Exam6_Ch. 13

>bacteriophage

(1) Attachment Tail fibers attach to cell wall proteins (2) Entry Viral DNA injected into host cell (3) Uncoating *not required* (4) Biosynthesis In cytoplasm (5) Release Host cell lysed The above is the LIFE CYLE of: >animal virus >plant virus >bacteriophage

> host plasma membrane surrounds whole virion and forms a vesicle

In viral entry by endocytosis... > host plasma membrane surrounds whole virion and forms a vesicle > host plasma membrane surrounds only viral protein coat and forms a vesicle > host plasma membrane surrounds only viral nucleic acid and forms a vesicle

> Creutzfeldt-Jakob disease

Eating meat from cattle with bovine spongiform encephalitis can cause a variant of _______ in humans. > Fatal familial insomnia > Creutzfeldt-Jakob disease > Alzheimer's disease

> budding

Enveloped viruses are usually released from the host cell by... > budding > lysis of the host cell > endocytosis > phagocytosis

>Herpes simplex, Varicella zoster, HIV 1 and 2, HTLV 1 and 2

Latent viral infections can remain in host cells for long periods of time without causing disease because virus production stops. These types of viruses can become reactivated when host is under stress (colds, fever) or when host is immunocompromised. Which of the following are latent viral infections? >Hepatitis B, Human Papilloma Virus, Epstein-Barr Virus >Herpes simplex, Varicella zoster, HIV 1 and 2, HTLV 1 and 2

> retrovirus

MATCH A group of viruses with RNA genomes that carry the enzyme reverse transcriptase and form a DNA copy of their genome during their reproductive cycle. > herpesvirus > adenovirus > retrovirus

> protein coat that protects the nucleic acid

MATCH. __ Capsid > An additional layer external to the capsid; made up of lipids, proteins, and carbohydrates > protein coat that protects the nucleic acid

> An additional layer external to the capsid; made of lipids, proteins, and carbohydrates

MATCH. __Envelope > An additional layer external to the capsid; made of lipids, proteins, and carbohydrates > A nucleic acid core surrounded by a protein coat

> A *PROTEIN-CARBOHYDRATE* structure that projects from the surface of certain viruses (Influenza); may or may not be on an envelope.

MATCH. __Spikes > A nucleic acid core surrounded by a protein coat. > A *PROTEIN-CARBOHYDRATE* structure that projects from the surface of certain viruses (Influenza); may or may not be on an envelope.

b) the spectrum of organisms that a virus attacks.

Host range means: a) the average number of species susceptible to the virus. b) the spectrum of organisms that a virus attacks.

False [That's FALSE! A naked virus is brought into the host cell by endocytosis. It has no envelope to fuse with the cell membrane.]

True or False A naked virus fuses with host cell membrane.

True

True or False A portion of the viral envelope comes from the cell membrane of the host cell.

True

True or False Retroviruses have their own DNA polymerase (reverse transcriptase) that copies their RNA genome into DNA. Note: Examples of (RNA) Retroviruses are: *HTLV-1 (Adult T-cell leukemia) *HTLV-2 (lymphoma) *Sarcoma retroviruses cause leukemias in animals *HIV-1 and HIV-2, that cause AIDS

False [That's FALSE! Viruses with spikes usually enter host cells by FUSION. The envelope of the virus fuses with the host cell membrane.]

True or False Viruses with spikes usually enter host cells by endocytosis.

False

True or False. *An enveloped virus is damaged easily by environmental conditions.

True

True or False. Host range is determined by the presence of RECEPTORS (usually proteins) on the cell surface.

True

True or False. Major groups of viruses are distinguished by their nucleic acid content.

True

True or False. Viruses are obligatory intracellular parasites.

True

True or False. Viruses that infect bacteria are called bacteriophages.

> Cytoplasmic matrix

Viral RNA is replicated in the host cell... > Cytoplasmic matrix > Nucleus > Wall > Mitochondria

> attach specifically to host cell receptors

Viral spikes... > attach non-specifically to host cell receptors > attach specifically to host cell receptors > are present in all viruses

> Degrade host cell DNA

Virulent and nonvirulent viruses may do any of the following but NOT... > Inhibit host cell DNA synthesis > Inhibit host cell RNA synthesis > Inhibit host cell protein synthesis > Stimulate host cell macromolecule synthesis > Degrade host cell DNA

> naked

Viruses (like Adenovirus) lack an envelope and are called ________ viruses. > non- > naked > enveloped

> all of the above

What are oncogenes? > tumor suppressing genes (stop growth) > growth factor genes (regulate cell growth) -->mutation in this gene means it can't regulate--causing cell to divide & accelerating cell growth > genes that can transform normal cells into CANCER cells. > all of the above

> fold, clumps

How do prions cause tissue damage? The infectious unit is an abnormally folded prion protein, which can cause other normal prion proteins to ___ abnormally and form ____ or aggregates -->which damage brain tissue and causes neurodegenerative changes > fold, clumps > rupture, clumps

False

True or False *A single virus can contain both DNA and RNA as its genetic material.

