Biology: Mechanisms of Genetic Transfer in Bacteria

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Questions and Answers

What was the purpose of the filter in the U-tube apparatus used by Bernard Davis?

To prevent the passage of genetic material

To allow the passage of genetic material, but prevent the passage of bacterial cells (correct)

To allow the passage of bacterial cells

To mix the two bacterial strains

What is a key difference between genetic transfer in bacteria and sexual reproduction in eukaryotes?

Genetic transfer in bacteria involves a combination of conjugation, transduction, and transformation (correct)

Genetic transfer in bacteria only involves conjugation

Genetic transfer in bacteria does not involve genetic recombination

Genetic transfer in bacteria does not enhance genetic diversity

What was the conclusion of Lederberg and Tatum's experiment?

The experiment did not provide conclusive evidence for genetic transfer (correct)

The met+ bio+ thr+ leu+ thi+ strain gained the ability to synthesize biotin and methionine

The met- bio- thr- leu- thi- strain gained the ability to synthesize threonine and leucine and thiamine

Both strains exchanged genetic material resulting in a new strain

What is the primary mechanism of genetic transfer in which bacteriophages are involved?

Transduction Signup and view all the answers

What is the primary requirement for the transfer of genetic material between bacterial cells?

Direct physical contact between cells Signup and view all the answers

What was the function of the U-tube apparatus used by Bernard Davis?

To test the requirement of direct physical contact for conjugation Signup and view all the answers

Why are crosses not used in the genetic analysis of bacterial species?

Because bacteria reproduce asexually via binary fission Signup and view all the answers

What is the term for the uptake of genetic material from the environment in bacteria?

Transformation Signup and view all the answers

What did the experiment by Lederberg and Tatum demonstrate?

The transfer of genetic material between bacterial cells Signup and view all the answers

What was the purpose of the experiment by Lederberg and Tatum?

To test the possibility of genetic material transfer between bacterial cells Signup and view all the answers

What is the purpose of Table 7.1 in the context of genetic transfer in bacteria?

To illustrate the three mechanisms of genetic transfer Signup and view all the answers

What is a characteristic of bacteria that affects their cellular traits?

Allelic differences between different strains of bacteria Signup and view all the answers

What is the primary mechanism by which a bacteriophage incorporates a fragment of bacterial chromosomal DNA into a newly made phage particle?

Through infection of a donor cell Signup and view all the answers

What is the term for bacterial cells that can synthesize all their necessary nutrients from the components in their growth medium?

Prototrophs Signup and view all the answers

What is the process by which a bacterial cell releases a fragment of its DNA into the environment, which is then taken up by a recipient cell?

Transformation Signup and view all the answers

What is the term for the circular segment of DNA transferred to a recipient cell during conjugation?

Plasmid Signup and view all the answers

What was the significance of the experiment conducted by Joshua Lederberg and Edward Tatum in 1946?

It discovered the process of genetic transfer in bacteria Signup and view all the answers

What is the process by which a recipient cell incorporates a fragment of DNA into its chromosome?

Recombination Signup and view all the answers

What was the purpose of applying pressure or suction in Davis's experiment?

To facilitate the movement of liquid through the filter Signup and view all the answers

What is the term used to describe the transfer of DNA from one bacterium to another following direct cell-to-cell contact?

Conjugation Signup and view all the answers

Which of the following strains of bacteria are capable of acting as donor cells in conjugation?

Only certain strains of bacteria Signup and view all the answers

What is the function of the genes named tra or trb followed by a capital letter?

They are involved in the transfer of DNA during conjugation Signup and view all the answers

What is the term used to describe the small circular piece of DNA found in certain donor strains of E. coli?

F factor Signup and view all the answers

What is the designation for strains of bacteria that lack an F factor?

F- Signup and view all the answers

What is the result of conjugation in a recipient cell?

It acquires an F factor Signup and view all the answers

What is the characteristic of episomes among plasmids?

They can integrate into a chromosome Signup and view all the answers

What is the primary function of fertility plasmids?

To allow conjugation Signup and view all the answers

What is the typical range of size of plasmids?

From a few thousand to 500,000 bp Signup and view all the answers

What is the primary advantage of plasmids to bacteria?

They can provide growth advantages Signup and view all the answers

How do plasmids replicate in bacteria?

They replicate independent of the bacterial chromosome Signup and view all the answers

Study Notes

Mechanisms of Genetic Transfer in Bacteria

There are three mechanisms of genetic transfer in bacteria: conjugation, transduction, and transformation
Conjugation involves direct physical contact between a donor and a recipient cell, and requires the presence of an F factor (fertility factor)
Conjugation can occur between different species of bacteria
The genotype of the bacterial cells that grew on the plates must be met bio thr leu thi
Lederberg and Tatum's experiment demonstrated genetic transfer between two strains of E. coli
The results of the experiment cannot distinguish between the two possibilities: either the met - bio - thr + leu + thi + strain gained the ability to synthesize biotin and methionine, or the met bio thr leu thi strain gained the ability to synthesize threonine and leucine and thiamine

Conjugation

Requires direct physical contact between a donor and a recipient cell
The F factor (fertility factor) is a small circular piece of DNA that carries genes required for conjugation
F+ cells can act as donor cells, while F- cells cannot
Genes involved in the transfer of DNA are named tra or trb followed by a capital letter
The result of conjugation is that the recipient cell has acquired an F factor, converting it from an F- to an F+ cell

Plasmids

Plasmids are extra-chromosomal DNA molecules found in bacteria and some eukaryotic species
They are usually circular, but some are linear
They range in size from a few thousand to 500,000 bp
Some plasmids, called episomes, can integrate into a chromosome
Plasmids have their own replication origin and can exist as single copy or up to 100 copies per cell
They are not required for survival, but can provide growth advantages to the bacteria
There are five different categories of plasmids: fertility plasmids, resistance plasmids, degradative plasmids, col-plasmids, and virulence plasmids

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Description

Learn about transduction, a mechanism of genetic transfer in bacteria where a bacteriophage incorporates a fragment of bacterial chromosomal DNA into a newly made phage particle.