Exam 1 Chapter 21 Viruses

Question 1

capsid

Answer 1

outer layer of virus composed of proteins subunits.

Protein on surface can interact with a protein on surface of host cell.

Question 2

Nucleic Acid Core

Answer 2

Inner most portion is made of DNA or RNA

Question 3

envelope

Answer 3

possessed by some viruses.

are a lipid membrane that is rich in lipoprotein and glycoproteins surrounding virus capsid.

Question 4

spike

Answer 4

glycoproteins that project from some enveloped viruses allowing for attachment of the virus to the targeted host cell.

Question 5

Virus

Answer 5

intracellular parasites. Do not possess cell.

Are essentially chemical complexes of RNA or DNA protected by protein.

Question 6

Virus shapes

Answer 6

Helical: usually plant viruses
Icosahedral: usually animal viruses
Complex binary: bacteria viruses

Question 7

Viral reproduction

Answer 7

1) attachment
2) penetration
3) biosynthesis (assembly)
4) maturation
5) release

1) entry into host because portions of capsid adhere to specific receptor on host cell’s outer surface.
2) Viral nucleic acid enter host cell and codes for protein units inside capsid
3) virus takes over metabolic machinery of host cell

Question 8

host range

Answer 8

usually limited host range

Question 9

tissue tropism

Answer 9

targeting of specific range of cells within suitable organism

Question 10

transformation

Answer 10

genetic alteration of a cell’s genome by the introduction of foreign DNA

Question 11

latent virus

Answer 11

virus that is able to hide from host’s immune system by integrating itself into host cell’s genome and not producing new viruses (ex: chicken pox and HIV)

Question 12

retrovirus

Answer 12

have the enzyme reverse transcriptase.

high error rate of reverse transcriptase leads to high genetic diversity of HIV: this in turns creates difficulty in creation of vaccine.

direction of genetic information transfer in a retrovirus is RNA to DNA to mRNA to protein. (ex: HIV)

Question 13

bacteriophage

Answer 13

virus that infects bacteria

Question 14

virulent virus

Answer 14

causes lysis of their hosts.

Question 15

emergent virus

Answer 15

virus in a new host with a potential lethality rate of 50% (EBOLA) can jump from one species to another.

Question 16

viroids

Answer 16

tiny, naked molecules of RNA a few hundred nucleotides long whose sequence resembles intron sequences in rRNA genes. They cause plant diseases.

Question 17

lysogenic cycle

Answer 17

integration and stabilizing of viral genes into the host cell’s genome

Question 18

lytic cycle

Answer 18

host cell lyses, releasing many viral particles

Question 19

induction

Answer 19

switch from lysogenic prophage to a lytic cycle

Question 20

cancer

Answer 20

may be cause by viruses through triggering the expression of cancer-causing genes present in the genome.

Question 21

prophage

Answer 21

parasitic viral DNA that has been integrated in chromosomes of bacterial host.

Question 22

influenza virus

Answer 22

3 major types of flu virus (A B C).
only A can occur in human, other mammals and birds.
flu subtype is determined by the kinds of proteins representing the H and N protein spikes making up the capsid of the virus.
different strains of the virus requires different vaccines
genetic high mutation rates is primarily responsible for the high diversity in strains
genetic recombination between flu strains from different species is common

Question 23

prion

Answer 23

misshapen protein agents with no associated nucleic acid that may convert other proteins in the cell to also become these agents causes Mad cow disease and others.