Lecture 3 Answers - Lecture 3: Study Questions and Answers...

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Lecture 3 : Study Questions and Answers 1. Why was Mendel’s approach to the study of heredity so successful? Mendel was successful for several reasons. He chose to work with a plant, Pisum sativum , that was easy to cultivate, grew relatively rapidly, and produced many offspring whose phenotype was easy to determine, which allowed Mendel to detect mathematical ratios of progeny phenotypes. The seven characteristics he chose to study were also important because they exhibited only a few distinct phenotypes and did not show a range of variation. Finally, by looking at each trait separately and counting the numbers of the different phenotypes, Mendel adopted a reductionist experimental approach and appliesthe scientific method. From his observations, he proposed hypotheses that he was then able to test empirically. 2. What is the difference between genotype and phenotype? Genotype refers to the genes or the set of alleles found within an individual. Phenotype refers to the manifestation of a particular character or trait. 3. What is the principle of segregation? Why is it important? The principle of segregation, or Mendel’s first law, states that an organism possesses two alleles for any one particular trait and that these alleles separate during the formation of gametes. In other words, one allele goes into each gamete. The principle of segregation is important because it explains how the genotypic ratios in the haploid gametes are produced. 4. How are Mendel’s principles different from the concept of blending inheritance discussed in Chapter 1? Mendel’s principles assert that the genetic factors or alleles are discrete units that remain separate in an individual organism with a trait encoded by the dominant allele being the only one observed if two different alleles are present. According to Mendel’s principles, if an individual contains two different alleles, then the individual’s gametes could contain either of these two alleles (but not both). Blending inheritance proposes that offspring are the result of blended genetic material from the parent and the genetic factors are not discrete units. Once blended, the combined genetic material could not be separated from each other in future generations. 5. What is the concept of dominance? How does dominance differ from incomplete dominance? The concept of dominance states that when two different alleles are present in a genotype, only the dominant allele is expressed in the phenotype. Incomplete dominance occurs when different alleles are expressed in a heterozygous individual, and the resulting phenotype is intermediate to the phenotypes of the two homozygotes. 6. What are the addition and multiplication rules of probability and when should they be used?
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The addition and multiplication rules are two rules of probability used by geneticists to predict the ratios of offspring in genetic crosses. The multiplication rule allows
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This note was uploaded on 05/07/2011 for the course BIOLOGY 352 taught by Professor Townsend during the Spring '08 term at San Diego State.

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Lecture 3 Answers - Lecture 3: Study Questions and Answers...

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