Module 12: Study Guide Questions - Genetics PDF

**Module 12: Study Guide Questions** **Main Topic: Genetics** Hello Students! Below are the topics we've studied & questions you should practice answering in writing/aloud before the exam. A good system is to sort questions based on your current understanding of & comfort with related concepts. Ma...

**Module 12: Study Guide Questions** **Main Topic: Genetics** Hello Students! Below are the topics we've studied & questions you should practice answering in writing/aloud before the exam. A good system is to sort questions based on your current understanding of & comfort with related concepts. Mark questions with ✓ (got it!), **\~** (so-so), or **?**, then practice writing/talking out the questions starting with those you feel you understand (✓). Save the **?** questions for last; those will be more time-consuming. Some topics require you to simply memorize terms, but many topics require you to understand the concept. For more ideas and suggestions on studying biology, check out the "How to Study Biology" link in the Introductory Module. **Study Questions:** - **Define these terms: gene, allele, phenotype vs. genotype, homozygous, heterozygous, dominant allele, recessive allele.** - **What does it mean for an allele to be completely dominant? Give an example of a complete dominance inheritance pattern.** - **In genetics, what does it mean for someone to be a carrier?** - **Define incomplete dominance and illustrate an example** - **Define codominance and illustrate an example.** - **Identify examples and explain the genetics behind polygenic traits and continuous inheritance patterns.** - **Define continuous (monogenic) and discontinuous (polygenic) traits. Give an example of each kind.** - **Explain why depression is considered a multifactorial trait. Give examples of other traits that are multifactorial.** - **How do chromosomes determine sex, and how does sex influence the inheritance of certain traits?** - Why are males more effective with sex-linked diseases than females? - **What is a pedigree chart and how is it useful for understanding genetics?** **Part of *learning* genetics is *doing* genetics. Please continue to practice setting up Punnet squares to determine the probability of offspring inheriting the specified traits for the parents. These are the types of problems you may see on the exam so doing them will help you to prepare. A key will be posted at a later time but I encourage you to work through them on your own before looking at the key.** **Genetics and Inheritance Practice Problems** 1. **[Complete Dominance Crosses.]** For this example, use the following information: tall pea plants are dominant over short pea plants. For each scenario: show a Punnett Square & answer the questions. Two heterozygous tall pea plants are crossed. Use T = tall allele and t = short allele \% of homozygous dominant plants? \_\_\_\_\_\_ Phenotype?\_\_\_\_\_\_\_\_\_\_\_ \% of homozygous recessive plants? \_\_\_\_\_\_ Phenotype?\_\_\_\_\_\_\_\_\_\_\_ \% of heterozygous plants? \_\_\_\_\_\_ Phenotype?\_\_\_\_\_\_\_\_\_\_\_ Phenotypic Ratio (tall: short)? \_\_\_\_\_\_\_\_\_\_\_ 2. **[Complete Dominance Crosses]** In humans tongue rolling is dominant to non-tongue rolling. What would be the expected type of offspring if a homozygous tongue roller was crossed to a heterozygous tongue roller? Report the genotypes and phenotypes.  Genotype(s): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Phenotype(s): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 3. **[Complete Dominance Crosses]** In humans, earlobes are either "free" or "attached". The free earlobe trait is dominant over attached earlobes. a. Can a man and a woman, both with attached earlobes, have a child with free earlobes? Explain. b. Can a man and a woman, both with free earlobes, have children with attached earlobes? Explain.  4. **[Complete Dominance Crosses]** A widow's peak hairline is dominant to straight hairline. Cross two people who are heterozygous for a widow's peak hairline. What are the genotypes and phenotypes of the possible offspring? Genotype(s): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Phenotype(s): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 5. **[Incomplete Dominance.]** In the four o\'clock plant, the flowers may be red (R=dominant) or white (r=recessive) in the purebred form. But heterozygous plants have pink flowers. a\) The genotype for the following three plants: red flowered plants \_\_\_\_\_\_\_\_\_\_ pink flowered plants \_\_\_\_\_\_\_\_\_\_ white flowered plants \_\_\_\_\_\_\_\_\_\_ b\) Cross a pink and a red four o\'clock plant  Possible genotypes for each offspring: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Genotypic ratio (RR : Rr : rr)? \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Possible phenotypes for each offspring: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Phenotypic ratio (red : pink : white)? \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 6. **[Incomplete Dominance:]** Hair texture exhibits incomplete dominance. The dominant trait is straight hair and the recessive trait is curly hair, however heterozygous individuals have wavy hair (a phenotype *in between* that of the curly and straight haired individuals). What are the genotypes and phenotypes of the possible offspring when **two wavy haired** individuals mate? Genotype(s): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Phenotype(s): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 7. **[Codominance.]** Cattle which are homozygous for a red coat allele are red (RR), cattle which are homozygous for a white coat allele are white (WW), and heterozygous (RW) cattle appear roan (red hairs mixed with white) due to codominance of the red and white coat color alleles. a) A roan cow mates with a white bull, what will be the phenotypes of the offspring? **\ \_\_\_\_\_\_ % are \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ color** **\_\_\_\_\_\_ % are \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ color** **\_\_\_\_\_\_ % are \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ color** b\) What alleles are needed for the offspring of a mating to be Red? In the mating set up in Part a, **[explain]** whether or not Red offspring can be produced. 8. **[Blood alleles exhibit codominance.]** What is the probability that a parent with Type AB blood would have a child with Type O blood? Explain (you can use the Punnett square to help you derive the answer). 9. **[Sex (X) linked Crosses.]** In *Drosophila* (fruit fly), the gene for red eyes (R) is dominant to the gene for white eyes (r) and is X-linked. Determine the possible genotype and phenotype rations from expected from a cross between: a) Heterozygous female and Red-eyed male Genotypes for male offspring: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Phenotypes for male offspring (with %): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Genotypes for female offspring: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Phenotypes for female offspring (with %): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ b\) Homozygous dominant female and a Red-eyed male Genotypes for male offspring: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Phenotypes for male offspring (with %): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Genotypes for female offspring: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Phenotypes for female offspring (with %): \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 10. **Hemophilia is a recessive, X-linked trait.** a\) What is the probability that a man with hemophilia mating with a woman who is homozygous for the normal form of the blood clotting factor gene will have a son with hemophilia?  Probability: \_\_\_\_\_\_\_\_\_\_\_\_\_\_ b\) A man with the normal form of the blood clotting factor mates with a woman who is a carrier for hemophilia. What is the probability that their sons will have hemophilia? Their daughters? Probability of hemophilia (son): \_\_\_\_\_\_\_\_\_\_\_\_\_\_ Probability of hemophilia (daughter): \_\_\_\_\_\_\_\_\_\_\_\_\_\_