Chapter 9, Problem 1PDQ

HOW DO WE KNOW? In this chapter, we focused on extranuclear inheritance and how traits can be determined by genetic information contained in mitochondria and chloroplasts, and we discussed how expression of maternal genotypes can affect the phenotype of an organism. At the same time, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions?

1. (a) How was it established that particular phenotypes are inherited as a result of genetic information present in the chloroplast rather than in the nucleus?
2. (b) How did the discovery of three categories of petite mutations in yeast lead researchers to postulate extranuclear inheritance of colony size?
3. (c) What observations support the endosymbiotic theory?
4. (d) What key observations in crosses between dextrally and sinistrally coiled snails support the explanation that this phenotype is the result of maternal-effect inheritance?
5. (e) What findings demonstrate a maternal effect as the basis of a mode of inheritance?