Duncan blogs an essay: A short history of the genetic alteration of animals.

A Short History of the Genetic Alteration of Animals

 

The first-time humans changed or altered the look and genetic makeup of a species of animals was longer ago than you might think. It happened at least ten thousand years ago when early man first domesticated the wolf

There is big debate when humans first domesticated the wolf and it became more like the dogs we have today. Bones ae being dug up all around the globe, each changing our perception on when the shift happened.

The things is, is that the wolf of today, sharing over 90% of its DNA with our dogs is a different animal from the one which early man domesticated years ago.

Attempting to reconstruct the dog’s lineage through the phylogenetic analysis of DNA sequences from modern dogs and wolves has given conflicting results for several reasons. Firstly, studies indicate that an extinct Late Pleistocene wolf is the nearest common ancestor to the dog, with modern wolves not being the dog’s direct ancestor.

Secondly, the genetic difference between the dog and modern wolves occurred over a short period of time, so the time that the changes took place is difficult to date. This is complicated further by the cross-breeding that has occurred between dogs and wolves since domestication.

Finally, there have only been tens of thousands of generations of dogs since domestication, so that the number of mutations between the dog and the wolf are few and this makes the timing of domestication difficult to date.

 

The famous biologist Charles Darwin noted that breeding lead to ‘striking differences between farm animals and plants when compared to their wild counterparts’.

An example of this is the turkey. Wild Turkeys were first domesticated by the indigenous people of Mesoamerica at least 2,000 years ago.

Because male turkeys are as heavy as 50 pounds, most of the breeding on farms is done through artificial insemination. Up until the 1930s turkeys weighed about 13 pounds, but now weigh in at around 30 pounds.

Turkey farmers began to selectively breed them for both size and speed of growth—especially in the breast, being the highest quality meat on the bird. This shows that the men and women could not have been taking kill from other animals or eating those that had died of natural causes. They were actually selecting and killing what they wanted.

This shows how mankind was manipulating species to make them bigger, meatier and to develop at a faster pace. For instance, the Belgian blue bull has twice the muscle mass of its ancestors.

A modern meat chicken weighs up to three kilograms; almost double the size of a chicken from 60 years ago. But human bread animals not just for meat.

The sheep, originally from Mesopotamia, tamed by humans from around 9 to 11,000 BC. We brought on many changes for the sheep;

They developed more wool and less hair. The colours changed from brown to whites and black. Their ears became more of a lop ear than an erect ears and their horns that the wild sheep possessed were weakened and disappeared from many breeds. Their tails were more floppy and had less vertebrates or bones than the sheep do now, and gradually their brain became smaller. So, they weren’t always the dumb and scared animals which they are commonly portrayed to be.

 

A modern day example of this is the salmon. In 2013, US authorities began discussion to grant approvals for the world’s first genetically modified fish, the Aquabounty salmon, which has had its genes altered so that it grows twice as fast as a normal fish.

Aquabounty salmon is produced through the insertion into the eggs of wild Atlantic salmon of a growth hormone gene from Chinook salmon, as well as a gene from a different type of fish called the ocean eelpout.This makes the salmon produce growth hormone all year round, rather than just during the warmer months.

Since then US heath regulators cleared the way for it to be farmed for human consumption. Like the wild turkey and cow, the salmon were bred to meet the demand, since they do not grow fast in the wild.

The cheapest form of altering genes in CRISPR

It stands for Clustered Regularly Interspaced Short Pallindromic Repeats, which refers to a sequence of base pairs found on the DNA of bacteria that have this feature.

Some bacteria and archaea use CRISPR for adaptive immunity, in order to incorporate bits of DNA from invading viruses into segments of their own DNA in order to target their immune system at those sequences.

Cas refers to CRISPR-associated genes. Cas9 is a specific endonuclease that can cleave DNA. It can be combined with specific RNA in a system that can either insert or delete genetic sequences into the target DNA.

What all of this means is that the CRISPR system can be used for highly specific and convenient gene editing, either deleting or inserting sequences into target genes, or turning those genes off.

CRISPR technology is already proving to be a powerful research tool, and has been adopted by labs around the world.

For instance A small lab with modest funding can use CRISPR to, for example, turn off a gene in a target species (from bacteria to mice) and then study the effects in order to understand what the gene does.

This promises to accelerate our understanding of genes which will likely have tremendous downstream effects.

CRISPR can also be used to create genetically modified organisms. Researchers have used CRISPR technology to create genetically modified mosquitoes that are resistant to malaria. The same procedure can be used to stop other disease and cancer. By altering the genes, turning some off and adding and removing them

 

Every ten minutes, a person is added to the national waiting list for organ transplants. And every day, 22 people on that list die without the organ they need.In the lab of Lars Burdorf at the University of Maryland School of Medicine, they have managed to make a pair of pig’s lungs able to filter human blood.

The problem is, is that dangerous viruses to humans are in the blood the has been filtered through the lungs, harmless to pigs, less so for us.

So there is much to do before these can be put into a human but it is getting there.

Duncan Morrison