VIRUSES Viruses do not exhibit ALL of the characteristics of life. They… 1. are not living 2. are not cells 3. do not have cell parts. 4. cannot carry on metabolic functions

A nonometer is 1 billionth of a meter.

Viruses capsids are made up of subunits (monomers) called capsomeres. Bacterial viruses are called phages. There are chemical markers on the surface of viruses that allow them to invade a host’s cell and attach to the surface of that cell. It is like their fake ID badge that fools the host cell into thinking it is safe to attach.

Most DNA viruses are relatively stable and do not normally mutate. RNA viruses are subjected to constant mutations, and this is one of the main reasons why vaccines for Retroviruses are very difficult to develop. If the surface markers on a viral capsid change, the vaccination may not work as well or at all after the mutation.

Tobacco Mosaic Virus has a helical capsid enclosing RNA.

Adenoviruses have a polyhedral capsid with glycoprotein spikes with a DNA core.

Flu viruses have 8 capsids with an RNA genome wrapped in a membranous envelope embedded with glycoproteins.

Phage T4 has a polyhedral head and a tail apparatus Phage T4 has a polyhedral head and a tail apparatus. It is also called a bacteriophage.

Virus Nucleic Acid 1. may be a single strand consisting of as few as 5 genes 2. may be multimolecular with several hundred genes 3. may be double stranded. 4. may be DNA or RNA

Prions are: - infectious agents composed misfolded protein. - They contain no nucleic acid. - This protein polymerizes into rods with the characteristics of amyloid. Amyloid is a generic term referring to any vissually homogenous, waxy, clear glycoprotein; it is related to many human diseases such as:

Alzheimer's disease Signs of Alzheimer’s Memory loss Difficulty solving problems. Difficulty with familiar tasks. Confusion of time or place. Trouble understanding visual images. New trouble speaking or writing. Misplacing things more often. Increased poor judgement. Withdrawl form social activity. Changes in mood and personality.

CJD is a human form of mad cow disease Creutzfeldt-Jakob disease CJD is a human form of mad cow disease

Down's Syndrome also called Trisomomy 21

Fatal Familial Insomnia Fatal Familial Insomnia (FFI) is a very rare inherited, dominant prion disease of the brain. The offspring have a 50% chance of inheriting it and developing the disease. The disease's is untreatable and ultimately fatal. They just can’t fall asleep!

Student Worksheet: Virus Structure Worksheet