Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

3. Energy & Cell Processes

Steps of Transcription

Anatomy & Physiology

3. Energy & Cell Processes

Steps of Transcription

Previous problemNext problem

Problem 7

Textbook Question

In a particular bacterial species, temperature-sensitive conditional mutations cause expression of a wild-type phenotype at one growth temperature and a mutant phenotype at another—typically higher—temperature. Imagine that when a bacterial cell carrying such a mutation is shifted from low to high growth temperatures, RNA polymerases in the process of elongation complete transcription normally, but no new transcripts can be started. The mutation in this strain most likely affects:a. the terminator sequenceb. the start codonc. sigmad. one of the polypeptides of the core RNA polymerase

Verified step by step guidance

Identify the role of each option in the transcription process: the terminator sequence, start codon, sigma factor, and core RNA polymerase.

Understand that the terminator sequence is involved in ending transcription, not starting it, so it is unlikely to be affected if elongation continues normally.

Recognize that the start codon is part of the translation process, not transcription initiation, so it is not relevant to the problem.

Recall that the sigma factor is responsible for the initiation of transcription by helping RNA polymerase bind to the promoter region of DNA.

Consider that if elongation continues but new transcription cannot start, the mutation likely affects the sigma factor, which is crucial for initiating transcription.

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Temperature-sensitive mutations

Temperature-sensitive mutations are genetic alterations that result in a phenotype that is dependent on the environmental temperature. At a permissive temperature, the organism exhibits a wild-type phenotype, while at a restrictive temperature, the mutation leads to a different, often non-functional phenotype. This concept is crucial for understanding how environmental factors can influence gene expression and protein function.

RNA polymerase function

RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template during transcription. It has distinct phases: initiation, elongation, and termination. In the context of the question, the ability of RNA polymerase to elongate existing transcripts but not initiate new ones suggests a disruption in the initiation phase, which is often regulated by factors such as sigma factors or promoter sequences.

Sigma factors

Sigma factors are proteins that bind to RNA polymerase and direct it to specific promoter regions on the DNA, facilitating the initiation of transcription. They play a critical role in recognizing the correct start sites for transcription. A mutation affecting sigma factors could lead to the inability to initiate new transcripts, which aligns with the scenario described in the question where elongation occurs but initiation does not.