Test Nine Lecture Four

73. Which statement does not describe the structure of a virus?

• The center of the virus (the core) has RNA or DNA that is a nucleic acid, which has to be surrounded by a protein coat called a capsid

• They cannot replicate on their own

• Can only reproduce when they enter the cell and hijack the cell’s machinery

• Animal viruses have an envelope containing lipids surrounding them with molecules for extra protection

74. Why are viruses not considered living organisms? (know the information we discussed on viral replication)

Viruses cannot replicate on their own. Instead, they must utilize the cellular machinery of their host cells upon entering. They hijack your ribosomes and make any proteins or enzymes necessary.

75. Most viruses have an overall structure that is either _____ (rod-like or threadlike) or _____ (a roughly spherical shape). Fill in the blanks.

helical

isometric

76. The suitable cells for a particular virus are collectively referred to as its _______. Fill in the blank.

host range

77. According to the video on Viruses, what type of chemical trigger is there that can cause a virus’s lysogenic cycle to go into the lytic cycle?

Lack of food or chemical trigger.

78. According to the video on Viruses, why is HIV so dangerous to our cells?

It binds to helper T cells, but those cells protect the immune system. This means no more immune system cells so the person infected with hiv is vulernable to other diseases.

79. According to the video on Viruses, can viruses be used for good or are they all bad?

Viruses can be used for good in gene therapy. Viruses can also target certain pests.

80. What is a bacteriophage?

Viruses that infect bacteria

81. What is the difference between a T-3/7 or a T-even bacteriophage?

T-3 & T-7

• Icosahedral head

• Short tails, which determine the length of the legs

T- even

• T-2, T-4, & T-6

• Icosahedral head, but the capsid is specific

• Long neck, with a collar and long whiskers 

• More complex base plate

82. According to the video The Deadliest Being on the Planet Earth – The Bacteriophage, what percent of ocean bacteria are killed by phages every day?

40%

83. According to the video The Deadliest Being on the Planet Earth – The Bacteriophage, do bacteriophages have specific hosts?

Yes, they each specialize in hunting specific types of bacteria.

84. According to the video The Deadliest Being on the Planet Earth – The Bacteriophage, by what year is it estimated superbugs will kill more people than cancer? How many people are killed by antibiotic resistant bacteria every year approximately?

By 2050. More than 23k people die from antibiotic resistant bacteria each year.

85. According to the video The Deadliest Being on the Planet Earth – The Bacteriophage, why are we now injecting ourselves with certain viruses? Can bacteriophages hurt your cells?

We are exploring the uses of bacterophages to vure viruses which is why we inject ourselves with them. Bacteriophages can’t hurt human cells.

86. According to the video The Deadliest Being on the Planet Earth – The Bacteriophage, how was a bacteriophage recently used to cure a disease?

Thousands were injected into a patient with a lung virus along with antibacterials. The phages were able to kill the virus.

87. Which of these is not a step in the lytic cycle (go by the diagram on the PPT)?

1. Attachment: virus attaching to the cell wall

2. Penetration: viral DNA injected into the cell

3. Synthesis: protein and nucleic acid

4. Assembly: involves spontaneous assembly of capsid and enzyme to insert DNA\

5. Release: lysis of cell

88. Which of these is not a step in the lysogenic cycle (go by the diagram on the PPT)?

1. Integration: of genome leads to prophage

2. Propagation: of prophage along with host genome

   1. Reproduction of lysogenic bacteria

3. Cell Stress

4. Induction: prophage exits the bacterial chromosome, viral genes are expressed

5. Synthesis: protein and nucleic acid

6. Assembly: involves spontaneous assembly of capsid and enzyme to insert DNA\

7. Release: lysis of cell

89. What is the difference between a virulent and temperate virus?

Virulent

• Shows symptoms

• Destroys the cell

Temperate Virus

• shows no symptoms

• Does not utilize the energy within your cell

• connects to your DNA

• replicates every time you replicate

90. What is a prophage?

Connects to your DNA and nucleus, but it stays there until something triggers it to go into the lytic cycle.

91. HIV is a retrovirus. What is a retrovirus?

RNA viruses that transcribe their genes using our cell machinery to turn into DNA and hook onto your DNA. It changes an RNA virus to a DNA virus.

92. How does the HIV virus compromise your immune system?

1. White blood cells are CD4s+ they get destroyed when you have a lysogenic cycle switching to lytic, and the body cannot destroy any invaders or viruses at this time. You have no more immune systems.

2. Latency period from HIV to AIDS is usually 8-10 years on average and can transmit it during this period. 

3. No symptoms can be seen, but it is highly contagious

4. Random mutational event the virus quickly overcomes the immune system and you have aids.

93. How does the HIV virus enter a human macrophage?

It will enter a macrophage after certain receptors are used and the HIV virus will go in it through endocytosis.

94. Once the HIV virus enters your macrophage, it begins using reverse transcriptase. What is reverse transcriptase and what does it do to the HIV virus?

Reverse transcriptase is an enzyme, which synthesizes a double strand of DNA complementary to the virus’ RNA.

95. How does the HIV virus (after replication) leave your human cells?

It does not kill the cell in the beginning stages,  a new virus is released into the cell, and the virus will leave the cell and move onto other macrophages through a process called budding.

96. When a mutation occurs in a certain gene by HIV, the body’s T cells (lymphocytes) become infected with HIV and rupture the cells which lead to the disease called ___________. Fill in the blank.

early onset AIDS