#19

Homo sapiens

200,000 ya in Africa, anatomically modern humans

Homo sapiens characteristics

- high forehead
- large braincase
- pronounced chin

Why are homo sapiens sometimes called homo sapiens sapiens?

Due to evidence of intermingling between neanderthals and modern humans, to say homo sapiens would indicate that they were the same species according to the biological species concept. to say homo sapiens sapiens would distinguish homo sapiens as a subspecies

Asia had ___________ DNA

neanderthal

Australia had ___________ DNA

denisovan

Homo sapiens practices

- advanced stone tools
- extensive use of fire
- bows and arrows, projectiles
- produced symbolism and art

What has caused hominin populations to go extinct?

competition, warfare, and intermixing

Tobacco Mosaic Disease

Discovered in the 1800s, stunts the growth of Tobacco plants and gives them a mottled coloration. Confirmed in the 1930s: purified and crystallized

Tobacco Mosaic Virus Experiment

1. Extracted sap from infected plant
2. Passed sap through a porcelain filter known to trap bacteria
3. Rubbed filtered sap on healthy tobacco plants
4. Healthy plants became infected

Virus

A tiny, nonliving infectious particle that invades and then reproduces inside a living cell.

What is a virus made of?

DNA or RNA enclosed by a capsid, and sometimes also a membrane envelope

capsid

protein coat surrounding a virus

membranous envelope

similar to cell membrane, can sometimes surround a virus

capsomere

protein subunits that make up the capsid

adenovirus

covered in glycoproteins

What are the two virus hypotheses?

1. Ancient Virus Origin
2. Cell-First Origin

Ancient Virus Origin

- Viruses coexisted with protocells on early earth
- "Selfish" genetic elements parsitized on independent replicating protocells since early Earth

Evidence of Ancient Virus Origin

- all 3 domains of life can be infected by viruses
- the genomes of most cells contain integrated viral genetic information

Cell-First Origin

- most likely to have happened
- viruses evolved after cells from components of cells capable of exiting the cell
- viruses evolved several times

Evidence of Cell First Origin

- viruses can only replicate within cells
- physical structure and nucleic acids used vary enormously
- mobile genetic elements (plasmids) exist in bacteria

plasmid

A small, circular section of extra DNA that confers one or more traits to a bacterium and can be reproduced separately from the main bacterial genetic code.

viral genome

can be either double or single-stranded DNA or double or single-stranded RNA

bacteria can swap _____ for sexual reproduction

capsids

host range

the limited number of species whose cells can be infected by a particular virus

types of host range

1. broad range
2. narrow range

broad range

can infect many different animals in addition to humans

narrow range

infects a narrower variety of species.

broad range virus example

West Nile: can infect humans, birds, insects

narrow range virus example

malaria, infects umans only

How do viruses infect?

Make use of host enzymes, ribosomes, ATP and other molecules

How do viruses bind to the cell?

Surface molecules on the virus bind to specific host cells "lock-and-key"

bacteriophages

A virus that infects bacteria; also called a phage.

Some of the most complex capsids found among viruses are

bacteriophages

How do phages infect bacteria?

Protein tail piece attaches the phage to the host and injects the phage dna INSIDE

The best understood of all viruses

phaes

Reproductive Mechanisms of Virsues

1. Lytics cycle
2. Lysogenic Cycle

Lytic cycle

a viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses

lysogenic cycle

a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA

the lysogenic cycle includes a ___________ _____________

prophage stage

prophage stage

viral material injects its DNA

lysogenic cycle does not kill the bacterium unless it enters _________

lytic cycle

anti-virus mechanisms

bacteria produce restriction enzymes that recognize and cut up viral phage DNA

restriciton enzymes

cut DNA at specific recognition sequences called restriction sites

CRISPR

Clustered Regularly Interspaced Short Palindromic Repeats

CRISPR function

lead to production of enzymes that cut that specific viral DNA, part of antivirus immune system

CRISPR technology

Derived from bacterial immunity to target and destroy invading viral DNA, often used in gene editing

Example of virus attacking animals

HIV

HIV

human immunodeficiency virus, the virus that causes AIDS

retrovirus

An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.

HIV is a class of

retrovirus

How does someone get AIDS

HIV attacks the white blood cells

HIV characteristics

two viral RNA strands within protein capsid, surrounded by a membrane envelope with glycoproteins which bind to the surface of while blood cells

How does HIV infect a cell?

- the membrane envelope has glycoproteins that bind to the surface of white blood cells
- transcribes its RNA into DNA with reverse transcriptase, and inserts it into the cell
- the new DNA (provirus) becomes a permanent part of the chromosome
- the DNA codes for the production of new RNA and viral protein
- these proteins are assembled into a new virus which leaves the white blood cell

Reverse transcripstase

makes a copy of the RNA

provirus

Viral DNA that inserts into a host genome.

Coronavirus

RNA virus whose membrane envelope is surrounded by surface glycoproteins making it resemble a crown

What type of cell do coronaviruses typically attach to?

animal mucus membrane cells

Genetic material in coronaviruses

Single RNA strand, capsid tightly bound to RNA

Sars-Cov-2

the strain that causes COVID-19

COVID-19 is especially dangerous for

elderly people, those with respiratory issues, or immune system problems

pandemic

an epidemic of disease caused by one viral strain that has spread around the world

How does the immune system react to coronavirus?

The human immune system handles it normally, producing antibodies and memory B cells

Who is more resistant to Sars2/COVID-19?

people who have had previous serious corona infections, including severe cold

_________ do not work on viruses

Antibiotics

Antiviral Drug

can interfere with the virus binding to the cells or to the virus replicating inside the cell

lymphocytes

white blood cells

How do lymphocytes work?

- recognise the antigens on pathogens
- produce antibodies
- antibodies destroy pathogens

vaccine

injects inert/harmless derivative of a pathogen that stimulates a host's immune system to mount defenses against the pathogen

example of immunization vaccine

small pox

memory B cells

a kind of white blood cell that remains in reserve to respond to next infection, ensures that future infection will be counteracted by your own immune system

prions

misfolded proteins that induce normal proteins to be misfolded the same way, inducing a "chain reaction" causing disease

prion example

kuru, mad cow disease

kuru

prion disease in humans that is caused by cannibalism, characterized by breakdown of tissue in brain

BSE/mad cow disease

prions, cattle fed with materials containing cattle meat

what part of the body do prions affect?

attacks the brain