Lec. Dr. Ahmed Yaseen Abed

Introduction

 Cell Growth Regulation Cell growth is the cell proliferation (the increase in cell numbers that occurs through repeated cell division). Cell growth is regulated by two groups of regulatory genes: 

A. Proto-oncogenes (cellular oncogene, c-onc) Are normal genes which control cell proliferation Have the potential to contribute to cancer development if their expression is altered (changed into oncogenes) Oncogenes are genes that cause cancer

Introduction

 Bacteriophages are viruses that infect bacteria. Replicating within the bacterial cell, therefore they are obligate parasites. Infection with bacteriophages is restricted to particular strains within a single bacterial species. Phages exist in many forms and infect all living systems such as animals, plants, insects and bacteria, therefore phages are ubiquitous in nature and they have been shown to be found in soil and sediment. 

Ecological Impact 

Introduction

 Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the common cold (which is also caused by other viruses, predominantly rhinoviruses). More lethal varieties of the virus can cause SARS, MERS and COVID-19, which is causing the ongoing pandemic. In cows and pigs, they cause diarrhea, while in mice they cause hepatitis and encephalomyelitis

Enteric viruses (Polio Virus, Rota virus and Rio) Characteristic properties: - Small, non-enveloped viruses -Multiply in the gut mucosa -Transmitted from person to person by the fecal-oral route (ingestion disease), - Spread throughout the body via the blood stream -Most infections occur during childhood, and they are usually transient but produce lifelong immunity, -Clinical syndromes are generally mild -Infections may cause serious disease e.g. paralytic poliomyelitis, meningitis, or myocarditis. - There is a high degree of serological cross reactivity between the 72 members.

The term myxovirus was coined for a group of enveloped RNA viruses that have the ability to adsorb onto mucoprotein receptors on erythrocytes, causing hemagglutination. It included influenza, mumps, parainfluenza, and Newcastle disease viruses

Human immunodeficiency virus (HIV) Is a retrovirus that causes human AIDS. Many retroviruses infect vertebrates, One genus of retrovirus, Lentivirus, includes the subspecies HIV-1 and HIV-2, which cause AIDS. Family: Retroviridae Genus: Lentivirus Species: Human Immunodeficiency Virus (HIV)

●HIV infects mainly CD4+ T cells, macrophages, and dendritic cells which express the surface receptor CD4. ●Destroying CD4+ T cells leads to opportunistic infection. 

Hepatitis is a clinical syndrome caused by many pathogens including viruses. There are six medically important viruses that are called hepatitis viruses because their main site of infection is liver. These viruses are hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), hepatitis E virus (HEV), and newly described G virus (HGV). Although these viruses infect the liver as common target organ, they however, differ greatly in their morphology, replication pattern, and course of infection. Hepatocytes are the primary target of true.

Nearly everyone will be affected by some type of herpes virus at some time in his or her life. Herpes simplex virus belongs to the family of herpesviridae which consists of more than 80. distinct types of viruses that are found in nearly every kind of animals such as fishes, frogs, birds ,cats, dogs, mice, snakes, lizards, monkeys, cows, horses, humans, and more Classification The classification of herpes viruses is complex!

Each virus carries within the protective capsid a nucleic acid-based blueprint for replication of infectious virus particles (virion). Once a virus has invaded a cell, it is able to direct the host cell machinery to synthesize new progeny. The viral genome may be composed of RNA or DNA, single or double stranded. Encoded proteins may be nonstructural, such as nucleic acid polymerases required for replication of genetic material or structural, those proteins necessary for assembly of new infectious virions.

Classification of viruses is based on the following characteristics:- 1- Virion morphology, including size, shape, type of symmetry, presence or absence of enveloped. 2. Virus genome properties, including type of nucleic acid (DNA or RNA), size of genome, strandedness (single or double), whether linear or circular, positive or negative sense (polarity), segments (number, size). 3.Physicochemical properties of the virion, including PH stability, thermal stability, and susceptibility to physical and chemical agents especially ether and detergents. 4.