Showing posts with label DNA. Show all posts
Showing posts with label DNA. Show all posts

Tuesday 31 October 2023

Forensics will be able to use cat and dog hairs to help convict criminals

NEWS AND COMMENT: This is an interesting development in the world of forensic science. Until now it's been all but impossible to use cat and dog hairs at a crime scene to help identify the criminal because (1) most cat hairs do not contain a root or it is dead resulting in almost no nuclear DNA sequence and (2) domestic cats have a very small number of ancient ancestors resulting in very similar DNA and therefore it is impossible to separate one from another using, as I understand it, nuclear DNA.


However, a new method of screening uses every part of the mitochondrial DNA which enables the forensic scientist to detect tiny differences and in doing so they will be able to link a domestic cat that lives with the alleged criminal. This will help to convicted criminals.

Obviously, not all criminals live with a domestic cat but in the UK, you will find a domestic cat in 26% of the households. And in those homes, there is invariably a pile of cat and dog hair. It is one of the great bugbears of many pet owners: getting rid of it!

Now it appears that forensic scientists can actually use it and as I understand it, it works like this. The criminal lives with a cat or dog. The criminal commits a crime and leaves behind at the crime scene some cat/dog hairs that have come off his clothes and which are deposited onto the victim or other objects at the crime scene. These are collected and analysed linking the criminal with the crime scene.

Although mitochondrial DNA is less variable than nuclear DNA there is just a 3% chance that two cats share the same genetics in this regard. It will be another tool to use to help pin down the criminal.

And so, forensics will now be able to use those hairs to help convict an alleged criminal. Mark Jobling, Prof of genetics at Leicester University and the co-author of the study said that, "In criminal cases where there is no DNA available to test, pet hair is a valuable source of linking evidence, and our method makes it much more powerful. The same approach could also be applied to other species, and particularly dogs."

The other co-author of the study, Dr. Jon Wetton, also of Leicester University's Department of Genetics and Genome Biology, added that, "If the police have a case where there are cat hairs but no human DNA to link a suspect with a crime it is now likely that, using our approach, we would be able to exclude the great majority of cats as the source and demonstrate a stronger link to the suspect's cat. The approach could be applied to other species, dogs being the most relevant as their hairs are also frequently found on clothing."

The study is published online on the Forensic Science International Genetics website. The abstract (summary) in an earlier study of 2014 states that "Mitochondria DNA is often the only option for DNA analysis of shed hair."

And in that 2014 study the scientists add that analysis of mitochondrial DNA has been accepted in US criminal courts since 1996 which was the date of a murder trial concerning Henry L Polk Jnr. in Mississippi. This was the first legal proceedings in America where cat mitochondrial DNA analysis was produced as evidence.

Initially the court deemed it inadmissible but once the judge had heard the arguments it became admissible.

Mitochondrial DNA versus nuclear DNA


Mitochondrial DNA and nuclear DNA differs in the following ways:
  • Mitochondrial DNA is inherited only from the mother while nuclear DNA is inherited from both parents.
  • Mitochondrial DNA is circular and smaller in size. Nuclear DNA is larger in size and linear.
  • Mitochondrial DNA replicates separately from the nuclear DNA and encodes for proteins that work only for the mitochondria. Conversely, nuclear DNA encodes for proteins that work for the entire cell.
  • Finally, nuclear DNA is found in the cell nucleus while mitochondrial DNA is found in the mitochondria (source Bing AI).
Note: the source of this post is The Telegraph newspaper on MSN. I can't find the study online at this time to allow me to provide a link to it.
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P.S. please forgive the occasional typo. These articles are written at breakneck speed using Dragon Dictate. I have to prepare them in around 20 mins.

Sunday 14 May 2023

FAKE! DNA evidence to prove that big cats prowl British countryside!?

The British news media, at the moment (mid-May 2023), are stating that DNA evidence from a black hair strand caught on a barbed wire fence following a sheep attack has offered "definitive proof" that big cats are roaming the British countryside. Don't believe it. This is fake in my view but I stress this is my opinion.

The picture in the circle is a stock image from Alamy of a genuine black big cat (melanistic) while the blurry one is of a domestic cat crossing a field!
The picture in the circle is a stock image from Alamy of a genuine black big cat (melanistic) while the blurry one is of a domestic cat crossing a field! Image: LBC.

There is a band of people in Britain who have been trying to prove that there are big cats - normally black panthers - roaming around the British countryside surreptitiously and have been for decades.

My suggestion (allegation) is that one of these band of brothers has got hold of a black hair strand from a melanistic jaguar i.e. black panther from a zoo because they have a friend working in the zoo and they have placed this black hair on a barbed wire fence and then commissioned a laboratory to do a DNA test on it. They've worked with the documentary film maker to do this (see below).

That I think is a very fair allegation because there is simply no evidence whatsoever to prove that there are big cats in the British countryside. People have been taking photographs and videos of big cats for decades and they are always fuzzy images and the cats are always domestic cats on analysis.

You have to have an inordinate amount of faith to believe what these big cat conspiracists want us to believe.

