Skip to main content
Pearson+ LogoPearson+ Logo
Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 6 - Genetic Analysis and Mapping in Bacteria and BacteriophagesProblem 3b
Chapter 6, Problem 3b

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: How was it established that chromosome transfer was unidirectional?

Verified step by step guidance
1
Understand the biological context: In bacterial conjugation between F⁺ (donor) and F⁻ (recipient) cells, genetic material is transferred from one cell to another. The question focuses on how it was shown that this transfer occurs in one direction only—from the F⁺ donor to the F⁻ recipient.
Review the experimental design: Scientists mixed F⁺ and F⁻ bacteria and then separated the two populations after conjugation. They used genetic markers unique to each strain to track the movement of DNA.
Analyze the results: By checking which markers appeared in the recipient cells after mating, researchers observed that only donor markers were transferred to the recipient, and no recipient markers were found in the donor cells.
Interpret the findings: The absence of recipient markers in donor cells indicated that DNA transfer did not occur from F⁻ to F⁺ cells, establishing the unidirectional nature of chromosome transfer during conjugation.
Summarize the conclusion: The unidirectionality was confirmed by the selective presence of donor genetic material in recipients and the lack of reciprocal transfer, demonstrating that chromosome transfer proceeds only from F⁺ to F⁻ cells.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2m
Was this helpful?

Key Concepts

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

F⁺ and F⁻ Bacterial Mating

F⁺ bacteria contain the fertility factor (F plasmid) and can initiate conjugation by forming a pilus to connect with F⁻ bacteria, which lack the F plasmid. This mating allows genetic material transfer from F⁺ to F⁻ cells, enabling the study of gene transfer mechanisms.
Recommended video:
Guided course
08:52
F Factor and Hfr

Unidirectional Chromosome Transfer

In bacterial conjugation, DNA transfer occurs only from the F⁺ donor to the F⁻ recipient, not in reverse. This unidirectionality was demonstrated by tracking genetic markers and observing that only the recipient acquired donor genes, confirming the direction of transfer.
Recommended video:
Guided course
07:10
Chromosome Structure

Use of Genetic Markers to Trace DNA Transfer

Researchers used specific genetic markers on donor and recipient chromosomes to monitor gene movement during conjugation. By analyzing which markers appeared in the recipient after mating, they established the direction and extent of chromosome transfer.
Recommended video:
Guided course
07:11
Mapping with Markers
Related Practice
Textbook Question

In this chapter, we have focused on genetic systems present in bacteria and on the viruses that use bacteria as hosts (bacteriophages). In particular, we discussed mechanisms by which bacteria and their phages undergo genetic recombination, which allows geneticists to map bacterial and bacteriophage chromosomes. In the process, we found many opportunities to consider how this information was acquired. From the explanations given in the chapter, what answers would you propose to the following questions? How do we know that in bacteriophage T4 the rII locus is subdivided into two regions, or cistrons?

428
views
Textbook Question

Write a short summary that contrasts how recombination occurs in bacteria and bacteriophages.

695
views
Textbook Question

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: How was it established that physical contact between cells was necessary?

418
views
Textbook Question

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: What is the genetic basis for a bacterium's being F⁺.

602
views
Textbook Question

List all major differences between:

(a) The F⁺ x F⁻ and the Hfr x F⁻ bacterial crosses

(b) The F⁺, F⁻, Hfr, and F' bacteria.

901
views
Textbook Question

Describe the basis for chromosome mapping in the Hfr x F⁻ crosses.

1066
views