Comprehension Questions

* 1. Briefly describe the general structures of mtDNA and cpDNA. How are they similar? How do they differ? How do their structures compare with the structures of eubacterial and eukaryotic (nuclear) DNA.

2. Explain why many traits encoded by mtDNA and cpDNA exhibit considerable variation in their expression, even among members of the same family.

* 3. What is the endosymbiotic theory? How does it help to explain some of the characteristics of mitochondria and chloroplasts?

4. What evidence supports the endosymbiotic theory?

5. How are genes organized in the mitochondrial genome? How does this organization differ between ancestral and derived mitochondrial genomes?

* 6. What are nonuniversal codons? Where are they found?

7. How does replication of mtDNA differ from replication of nuclear DNA in eukaryotic cells.

* 8. The human mitochondrial genome encodes only 22 tRNAs, whereas at least 32 tRNAs are required for cytoplasmic translation. Why are fewer tRNAs needed in mitochondria?

9. What are some possible explanations for an accelerated rate of evolution in the sequences of vertebrate mtDNA. *10. Briefly describe the organization of genes on the chloroplast genome.

11. What is meant by the term "promiscuous DNA"?

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