Bacterial & Viral Genetic Systems

Question 1

Mechanisms of genetic exchange

Answer 1

Conjugation
Transformation
Transduction

Question 2

Bacteria usefullness

Answer 2

Small size
Rapid reproduction
Selective media that can easily identify the presence of an active allele
Simple structures and physiology
Genetic Variability

Question 3

Bacterial Virus

Answer 3

Known as bacteriophage, reproduce by infecting bacterial cells

They can grow in liquid or solid media

Question 4

Bacteriophage T4

Answer 4

Protein head

Genome contains 170,000 base pairs and 150 characterized genes

Large and complex genome

The phage goes through a lytic phase, meaning it lyses the cell to infect other cells.

Question 5

Bacteriophage Lamda

Answer 5

Genome contains 50,000 base pairs and 50 genes

May be lytic (lyses cells like T4) or lysogenic (inserts its DNA in the host cell genome and goes into latency)

Question 6

Lytic cycle

Answer 6

1. Attachment: The virus attaches to the surface of the host bacterium.
2. Penetration: The virus injects its genetic material into the host bacterium.
3. Replication: The viral genetic material takes over the host cell’s machinery, producing new viral particles.
4. Assembly: The new viral particles assemble into complete viruses.
5. Release: The host cell lyses, or breaks open, releasing the new viruses, which can then infect new host cells and start the cycle again.

Question 7

Lysogenic Cycle

Answer 7

1. Attachment: The virus attaches to the surface of the host bacterium.
2. Penetration: The virus injects its genetic material into the host bacterium.
3. Integration: The viral genetic material integrates into the bacterial chromosome, becoming a prophage.
4. Replication: The bacterial cell divides, and the viral genetic material is replicated along with the host DNA.
5. Lysogeny: The prophage remains dormant in the host DNA, not causing any harm to the host cell until it is triggered to enter the lytic cycle.

Question 8

Bacteria genetics

Answer 8

Bacterial genomes are circular molecules made out bacterial chromosomes (dsDNA, millions of base pairs)

Plasmids (small circular DNA )

Question 9

Plasmids

Answer 9

Small circular pieces of DNA that can replicate independently of the bacterial chromosome

They carry genes that provide benefits to the bacteria, such as antibiotic resistance

Question 10

Episomes

Answer 10

Large circular DNA that integrate into the bacterial chromosomes for replication or remain seperate

Question 10

Gene mutations

Answer 10

Can be observed via:

Colony colour and morphology

Nutritional mutants (can not metabolize certain sugars, like lactose or galactose)

Antibiotic resistance

Prototrophs and autotrophs (can not make certain amino acids, these need to be added to the growth medium)

Question 11

Conjugation

Answer 11

Direct transfer of DNA from one cell to another via the establishment of a cytoplasmic bridge

Cell contact required
Not sensitive to DNase

Question 12

Transformation

Answer 12

Transfer of a free (out of the cell) piece of DNA from one bacterium into another

Cell contact not required
Sensitive to DNase

Question 13

Transduction

Answer 13

Transfer of genes from one cell to another via bacteriophage (vector)

Cell contact not required
Not sensitive to DNase

Question 14

Prototrophs

Answer 14

Bacteria cells that are able to grow and reproduce in a minimal or basic medium that contains only the essential nutrients required for bacterial growth

Question 15

Auxotrophs

Answer 15

Bacteria with a genetic mutation that prevents them from being able to produce certain nutrients needed for grwoth and survival

They instead obtain their nutrients from their environment