The LBC website say that this is a "shocking revelation" (LOL). It comes after a documentary film maker spent years investigating sightings across the country they say.

This mysterious black feline hair strand was recovered from a farm in Gloucestershire where there has been some unusual predatory activity. And there is apparently video footage of a large black animal in the area. They mean a domestic cat.

The picture above published on the LBC website shows a black panther - a genuine black big cat - but it is a stock photograph.

Matthew Everett from Dragonfly Films said:

The DNA was from hairs caught on a barbwire fence where there had been some unusual predatory activity.

"It's taken five years for the production team to find such evidence and film its journey from collection to analysis.

"People in Gloucestershire and Britain have described what appear to be black leopards for decades. So, a leopard DNA result from a black hair sample is unsurprising.

"This is not the first such DNA result and is unlikely to be the last.

"There is a great deal of 'secondary evidence' for these cats, such as consistent witness reports, but hard evidence like DNA is hard to get, so the contribution from this documentary is very helpful.

"Collecting such evidence from local people, farmers and landowners is essential - Citizen Science like this will hopefully help us learn more about the Bagheera type big cats which may be quietly naturalising here."

Dragonfly Films are looking into broadcast options for the documentary film. I will look forward to seeing it. But I do not believe a shred of this. It is an attempt to make an interesting film based upon a topic which has fascinated millions of people for a very long time and upon which the news media depend when real news becomes quiet.

Tuesday 6 July 2021

All Scottish wildcats and kittens should be DNA tested for purebred status

NEWS AND OPINION: There is a nice story about Scottish wildcats today reported by the Daily Record. It concerns three Scottish wildcat kittens at the Five Sisters Zoo in West Calder, near Livingston. On their first medical they discovered that they have two boys and one girl. They look very much like Scottish wildcats with their tabby coats and slightly fierce appearance which is exactly the way you want it. The photograph on this page is from the Daily Record. There next job is to name them and they are looking for suggestions on their Facebook page.

Scottish wildcat kitten at his first medical
Scottish wildcat kitten at his first medical. Photo: Five Sisters Zoo, via the Daily Record.

The report states that there are an estimated 35 Scottish wildcat in the wild in Scotland and that they are 50 times rarer than a giant panda. They may actually be rarer than that. In fact, they may no longer exist in purebred form. There's been so much interbreeding between domestic and feral cats and Scottish wildcats that it is plausible to argue that there are no purebred Scottish wildcats left in captivity or in the wild.

I don't know if any wildcats in zoos are purebred, such as these three darling kittens. I think that zoos should confirm to the public that they are genuine Scottish wildcats with no dilution of their DNA through crossbreeding with non-purebred Scottish wildcats.

Where a wild cat becomes extinct or is becoming extinct through interbreeding with other species of cat, it is beholden upon zookeepers who are in the business of conservation, they state, to make sure that they are caring for the genuine item and not a hybrid. For all I know these beautiful kittens may be hybrids and if they are you can't call them Scottish wildcats. One issue is that the appearance of a Scottish wildcat hybrid is very similar to the genuine article.

CLICK FOR PAGES ON THE EUROPEAN WILDCAT

I don't want to be too negative because it's a nice story but I've seen quite a lot of estimates as to the number of Scottish wildcats left in the wild over the years and they are just that: estimates. This leads me to believe that there may be none left which is a stark realisation.

Although people refer to this species of wild cat as a "Scottish wildcat" it is possibly or probably fairer to call this cat a European wildcat. I don't know whether it is true that there is a subspecies of wildcat called the Scottish wildcat. 

Also, please note that I use the word "wildcat" and the phrase "wild cat" for a specific reason. The phrase "wild cat" refers to any individual cat of any wild cat species whereas the word "wildcat" in my opinion refers to the species which is the 'wildcat'. It is complicated but I'm being particular about this.

Thursday 18 June 2015

Five Female Wildcats Are the Ancestors of All Today's Domestic and Feral Cats

Gabriel and Parakeet

It seems extraordinary but based upon DNA research five female North African wildcats (felis silvestris lybica) are the ancestors of the entire world's approximate 500,000,000 house cats.  To reiterate; the research tells us is that all of today's domestic cats come from just these 5 female North African wildcats.  

The researchers concluded that five females of this species of wildcat made the transition from being wild to being semi-domesticated within settlements where they were safe from predators and where they had a ready supply of rodents as prey which infested the settlers' homes and granaries.

As all the feral cats in the world today come from domestic cats then we have to say that all of the domestic, stray and feral cats on the planet today are descended from five female cats of the species felis silvestris lybica.

The research was carried out by Carlos Driscoll of the US National Cancer Institute and colleagues including David MacDonald of Oxford University. They spent more than 6 years analysing the DNA of wildcats,  purebred cats and house cats.

They discovered that the DNA of all house cats (including of course purebred cats) fall within the DNA cluster of the Near Eastern wild cat.  This made this subspecies of wildcat the ancestor of the domestic cat.

Source: NY Times June 29th 2007. The photo is of my tabby cat in whom you can see the North African wildcat ancestor!



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