>animal virus

(1) Attachment- attaches to the receptor Attachment sites are plasma membrane proteins and glycoproteins (2) Entry- virus enters cell Capsid enters by endocytosis OR fusion (3) Uncoating- takes off capsid, once inside it lives off nutrients in cell Enzymatic removal of capsid proteins (4) Nucleic acid biosynthesis- copies the new virus, creates protiens In nucleus (DNA viruses) OR in cytoplasm (RNA viruses) (5) Release of virions- matured viruses Enveloped viruses bud out; nonenveloped viruses rupture plasma membrane The above is the LIFE CYLE of: >animal virus >plant virus >bacteriophage

b) herpesvirus

*Epstein-Barr is what type of virus? a) reovirus (double stranded RNA) b) herpesvirus (double stranded DNA) c) retrovirus (viruses that contain a reverse transcriptase that copies their RNA genome into DNA) d) adenovirus (double stranded DNA; common cold)

c) protein coat or shell of the virus

*The viral capsid is the: a) genetic material of the virus b) virus enzymes c) protein coat or shell of the virus

c) 20%

*What percentage of human cancers are known to be caused by viruses? a) 25% b) 50% c) 20% d) 15%

Persistent --> Yes, you can

Can you detect a *persistent* virus in blood/tissue? Persistent --> Yes, you can Persistent --> No, you can't

> antigen

A substance that when introduced into the body stimulates the production of an antibody; this category include toxins, bacteria, foreign blood cells, and the cells of transplanted organs. > antigen > antibodies

Latent --> No, you can't

Can you detect a *latent* virus in blood/tissue? Latent --> Yes, you can Latent --> No, you can't

Epstein-Barr virus (EBV)>herpesvirus>DNA Oncogenic Virus> mononucleosis>Burkitt lymphoma, Hodgkin's disease>infects B lymphocytes/white blood cells>transforms them to lymphoblasts=immortal.

FYI - Epstein-Barr ANSWER: Epstein-Barr virus (EBV)>herpesvirus>DNA Oncogenic Virus> mononucleosis>Burkitt lymphoma, Hodgkin's disease>infects B lymphocytes/white blood cells>transforms them to lymphoblasts=immortal. Epstein-Barr virus (EBV) is a type of herpesvirus that is well known for causing mononucleosis. It also contributes to the pathogenesis of four human tumours: the African form of Burkitt lymphoma, B-cell lymphomas in individuals whose immune systems are impaired from human immunodeficiency virus (HIV, the causative virus of AIDS) infection or the use of immunosuppressant drugs in organ transplantation, nasopharyngeal carcinoma, and some kinds of Hodgkin disease. EBV infects B lymphocytes, one of the principal infection-fighting white blood cells of the immune system. It does not replicate within the B cells; instead, it transforms them into lymphoblasts, which have an indefinite life span. In other words, the virus renders these cells immortal. Burkitt lymphoma is endemic in certain areas of equatorial Africa and occurs sporadically in other parts of the world. As is the case with other cancer-inducing viruses, it is likely that EBV serves as only the first step toward malignant transformation and that additional mutations are required for bringing about this process.

Human papillomavirus (HPV)>DNA Oncogenic Virus>from warts to genital cancer>Diff. in binding ability correlate w/ability to activate cell growth = malignant potential

FYI - HPV ANSWER: Human papillomavirus (HPV)>DNA Oncogenic Virus>from warts to genital cancer>Diff. in binding ability correlate w/ability to activate cell growth = malignant potential More than 70 types of human papillomavirus (HPV) have been described. Some cause benign papillomas of the skin (warts). Other strains, particularly HPV-16 and HPV-18, are linked to genital and anal cancers. These viruses are sexually transmitted. HPV-16 and HPV-18 are found in the majority of squamous-cell carcinomas of the uterine cervix. Genital warts with low malignant potential are associated with HPV-6 and HPV-11. When transforming DNA viruses infect a cell, they integrate their DNA into the genome of the host. At this point the virus does not reproduce but only produces the proteins necessary to commandeer the DNA synthesis machinery of the host cell. Two of these viral genes, E6 and E7, can act as oncogenes. The proteins they encode bind to the protein products of two important tumour suppressor genes, p53 and RB, respectively, knocking these proteins out of action and allowing the cell to grow and divide. The E6 and E7 proteins of HPV-16 and HPV-18 bind to the RB and p53 proteins very tightly; in contrast, the E6 and E7 proteins of HPV-6 and HPV-11 (the low-risk types) bind RB and p53 with low affinity. The differences in binding ability of these proteins correlate with their ability to activate cell growth, and they are consistent with the differences in malignant potential of these virus strains.

