Concept explainers
Chlamydomonas, a eukaryoric green alga, may be sensitive to the antibiotic erythromycin, which inhibits protein synthesis in bacteria. There are two mating types in this alga, mt+ and mt–. If an mt+ cell sensitive to the antibiotic is crossed with an mt– cell that is resistant, all progeny cells are sensitive. The reciprocal cross (mt+ resistant and mt– sensitive) yields all resistant progeny cells. Assuming that the mutation for resistance is in the chloroplast DNA, what can you conclude from the results of these crosses?
To determine: The conclusion that can be drawn from the results of the given crosses.
Introduction: Chlamydomonas is a eukaryotic green alga and shows two mating types mt+ and mt-. The cross between mt+ cell (sensitive to antibiotic) and mt- cell (resistant to antibiotic) produces sensitive progeny cells.
Explanation of Solution
The following conclusions can be drawn from the results of the given crosses:
- The mt+ strain of Chlamydomonas is the donor of the chloroplast DNA. This is because the inheritance of resistance or sensitivity to the antibiotic relies on the status of mt+ gene.
- In Chlamydomonas, the chloroplasts obtain their features from mt+, whereas mitochondria obtain their features from the mt- strain.
Thus, mt+ strain is the donor of chloroplast DNA and the chloroplasts gain their characteristics from mt+. The mitochondria obtain their features from mt-.
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Chapter 9 Solutions
Concepts of Genetics (12th Edition)
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