2.10 Mutuations,Viruses, Disease

Sickle Cell Mutuation?

Change in a single amino acid in one of the polypeptides in hemoglobin protein

—single nucleotide modification (Point mutation)

A—>T:6th codon

-Amino acid changes from Glutamic acid to Valine at position 6

—Hbs instead of normal Hba

Mutation

Change to genetic info of cell or virus

-Involves larger regions of a chromosome or just a single nucleotide pair

Base substitutions

One nucleotide is replaced by another in DNA. Can change the amino acid and protein.

Nucleotide deletion

One or more nucleotides are removed from DNA

Nucleotide insertion

One ore more nucleotides are added into DNA can cause a frameshift.

Frameshift mutation

A change in reading frame of DNA,affecting all downstream amino acids. Usually caused by insertion or deletion. Protein is nonfunctional as there is a change to amino acid sequence.

Missense mutation

Single nucleotide change in DNA, changes one amino acid protein

Nonsense mutation

Single nucleotide change that creates a STOP codon in the middle of the coding sequence—→ protein is cut short

Silent mutation

A single nucleotide base is substituted in DNA, but amino acid does not change,so the protein stays the same.

Mutagens

Any physical,chemical,or biological agent that causes a mutation.

-UV:Causes thymine dimers;Replication error

-X rays or gammas: DNA strand breaks or chromosomal rearrangements

Chemical Mutagens:Chemicals that interact with DNA

What do Mutagens act as?

Carcinogen agents that cause cancer can avoid it

What do Viruses share with living organisms?

Genetic material (DNA or RNA) packaged in a highly organized structure like living organisms

Why are Viruses not considered alive?

Viruses are not cellular and cannot reproduce on their own, they need a host to replicate.

What is a virus?

An infectious particle made of genetic material (DNA or RNA) and a protein coat (capsid)

What is a capsid?

The protein coat that encloses and protects the viral genetic material

What is an envelope in a virus?

An optional lipid membrane derived from the host cell that can help the virus ENTER host cell.

What are protein spikes in a virus?

Proteins located on the capsid or envelope that help the virus ATTACH to and enter host cells.

Adenovirus?

A type of virus with double stranded DNA that can cause respiratory infections,colds,and illnesses in humans. It has a protein capsid with spikes but NO LIPID ENVELOPE.

Bacteriophage?

A virus that attacks bacteria by attaching to the surface and injecting its DNA or RNA

Lytic Cycle?

A reproductive cycle where the phage immediately takes over the bacterium (kills it by bursting) uses it to make new viruses, and then lyses (destroys) the bacterial cell to release them.

• Rapid spread of virus

• Produces many new viral particles quickly,ready to infect others

Lysogenic Cycle?

The virus hides in the bacterial DNA, prophage and can stay dominant for many generations before entering the lytic cycle.

• Virus remains hidden in prophage and is replicated along DNA host

• Virus can persist in bacterial population without killing cell, and can layer switch to the lyric cycle for rapid spread

• Long term survival,virus hides

Plant Virus?

• RNA Rather than DNA as genetic material.

To infect a plant a virus must get first past the plants epidermis, plants damaged by wind,chilling,injury or insects is more susceptible to infection.

What is the common cause of disease?

Viruses that affect animal cells

Influenza,cold viruses,measles,mumps,AIDS,polio,hepatitis,chickenpox,and herpes

What is the envelope of some animal viruses?

An outer phospholipid membrane with protein spikes that helps the virus enter and leave host cells.

Which animal viruses have RNA as their genetic material?

Flu,cold,measles,mumps,AIDS,polio.

Which animal viruses have DNA as their genetic material?

Hepatitis,chickenpox,and herpes infections.

What factors affect how harmful a virus is?

1)How fast your immune system responds

2) Whether the infected tissue can repair itself

Why is polio harmful?

Some tissues cannot repair themselves,so infection can cause permanent damage

What type of Virus is HIV?

At retrovirus that is RNA, WITH an envelope,enters cells like other enveloped viruses

What is a retrovirus?