HTLV-1>Human T-lymphotropic virus>Retrovirus>RNA Oncogenic Virus>Adult T-cell leukemia>Japan & Caribbean>reverse transcriptase> envelope w/spikes>infects helper T lymphocytes>(attacks same receptor as HIV)>continuous proliferation of infected T-cells>causing greater risk for secondary mutations>cancer.

FYI - HTLV-1 ANSWER: HTLV-1>Human T-lymphotropic virus>Retrovirus>RNA Oncogenic Virus>Adult T-cell leukemia>Japan & Caribbean>reverse transcriptase> envelope w/spikes>infects helper T lymphocytes>(attacks same receptor as HIV)>continuous proliferation of infected T-cells>causing greater risk for secondary mutations>cancer. Only one human retrovirus, the human T-cell leukemia virus type I (HTLV-I), is linked to a human tumour. This virus is associated with a T-cell leukemia/lymphoma that is endemic in the southern islands of Japan and the Caribbean basin but that also is occasionally found elsewhere. HTLV-I infects helper T lymphocytes (the same type of cell that is infected by HIV). Infection occurs when infected T cells are transmitted via sexual intercourse, blood transfusion, or breast feeding. Only about 1-3 percent of infected individuals will develop leukemia, and then only after a period of 20 to 30 years. HTLV-I differs from other oncogenic retroviruses in that it does not contain a viral oncogene and does not integrate into specific sites of the human genome to disrupt proto-oncogenes. Although the mechanism of transformation is not clear, a viral protein named tax, which promotes DNA transcription, may be involved in setting up an autocrine (self-stimulating) loop that causes continuous proliferation of infected T cells. When cells are constantly dividing, they are at greater risk from secondary transforming events (mutations) that will ultimately lead to the development of cancer.

Hepatitis B (HBV)>DNA Oncogenic Virus>LIVER CANCER

FYI - Hepatitis B ANSWER: Hepatitis B (HBV)>DNA Oncogenic Virus>LIVER CANCER Hepatitis B virus (HBV) is endemic in Southeast Asia and sub-Saharan Africa, areas that have the world's highest incidence of hepatocellular carcinoma (liver cancer). This and other epidemiological observations, as well as experimental evidence in animal models, have established a clear association between HBV and liver cancer. The precise role of hepatitis B virus in causing liver cancer is not yet understood, but evidence suggests that viral proteins disrupt signal transduction and thereby deregulate cell growth.

>Adult T-cell leukemia

HTLV-1 is a retrovirus that causes: >Lymphoma >Adult T-cell leukemia > leukemias in animals >AIDS

>Lymphoma

HTLV-2 is a retrovirus that causes: >Lymphoma >Adult T-cell leukemia > leukemias in animals >AIDS

> end

Hemagglutinin (HA) of the Influenza virus functions at the beginning of infection whereas, Neuraminidase (NA), functions at the ____. > middle > end

b) envelope

Naked or non-envelope viruses lack ________? a) spikes b) envelope c) capsid

>All DNA oncogenic viruses and the retroviruses (of the RNA oncogenic viruses)

Oncogenic group of viruses are capable of producing TUMORS. Which category below is known to cause cancer: > All DNA oncogenic viruses; ex. Epstein-Barr virus (herpesvirus); Hepatitis B (HBV), human papillomaviruses (HPV) > Only retroviruses of the RNA oncogenic viruses; ex. HTLV-1 & HTLV-2, sarcoma > All RNA oncogenic viruses and all DNA oncogenic viruses >All DNA oncogenic viruses and the retroviruses (of the RNA oncogenic viruses)

>Hepatitis B, Human Papilloma Virus, Epstein-Barr Virus

Persistent viral infections are virus that continues to replicate in the host despite host defense mechanisms aimed at killing it. Virus can be detected in the host at all times, UNLIKE w/latent infections. Which of the following are persistent viral infections? >Hepatitis B, Human Papilloma Virus, Epstein-Barr Virus >Herpes simplex, Varicella zoster, HIV 1 and 2, HTLV 1 and 2

