what is CRISPR in bacteria and how is this like human immunity?? 

in the human immune system,
when a virus infects us, we produce
antibodies to that specific virus = immunomemory.
When the same virus infects us again, these antibodies recognize the pathogen and can eliminate it. 

Herders who could not longer slaughter and eat meat from their own herds (niestti) lost the traditions associated with their niestti. Sámi make use of all of the reindeer, its organs, antlers, hooves and blood creating material, thread and shoes. Without this source, they had to rely on other sources and government assistance. In one generation, much of the Sami culture has disappeared. 

an odd choice for a vacation...

step 1: making a memory via acquisistion
phage infects a bacterium.
two Cas proteins (Cas1 and Cas2) work together to cut out pieces of the phage DNA and inserts it into one end of the CRISPR array as a new spacer.
A new repeat is also added so all spacers are always flanked by repeats on each side. A memory of the phage is stored. 
Think vaccination!

the lichen, an unassuming symbiote,
​was this tragedy's
​canary...can you think of others?

CRISPR 
​permits the precise modification of DNA sequences within living organisms. 
CRISPR was originally discovered in 1987 as a microbial "immune system" used to recognize and eliminate specific viral pathogens.

step 2: the memory of the phage infection is now in the bacterium's
DNA. Now this DNA memory will be converted into a similar molecule called RNA. The bacterium makes a lot of RNA copies of the phage memory which then roam around the cell. This step is called
CRISPR RNA biogenesis.
The entire array of repeats and spacers is transcribed into a long piece of RNA. Proteins then cut
the long RNA into individual segments each with a spacer and parts of the repeats. These become 
CRISPR RNAs go off and which hunt for matching phage DNA.

Clustered Regularly Interspaced Short Palindromic Repeats

step 3: a phage invades the bacterium. the destruction of invading phage DNA comes next,
a process called interference.

Cas proteins  or a group of Cas proteins grabbing onto or binding one crRNA. Together, the Cas protein(s) plus crRNA form what is known as the search complex, effector complex, or what we’ll call it here — the surveillance complex. (When multiple molecules of protein, RNA, or other components stick to each other and work together, they’re called a complex.)

When a phage injects its DNA into a bacterial cell, the surveillance complex scouts the phage’s genome for a sequence that matches the spacer in its crRNA. This target sequence is called the protospacer. Because the crRNA is a copy of the original phage DNA, it is complementary to, and can form base pairs with, one strand of the DNA injected by another phage of the same species. Base pairs between RNA and DNA look very similar to the ones between each strand of DNA in a normal double helix.

The surveillance complex unzips the phage DNA and checks to see if the crRNA can base-pair with one strand. If the whole spacer can base-pair, it means the surveillance complex has found the target it’s been searching for, so it cleaves the phage DNA to destroy it. If the surveillance complex searches through all the DNA in the cell but doesn’t find a match, it doesn’t make any cuts.

Thousands of reindeer representing almost 90% of the Sami's herds were rounded up and slaughtered, their carcasses buried. 

crispr

when a virus infects a bacterial cell, CRISPR creates a similar immunomemory. the bacterium takes a piece of the virus’s genome and inserts this viral DNA into its own genome. Then the bacterium creates a piece of RNA called guide RNA using the piece of viral DNA. If the same virus infects that bacterium again, this guide RNA can recognize the virus' DNA sequence and destroy it.

the CRISPR acronym... clustered regularly interspaced short palindromic repeats...
 comes from a section of DNA found in the bacterial genome. This DNA is called a CRISPR array or repeat-spacer array. It has two components:
 repeats & spacers.

 Repeats are 30 bp segments of DNA that all have the same sequence.
Each are palindromic...stretch of bases followed by the complementary bases of the same sequence in reverse order. like RACECAR.
this allows the repeats to fold into a hairpin like structure once they’re transcribed into RNA.

Spacers are found between the repeats. Each are small segments of unique phage DNA...the “molecular memory” of a previous infecting virus. These spacers are passed down through generations of bacteria so the individual bacterium doesn’t have to have been infected in order to be immune to a phage. 

let's go step by step...

Many Sami no longer live in the traditional Sami areas, having moved into the towns and cities of Northern Norway. Those who remained in traditional Sami areas now  earn their living working in jobs unfamiliar to the population just one generation ago.