1. For each pair of terms, explain how the meanings of the terms differ.
a. operator and operon b. proto-oncogene and oncogene c. intron and exon d. homeotic gene and homeobox
2. Explain the relationships between carcinogen and mutagen.
3. Use the following terms in the same sentence: gene, gene expression, regulator gene, and repressor protein.
4. Word Roots and Origins The word morphogenesis is derived from the Greek morphe, which means "shape," and the Latin genus, which means "birth." Using this information, explain why the term morphogenesis is a good name for the biological process that the term describes.
Understanding Key Concepts
5. Identify the term that describes the activation of a gene that results in transcription and the production of mRNA.
6. Name the kind of organism in which gene expression was first observed.
7. Describe how E. coli benefit by making enzymes to utilize lactose only when lactose is in the cellular environment.
8. Explain what causes the lac operon to "turn off" and "turn on."
9. Compare pre-mRNA with mRNA.
10. Describe the role of enhancers in the control of gene expression.
11. Evaluate the relationship between gene expression and morphogenesis.
12. Identify the role of homeoboxes in morphogenesis.
13. Compare the roles of proto-oncogenes and tumor-suppression genes.
14. State the unusual characteristic of cancer cells that can lead to metastasis.
15. Define carcinogen.
16. Unit 6—Gene Expression jF*^ Write a report describing the influ-
' £ ence of homeotic genes on an organism's development.
17. CONCEPT MAPPING Use the following □ □ □ terms to create a concept map that shows how a mutated gene can lead to cancer: exon, gene expression, intron, mutagen, oncogene, proto-oncogene, tumor-suppressor gene, and tumor.
18. Analyzing Information Kwashiorkor is a disease in children caused by a diet high in carbohydrates but lacking in complete protein. When children with kwashiorkor are put on a diet rich in protein, they may become very ill with ammonia poisoning, and some even die. The high level of ammonia in their blood is due to the inadequate metabolism of protein. What does this tell you about the enzymes that metabolize protein?
19. Relating Concepts Fruit flies of the genus Drosophila feed on fermenting fruit, which often contains a large amount of alcohol. If these fruit flies are fed a diet that has a high alcohol content, the amount of the enzyme that metabolizes alcohol in the digestive tract increases. What does this increase tell you about the enzyme?
20. Interpreting Graphics Study the diagram of the lac operon shown below.
a. Describe the role of the following elements shown in the diagram: promoter, operator, and structural genes.
b. What does it mean to say that an operon is "turned on"?
c. Is the operon "turned on" in the diagram shown below?
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