A RNA virus that makes DNA from RNA using an enzyme called reverse transcriptase.

What causes AIDS?

Human Immunodeficiency Virus (HIV) causes Acquired Immune Deficiency Syndrome (AIDS), an RNA virus that attacks the immune system.

How does HIV resemble other viruses?

Outwardly,HIV looks like mumps or flu viruses; it has an envelope that helps it enter and exit host cells.

How is HIV different from mumps or flu virsues?

HIV is a retrovirus, it converts RNA—>DNA using reverse transcriptase and integrates into host DNA for reproduction.

What does reverse transcriptase do in retrovirus?

Uses the viral RNA as a template to make a DNA strand, then adds a second complementary DNA strand to form double-stranded viral DNA.

What happens when Viral DNA integrates into the host chromosome?

The viral DNA becomes a provirus one it inserts itself into the host genome.

-A provirus is viral DNA that has been inserted into the host cell’s chromosome where it can remain inactive or later make new viruses

-Explains how and why some viruses stay hidden in your cells for a long time

How does a provirus produce new viruses?

Occasionally, it is transcribed into RNA, which is then translated into viral proteins.

How are retroviruses assembled and released?

Viral RNA and proteins assembled into new virus particles,which then leave the host cell to infect other cells.

Reproductive Cycle of retroviruses?

1)RNA—>DNA via reverse transcriptase

2) Integration into host DNA—→provirus

3)Transcription—→RNA

4)Translation—→Viral proteins

5)Assembly—→new viruses

6)Release—→infect other cells

How HIV damages the immune system?

HIV infects and kills several types of white blood cells. The loss of these cells ,makes the body susceptible to infections it would normally fight off.

When was AIDS first recognized and what causes death in it?

AIDS was first recognized in 1981.

—Opportunistic infections that the weakened immune system cannot fight,leading to syndromes that eventually kill.

How progression of AIDS is slowed?

Two categories of anti-HIV drugs, both of which interfere with viral reproduction

—Protease inhibitors:block enzymes called proteases, which help produce the final versions of HIV proteins

— Reverse transcriptase inhibitors (AZT): block the action of reverse transcriptase preventing viral RNA from being converted into DNA

How does AZT work?

Mimics Thymine in DNA, binds to reverse transcriptase, but cannot be added to DNA, blocking HIV DNA synthesis and stopping viral reproduction

Common treatment strategy for HIV in industrialized countries?

Mainly patients take a drug cocktail, both reverse transcriptase AND inhibitors and protease inhibitors,which is more effective than using either alone.

—Lower death rate by 80%

Can HIV be completely eliminated from the body with drugs?

No. Even with combo therapy,the virus remains and reproduction and AIDS symptoms return if treatment is stopped?

What is a prion?

Infectious protein that is a misfolded form of a normal brain protein;unlike viruses,prions contain no DNA or RNA.

How do prions cause disease?

Prions convert normal proteins into misfolded forms,which clump together and disrupt function

Prion diseases:Scrapie (sheep),chronic wasting (deer/elk), mad cow disease (cattle).

Why mad cow disease is dangerous in terms of detection?

Prions can incubate for at least 10 years before symptoms appear,making it hard to identify sources of infection in time.

What are emerging diseases?

Viruses that suddenly appear or come to the attention of medical scientists.

—Zika,West Nile,Ebola,Avian Flue,H1N1 flu,AIDS (HIV)

How can viruses evolve into a more dangerous from?

Viruses undergo natural selection. RNA viruses mutate rapidly because RNA lacks error-correcting mechanisms, creating strains that can infect previously resistant people.

How Viral diseases spread from one host species to another?

¾ of new human diseases come from animals. Humans can be infected when they hunt,live near,or raise livestock, as in HIV originating from chimpanzees. Mutations in humans can create strains that outcompete others.

How viral diseases from isolated populations lead to epidemics?

Diseases in small, isolated populations can spread widely,especially when factors like international travel,drug use,sexual activity or delayed response are present.

-AIDS spread globally after decades of being unnoticed.