MIC 206: Exam 3 chp 13

Neoplasia

Uncontrolled cell division in a multicellular animal; a mass of neoplastic cells is a tumor.

Tumor

A mass of neoplastic cells.

Benign

A non-harmful, localized tumor that stays in one place, though it can cause pain and steal space/nutrients.

Malignant

Malignant tumors also called cancers. When the cell undergoes uncontrolled division

Cancer

Malignant tumors also called cancers. (Uncontrolled activation of oncogenes can lead to cancer).

Metastasis

Metastasis occurs when tumors spread.

Lytic replication cycle as it typically occurs in bacteriophages.

1.  Lytic replication: Tail fibers attach to specific receptor proteins on the bacterial surface.

2.  Entry:Tail sheath contracts; a tube passes through the cell wall and cytoplasmic membrane, and the phage DNA is injected into the bacterium.

3.  Synthesis:Phage DNA takes over host machinery; phage proteins form and phage DNA is replicated.

4.  Assembly: 

   1. Base

   2. Tail

   3. Sheath

   4. DNA

   5. Capsid

   6. Mature head

   7. Tail fibers

   8. Maure virion

5.  Release:The bacterium fills with virions and bursts (lysis); new bacteriophages exit through the cell wall and can infect other bacteria.

Assembly in lytic cycle

Assembly: 

1. Base

2. Tail

3. Sheath

4. DNA

5. Capsid

6. Mature head

7. Tail fibers

8. Maure virion

List the characteristics by which viruses are classified.

1. Nucleic acid Structure: DNA OR RNA(Never both)

2. Kinds of cells (organism) they infect (host range)

3. Size and shape of the virus

-Helical- hallow tube shape

- Polyhedral- spherical shape

- Complex- irregular shape

4. Structure of protein coat (capsid):Capsids (capsomeres) may be made of single or multiple types of proteins

5. Presence or absence of an envelope

Name the 3 sizes and shapes of the virus?

- Helical- hallow tube shape

- Polyhedral- spherical shape

- Complex- irregular shape

Discuss the origin, structure, and function of the viral envelope.

Viral envelopes are derived from host cell membranes and contain viral-encoded proteins, including glycoprotein spikes.

How do viruses of fungi, plants, animals, and bacteria differ from each other?

All types of organisms are susceptible to some virus(differ in host specificity, each virus is specific for them).

Explain the mechanism by which viruses are specific for their host cells.

A virus can attach and infect only cells that display the matching receptor. Attachment molecules-proteins or glycoproteins spikes on the capsid or envelope, on the host cell are complementary proteins or glycoproteins in the plasma membrane. 
Ex: HIV->Humans; Parvo-> Dog’s Expectations: Influenza, Covid-19

What type of viral genomes does cells have?

ALL Cells have dsDNA

What type of viral genomes does a virus have?

Virsus can have RNA OR DNA (BUT NEVER BOTH!!!)

Whar are the additional features that Virions will possess?

– Enzymes need to complete their life cycle 

– Glycoprotein appendages for attachment 

– Envelope that is composed of a phospholipid bilayer.

Def of Viruses

are ultramicroscopy measured in nanometers 10nm-500nm, have no organelles and no dependent metabolism and do not divide or grow which make them acellular (obligated intercellular parasites). They must infect a host cell inorder to replicate and divide  by forming an assembly-line using enzymes and organelles of the host cell.  When outside(extracellular state) cellular hosts they are called  virions which consist of a capsid protein coat that protects the nucleic acid (viral genome) which is either DNA or RNA (not both only one). 

What is the name of protein coat that protects the nucleic acid (viral genome) which is either DNA or RNA (not both only one)?

capsid

A virus when outside(extracellular state) cellular hosts they are called?

virions

What percentage of human cancers are caused by DNA and RNA viruses?

25%

Role of viruses in causing cancer? Mechanism 1

1. Virus inserts its viral genome into the middle tumor repressor gene→gene stops functioning, & the cell loses control of the cell cycle

Cellular basis of cancer

Cell division of animal gene is under strict genetic control

Genes dictate that some cells can no longer be divided at all

Cells that can divide or prevented from unlimited division

Problems arise when genes for cell division and growth are "turned on" (Proto-oncogenes) or when genes inhibiting division are "turned off" (tumor suppressors).

Uncontrolled activation of oncogenes can lead to cancer.

HPV16 E6 and E7 protien

Example of oncogenes:HPV16 carries and over-expresses the viral proteins (E6 and E7) that promote uncontrolled cell division and lead to cancer.

Role of viruses in causing cancer? Mechanism 2

2. Some viruses increase the rate of (transcription/translation) TXC/TXL of oncogenes within the host cell→ increasing cell division rate.

Role of viruses in causing cancer? Mechanism 3

3.Some viruses carry their copies of cell division genes (oncogenes) as part of their genomes→increasing the cell division rate.

Epstein Barr virus causes?

This is the virus that causes Mono

Human T-lymphotropic virus-1 (HTLV-1) is a?

This is a retrovirus!

Viroids

Are extremely small, circular pieces of single-stranded RNA (ssRNA) that are infectious and pathogenic in plants (e.g., Potato Viroid). They are similar to RNA viruses but lack a capsid.

Protein Coding Viroid

Viroid RNA does not code for proteins.(lack a capsid)

Mechanism of Action & Disease for Viroid

• Viroid RNA adheres to complementary plant RNA.

• Plant enzyme degrades the dsRNA.

• Results in a disease state.

An example of Viroid?

Potato Viroid

HIV Target Cells?

CD4 T-cells and Macrophages.

HIV 3 unique enzymes

• Reverse transcriptase (retrovirus)

• Intergrase (Integrate viral DNA into host genome)

• Protease

Influenza unique enzymes?

RNA-dependent RNA polymerase

Influenza Glycoproteins in the Envelope?

– Hemagglutinin (H): Binds to the receptor (sialic acid) on the host cell
– Neuraminidase (N): Viral exit, cleaves H protein from sialic acid

Drift

minor change

shift

major one

Burst time

period of time required to complete the entire lytic process, from attachment to release

Burst size

total number of new virions released from a given population of lysed bacterial cells

HIV; Carry 3 unique enzymes

• Reverse transcriptase (retrovirus) – RNA→DNA (RNA-dependent DNA polymerase) » Error-prone

• Intergrase (Integrate viral DNA into host genome)

• Protease (Cuts up the viral Proteins)

– Infects CD4 T-cells and Macrophages

influenza; Carry unique enzymes – RNA-dependent RNA polymerase