Week 4 Viruses Y

Question 1

Viruses definition

Answer 1

Viruses are simple, acellular entities of one or
more molecules of DNA or RNA enclosed in a
coat of protein (lipids or carbohydrates). They can
only reproduce within living cells.

Question 2

Name the different viral shapes

Answer 2

icosahedral - 20 triangular faces
helical-flexible cylinders
Enveloped
Complex - icosahedral head and helical tail

Question 3

Viruses have

Answer 3

Have simple acellular organization
Have either DNA or RNA not both
Inability to reproduce independently

Question 4

How to isolate viruses

Answer 4

Centrifugation
Precipitation
Denaturation
Enzymatic denaturation

Question 5

Acute infections

Answer 5

Short duration
■ Host normally develops long-lasting immunity

Question 6

How an animal virus replicates

Answer 6

Glycoprotein spikes of the virus bind to cell receptor, it is then engulfed (endocytosis),

Nucleic acid released from capid this is its dna

dna enters nucleus and inserts itself into the genome

replicates and releases new virus to repeat

Question 7

Bacteriophage

Answer 7

Viruses that infect bacteria

Question 8

Describe the appearance of bacteriophage

Answer 8

Capsid head containing DNA, Healical sheath as a neck, Hexagonal base plate, tail fibres as legs

Question 9

Types of bacteriophage

Answer 9

virulent
temperate

Question 10

Lytic cycle

Answer 10

ruptures cell

Question 11

Lysogenic cycle

Answer 11

Instead of
destroying host to produce virus progeny,
the viral genome remains within the host
cell and replicates with the bacterial
chromosome.

Question 12

Holin

Answer 12

enzyme which destabilizes the host cell membrane
(pokes holes)

Question 13

Lysin / lysozymes

Answer 13

phage enzyme which breaks host cell
wall (lyses host bacteria)

Question 14

Lysogeny

Answer 14

WHEN A VIRUS INTEGRATE WITH THE CELL’S
GENOME.

Question 15

Viroids

Answer 15

Smallest known infectious pathogens, made up of a short strand of circular rna, mostly causes plant diseases

Question 16

Prions

Answer 16

Misfolded proteins that can transmit their shape to other regular proteins, causes transmissible neorodegenerative diseases

Question 17

In which of the following stages of the viral cycle do enveloped viruses usually acquire their envelope
Penetration.
Component biosynthesis.
Assembly.
Release.

Answer 17

Release

Question 18

When the viral genome is integrated into the host chromosome but does not result in the lysis of the host cell, it is referred to as

Answer 18

Prophage

Question 19

In a one-step growth experiment, the time during which there is a rapid lysis of host cells and release of infective virons is called

Answer 19

Burst phase

Question 20

An Anticodon consists of three nitrogen bases found on

Answer 20

The Trna

Question 21

What do you understand by bacteria that are naturally «competent»

Answer 21

Taking up free dna

Question 22

The majority of fungi are photosynthetic

Answer 22

False