Biology | Answers to Review Questions

Author Dr. George B. Johnson, Washington University
Author Dr. Peter H. Raven, Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer, Carleton College
Contributor Dr. Jonathan Losos, Washington University

Answers to Review Questions

Chapter 43 (p. 872)

1. Highly repetitive DNA sequences may be generated by amplification resulting from multiple rounds of DNA replication of a specific chromosome region. They could also result from the action of transposable elements.

2. Arabidopsis has an unusually small genome and only 20% repetitive DNA. Rice has a much smaller genome than other grains and is an important food source worldwide.

3. The availability of DNA microarrays, filled with many DNA sequences, to a wide number of scientists will make assaying the presence of a particular gene easier for more scientists.

4. With the knowledge of the genome of Arabidopsis and rice, emphasis may now be switched to proteomics. Proteomics deals with protein production and modification. From this study, one can learn what gene produces what protein and how similar genes in other plants are used to create biochemically and morphologically distinct organisms.

5. One can produce complete plants by organogenesis by using calluses obtained from callus culture. The callus is transferred to a medium containing appropriate hormones. Here it will complete the development into an entire plant. Somatic cell organogenesis utilizes a dispersion of callus cells in a liquid medium, producing a cell suspension culture. A portion of the cell suspension culture is transferred to a medium containing hormones that cause differentiation and organization, and an embryo is formed.

6. Plant protoplasts are produced by removing the cell walls enzymatically. Protoplasts can be forced together in a process called protoplast fusion, to form a hybrid that could not occur in nature. The hybrid protoplast is grown into a complete plant.

7. Microscopic gold particles are coated with DNA and accelerated with a particle gun to a high enough velocity to penetrate the cell wall of a plant cell. Plant transformation can also be done by electroporation. In this process, protoplasts are placed in a solution containing the desired DNA and shocked with high voltage electricity. DNA enters when the electricity opens pores temporarily. This technique requires the use of protoplasts free of their cell wall.

8. Genes coding for an antigen of a particular disease can be introduced into the genome of an edible plant. A human ingesting the plant would develop antibodies to the disease.