Viruses and Bacteria

Question 1

Why study bacteria and viruses?

Answer 1

Bacteria and viruses have same genetic code as humans, but are much easier to manipulate

Question 2

What does a virus do?

Answer 2

Viruses are able to encode a set of instructions that tell the cell to halt its regular function and start reproducing more of the virus

Question 3

What is the name for a virus particle? How might it be different in an animal virus?

Answer 3

• A virus particle is called a virion

- Animal viruses often have a lipid bilayer

Question 4

How can viruses be separated into two categories?

Answer 4

• Viruses that infect bacteria (bacteriophage)

- Viruses that infect eukaryotes

Question 5

What are two types of cycles a virus can go through when infecting bacteria? explain them

Answer 5

• The lytic cycle is when a phage binds to bacteria and injects its DNA. Bacteria immediately reproduce the virus. When the cell has been used up, it open and releases more phage
• The lysogenic cycle has a phage inject DNA into the bacterial chromosome- becomes a part of it. The virus is then reproduced when bacteria undergoes division

Question 6

Which phage undergoes which viral cycle?

Answer 6

• A temperate phage undergoes the lysogenic cycle

- A Virulent phage undergoes the lytic cycle

Question 7

Can more than one phage enter the same bacterium?

Answer 7

Yes

Question 8

Two ways viruses infect eukaryotes

Answer 8

• Recombine and make copies (like lytic phage)

- Retrovirus: (RNA is inserted into DNA, changing the genome)

Question 9

How do prokaryotes divide?

Answer 9

• Similar to mitosis but simpler because bacteria have 1 circular chromosome

Question 10

What are the ways bacteria exchange genetic material?

Answer 10

• Specialized transduction: when phage accidentally picks up a gene from bacteria when it leaves chromosome. This is then inserted into next bacteria
• Generalized Transduction: phage accidentally packages bacteria and is injected into next chromosome
• Transformation: Bacteria take up naked DNA floating in environment
• Strand from one bacteria is donated to another

Question 11

How are genes in bacteria regulated?

Answer 11

Bacteria are able to regulate the transcription of their genes.
They have inducible enzymes: turn on and off as needed

Question 12

How do inducible enzymes work?

Answer 12

a “repressor” binds to a specific DNA sequence between promoter and start point- BLOCKS TRANSCRIPTION

Question 13

What are R-factors?

Answer 13

Plasmids that carry antibiotic resistant genes