Lecture 31

Question 1

What are viruses

Answer 1

Acellular microorganisms - cannot survive without host cell
rely on biosynthetic machinery of the host cell to multiply
infect all types of cell

Question 2

What is the composition - two parts

Answer 2

genetic material - made from either DNA or RNA
Capsid - a protein coat that surrounds and protects the genetic material

envelope of lipids - surrounds the protien coast when the are outside a cell

Question 3

What is a viral capsid

Answer 3

made of multiple units of the same protein building block know as capsomers- arranged in pattern around nucleic acid

Question 4

What are the three symmetries of the viral capsid

Answer 4

helical - TMV
Icosahedral - Adenovirus
Complex - Bacteriophage

Question 5

What is the Viral Genome

Answer 5

made up of nucleic acid RNA, DNA
linear - Pox virus
circular - hepatitis B
segmented - influenza

Question 6

What is a bacteriophage

Answer 6

viruses that infect and replicate in bacteria

Question 7

What is a lytic infection and describe the lytic cycle

Answer 7

Host cell dies

1. attachment
2. Entry of Phage DNA - and degradation of host DNA
3. Synthesis - of viral genome and proteins
4. self assembly of phage
5. release - lyse cell//explodes

Question 8

What is a lysogenic infection and describe the lysogenic cycle

Answer 8

host cell (lysogen)survives
Phage DNA integrates with bacterial chromosome
Phage is copied with bacterial chromosome
many cell divisions create many infected bacteria
daughter cell with prophage
sometimes phage exits bacterial chromosome initiating a lytic cycle

Question 9

What is induction

Answer 9

changes in growth conditions, UV irradiation