> all of the above

Pions are...? >An infectious agent consisting of a self replicating protein with no detectable nucleic acid > involves degeneration of BRAIN TISSUE > proteinaceous infectious particle > "mad cow" disease, scrapie in sheep > all of the above

c) both a & c

Some envelopes are covered by protein/carbohydrate structures called spikes; influenza virus has what kind of spikes in its envelope? a) hemagglutinin b) neuraminidase c) both a & c

b) lipids, proteins, carbohydrates

Some viruses have an envelope which is an additional layer external to the capsid; usually consists of some combination of: a) nucleic acid, carbohydrates, lipids b) lipids, proteins, carbohydrates c) proteins, carbohydrates, spikes

> Hemagluttinin

The _____ of the influenza-enveloped virus appear to be involved in attachment to the host cell receptor site. > Pili > Fimbriae > Flagellae > Hemagluttinin > Neuraminidase

> All of the above

What are the characteristics used to classify viruses? > phenotypic (observable) characteristics > [Familia] based on morphology, type of nucleic acid, strategy for replication... > [Species] based on the same genetic info and ecological niche a group of viruses share > Viral species are named currently w/the common English name > All of the above ************************************************************* Notes: *phenotypic characteristics: such as morphology, nucleic acid type, strategy/mode of replication, host organisms, and the type of disease they cause *Virus family names suffix = -viridae, genus = -virus.

> throughout the body

Where might we find normal prions? > cows only > throughout the body *NOTES: Normal prion proteins exist in many places throughout the human body. Specifically, they are expressed in a variety of cells within the nervous system (i.e. brain, spinal cord), some immune cells, bone marrow, spleen, lymph nodes, blood, peripheral tissues (i.e. retina in the eye) and organs. However, the disease state arises from damage to neural and glial cells. It is only when these normal prion protein changes into a different folded conformation that causes the infectious form of prion proteins responsible for prion diseases. Prion proteins in humans: ORGAN/TISSUE: *BRAIN *CEREBELLUM *HIPPOCAMPUS *STOMACH, KIDNEY, SPLEEN *MUSCLE *BLOOD

> Hemagglutinin (HA)

Which ANTIGENIC component of the Influenza virus is notorious for it's ability to CLUMP RED BLOOD CELLS and is the *receptor binding protein* that allows for the virus to BIND/ATTACH to the host's cell membrane, fuse, and once inside, releases it's viral contents in cytoplasm? > Hemagglutinin (HA) spikes > Neuraminidase (NA) spikes

> Neuraminidase (NA) spikes

Which ANTIGENIC component of the Influenza virus is notorious in aiding CELL PENETRATION by CLEAVING neuraminic acid (sialic acid) to RELEASE PROGENY VIRUS from the infected cell? > Hemagglutinin (HA) spikes > Neuraminidase (NA) spikes

> Human papilloma virus

Which of the following has been linked to cervical cancer? > Epstein-Barr virus > Human T-cell lymphotropic virus > Human immunodefficiency virus > Human papilloma virus > Human herpes virus 8

> Hemagglutinin & Neuraminidase spikes. [That's CORRECT! Viruses may or may not have spikes BUT remember, they are external features (spikes) and NOT part of the GENETIC MATERIAL]

Which of the following is NOT a descriptive feature of the genetic material of viruses? > contain either DNA or RNA; single or double-stranded > the genome is typically organized as a long molecule that is usually straight/linear, or circular, or divided into separate molecules > nuclei acid to protein ratio = 1% : 50% > Hemagglutinin & Neuraminidase spikes

> Hepatitis B virus

Which of the following is the virus *always detectable* after infections? > Hepatitis B virus > Herpes simplex virus > Varicella-zoster virus > Epstein-Barr virus

a) HIV

Which one is an enveloped virus (has an additional layer external to the protein coat capsid) a) HIV (RNA virus; Human immunodeficiency virus; member of the retrovirus/retroviridae family) b) Adenovirus (double stranded DNA virus; over 50 strains; common cold)

b) Adenovirus

Which one is considered a naked or non-enveloped virus? a) HIV (RNA virus; Human immunodeficiency virus; member of the retrovirus family) b) Adenovirus (double stranded DNA virus; over 50 strains; common cold)

> provirus

___ is viral DNA that is integrated into the host cell's DNA. It's role in latent infections is to integrate their DNA into the host cells DNA where they stay and cannot be detected by immune system or anti-viral drugs. (Ex. herpes, HIV) > prion > provirus