Viruses and Bacteria

Question 1

Why is it important to learn about viruses and bacteria?

Answer 1

• ability to harness these organisms it the key to our current ability to manipulate DNA

Question 2

How do viruses work?

Answer 2

• set of instructions, encoded by viral DNA, tells cell to stop functioning and to make more virus

Question 3

How did viruses use to be classified, and how are they classified now?

Answer 3

• Initially: viruses were classified by their host specificity and pathology of of disease they caused
• now: classified by nucleic acid they used, RNA or DNA (and single or double stranded)

Question 4

What are virions? And what do animals have?

Answer 4

• Virus particles
• Typically consist of simple protein coat or capsid and nucleic acid
• animals have addition of lipid bilayer

Question 5

What is a phage and what are two types?

Answer 5

• Phage = virus that infects and replicates within bacteria and archae
• Virulent phage - lytic reproductive cycle
• Temperate phage - lysogenic cycle

Question 6

What are retroviruses?

Answer 6

• special class of viruses

- bend rules of central dogma by making DNA copy from RNA genome

Question 7

What is specialized transduction?

Answer 7

• when prophage excises itself from chromosome, it can be sloppy and pick up a gene from bacterial chromosome
• that gene becomes part of virus genome and inserts into another bacteria when infected by that phage

Question 8

What is generalized transduction?

Answer 8

• instead of packaging phage DNA into virions, package chunks of bacterial chromosomes

Question 9

What is transformation?

Answer 9

• Bacteria can sometimes take up naked DNA floating in their environment
• Non-genomic DNA (plasmids) are used to transform the DNA

Question 10

What are R-factors?

Answer 10

• plasmids that carry antibiotic resistance genes

Question 11

What is conjugation?

Answer 11

• most sex-like way that bacteria exchange DNA
  1) conjugation occurs more frequently
  2) DNA takes some chromosomal DNA w/ it during conjugation
  3) the transferred DNA can be incorporated into chromosome F-cell by recombination
  IF U INTERUPT at diff times, you can see order of chromosomal genes and map them

Question 12

What is the unit of regulated transcription and the advantages of repressor?

Answer 12

• Unit: operon
• advantages:
  1) repressor only needs to be expressed at very low level
  2) regulates several inducible proteins
• trp operon is end product of tryptophan synthesis

Question 13

What is tryptophan?

Answer 13

• acts as co-repressor by binding/activating DNA binding conformating of repressor protein
• blocks transcription
• amino acid