Chapter 7- Genetic transfer and mapping in bacteria

Question 1

What is genetic transfer?

Answer 1

It happens when segment of genetic DNA is transferred from one bacteria to another.

Question 2

What are the differences between gram positive and gram negative?

Answer 2

Gram positive has think layer of peptidoglycan. However, gram negative have think layer of peptidoglycan.

Question 3

What are phototrophs?

Answer 3

They are bacteria that can grow on minimal media. In another word, they can synthesize the essential nutrients that they need.

Question 4

What are autotrophs?

Answer 4

Bacteria that grow on complete media. They are bacteria that are unable to synthesize the essential nutrient that they need.

Question 5

What are the three ways of genetic transfer?

Answer 5

1. Transformation (involves uptake from the environment)
2. Transduction (involves bacteriophages)
3. conjugation (involves direct physical contact)

Question 6

What is plasmid?

Answer 6

It is extra chromosomal DNA.

Question 7

Are plasmid linear or circular?

Answer 7

Most plasmid are circular, however some are linear.

Question 8

What type of cell does plasmid exist in?

Answer 8

It is found in many bacteria and few Eukaryotic cells.

Question 9

Does plasmid replicate dependently or independently of host chromosomes?

Answer 9

It replicates independently.

Question 10

Are plasmid required for survival?

Answer 10

No, they are usually not required for survival but they provide growth advantages to the bacteria.

Question 11

What is Polylinker?

Answer 11

It is where scientist insert genes into plasmid.

Question 12

What does the arrow in plasmid diagram means?

Answer 12

They tell the direction of gene transcription.

Question 13

What does the boxed in plasmid diagram means?

Answer 13

They are direct nucleic acid sequences repeats.

Question 14

How does transformation process occur?

Answer 14

A bacterial cell dies releasing a fragment of its DNA into the environment. A recipient bacteria pick up the fragment and incorporate into its chromosomes by recombination.

Question 15

How does conjugation process occur?

Answer 15

A direct physical contact is needed. The donor cell transfer a segment of DNA to the recipient.

Question 16

How does transduction process occur?

Answer 16

A bacteriophage infect a donor cell. It incorporate a segment of bacterial DNA into a newly made phages. The phages then transfer the DNA fragment into the recipient cell, which incorporate the DNA into its chromosomes by recombination.

Question 17

How could bacteria become artificially competent?

Answer 17

1. electro-shock
2. chemical treatment
3. Heat shock

Question 18

How many crossover is needed to incorporate the new DNA fragment?

Answer 18

Two crossovers is needed to eventually replace the transformed DNA into the host chromosome.

Question 19

What are the laboratory method used for artificial transformation?

Answer 19

1. Calcium chloride + high temperature shock

2. Electroporation

Question 20

What is the mechanism steps of conjugation transfer?

Answer 20

1. Relaxosome recognize the origin of transfer and makes a cut in the DNA
2. Relaxosome, the most accessory point, releases relaxase
3. the relaxase proteins attaches to the end of the T DNA making a TDNA/ relaxase complex which get transferred to the exporter.
4. The coupling factor recognizes the complex
5. The exporter pump the complex from the donor cell through conjugation bridge to the recipient cell
6. In the donor cell, the F factor get replicated to become double stranded again.
7. In the recipient cell, the F factor also get replicated to become double stranded DNA.

Question 21

How is HFR cell is fromed?

Answer 21

It is formed when the F factor get integrated into the cell chromosome.

Question 22

What is bacteriophages composed of?

Answer 22

It is composed of genetic material surrounded by a protein coat.