LEQ: How does microbial DNA impact our lives?

10.17 to 10.23

Viral life cycles

VIRAL LIFE CYCLE

Lytic – viral replication cycle resulting in the release of new viruses by breaking open the host cell. Viral DNA directs host cell to make new viruses.

Lysogenic – viral replication cycle in which the viral genome is incorporated into the host chromosome as a prophage – new phages are not produced and host is not destroyed

RNA VIRUS REPRODUCTIVE CYCLE

1. Envelope of virus fuses with cell membrane2. Enzymes remove protein coat3. Viral enzyme uses the viral RNA genome as a template for making complementary RNA which can do 2 things4. produce viral protein5. produce more viral RNA6. New protein coats surround new RNA7. Virus leaves the cell by coating themselves with cell membrane

Herpes virus Enveloped DNA

virus that reproduces in the host cell nucleus

Can remain dormant in certain nerve cells for long periods of time

Stress activates herpes virus flare ups

Polio Virus

This virus attacks nerve cells which do not divide damage is permanent

Treated with vaccine

Plant Viruses Stunt plant growth & diminish

crop yields Common plant virus – tobacco

mosaic Viruses enter through damaged

tissue Viruses transmitted to plants

via…› insects, gardeners and farmers

using contaminated tools, infected plant to offspring

How would a virus spread through an individual plant?› plasmodesmatta

EMERGING VIRUSES

AIDS – Acquired Immune Deficiency Syndrome

Caused by HIV – a RETROVIRUS (uses reverse transcriptase)

early 80’s 1st cases in US in San Francisco

Infects and kills several kinds of white blood cells

Retrovirus RNA virus that reproduces

by means of a DNA molecule; it reverse transcribes its RNA into DNA; its DNA is inserted into the chromosome; its DNA then transcribes the production of more viral RNA and viral protein

AIDS is a retrovirus because it has…› 2 copies of RNA› Reverse Transcriptase

Acquired Immune Deficiency Syndrome

and Human Immunodeficiency Virus

- are named for what they do - wipe out the

immune system.

RNA Retro Virus1. Viral envelope fuses

with cell membrane2. Enzymes remove

protein coat3. Reverse transcriptase

converts viral RNA into DNA

4. DNA is integrated into host DNA5. Viral genes are transcribed to produce more viral RNA and protein6. New viruses are assembled7. New viruses exit the cell taking host cell membrane with them *Retroviruses can be dormant for years before being expressed

EMERGING VIRUSES

Ebola

Recognized in 1976 in Central Africa

Causes hemorrhagic fever, vomiting, massive bleeding and circulatory failure – often fatal

EMERGING VIRUSES

West Nile

First seen 1990 in North America

Causes encephalitis (swelling of the brain)

Spread by mosquitoes

EMERGING VIRUSES

SARS – Severe Acute Respiratory Syndrome

February 2002 in China

Within 3 months 8,450 were infected – 10% died

Caused by corona virus

EMERGING VIRUSES

H1N1 / Swine Flu

2009 outbreak in Veracruz, Mexico

Typical flu symptoms

Virus killed more than 18,000

Emerging Viruses Mutations of existing viruses can produce

new viral diseases; diseases evolve into a new species that can infect individuals who were immune to the original strain

People come in contact with other species in the process we are exposed to the viruses that infect the other species

Spread of viral diseases is rapid due to globalization (worldwide travel), promiscuity, blood transfusions, intravenous drugs, etc…

Bacterial DN

A Transfer (1 of 3)

Transformation – the incorporation of new genes into a cell from DNA that cell takes up from the surrounding environment (Griffith)

Bacterial DN

A Transfer (2 of 3)

Transduction – the transfer of bacterial genes from one bacterial cell to another by a phage

Bacterial DN

A Transfer (3 of 3)

Conjugation – the union (“mating”) of 2 bacterial cells resulting in the transfer of DNA between the 2 cells

BACTERIAL DNA TRANSFERS New DNA integration occurs by crossing over between the 2 DNA molecules – incorporating new DNA into existing DNA

Bacterial Plasmids

Plasmid – small circular DNA found in bacteria (and yeast) that is separate fro the chromosome

F Factor – a piece of DNA that can exist as a plasmid; it carries the genes needed to make sex pili & other structures needed for conjugation; F = Fertility; allow for the spread of DNA to other cells

Bacterial Plasmids

R Plasmid – bacterial plasmid that carries genes for enzymes that destroy particular antibiotics – result in antibiotic resistant bacteria.