessive, and heterozygous individuals. 3. Explain how the following terms relate to each other: a. DNA – Chromosome b. Gene – Chromosome c. Gene – Trait d. Trait – Allele 4. What is the Law of Independent Assortment? 5. Draw a picture of Crossing-over. Using this picture, explain how an individual with blue eyes could have blonde or brown hair. 6. Explain the relationships between the following sets of terms: * Dominant vs. Recessive – * Genotype vs. Phenotype – * Homozygous vs. Heterozygous – * Purebred vs. Hybrid 7. How does genotype affect phenotype? Use the terms dominant, recessive, homozygous and heterozygous. 8. If short tails are dominant to long tails, what are the phenotypic and genotypic ratios of a cross between a dog with a long tail and a dog with a short tail (who had a parent with a long tail)? 9. If you had a short tailed dog and did not know the phenotypes of its parents, how could you conclusively determine the genotype of your dog? Explain using examples of a Test Cross. 10. Complete the following table that summarizes the 4 basic genetic crosses: (B=black; b =brown) Word Cross Genotype Cross BB x bb Offspring Genotype Ratio Offspring Phenotype Ratio Homozygous Dominant x Heterozygous 1 BB: 2 Bb: 1 bb 2 Black : 2 Brown 11. How are Incomplete Dominance and Co-dominance similar? How are they different from each other? Give examples of each type of inheritance. 12. Differentiate between a multiple allele trait versus a trait that is determined by incomplete dominance . Give examples of each type of inheritance. 13. Show the expected genotype and phenotype ratios of a cross between a man with type A blood and a woman with type B blood (both the man and woman had parents with type O blood). 14. What is the difference between Autosomes and Sex Chromosomes? What sex chromosomes determine male? Female? Why do sex-linked traits affect males more than females? 15. Show the expected genotype and phenotype ratios of a cross between a man who is colorblind and a woman who has normal vision (but her father was colorblind). 16. List 4 different environmental factors that can potentially affect the phenotype. 17. Describe the difference between “nature” and “nurture”. How do each potentially change the phenotype? 18. A woman has hemophilia (a recessive, sex-linked trait). What are the genotypes of her parents? Using a Punnett Square, show the cross that results in the woman inheriting hemophilia. 19. Pedigrees: a. Is this pedigree showing a dominant or recessive disorder? b. How do you know? c. Write all possible genotypes for individuals shown on the pedigree. 20. In a pedigree, what do the circles represent? Squares represent? What does it mean if a circle or square is completely shaded? What does it mean if it is only half-shaded? What if there is no shading?