Monday, 4 May 2015

Cloned animals

From 1996 (the year in which Dolly was born) to the present day, more than 20 animal species have been succesfully cloned.

Cumulina's second birthday
On October 3, 1997 was born a mouse named Cumulina, cloned for scientific purposes, which was the first animal cloned from adult cells that survived to adulthood. It was a common house mouse from the species "Mus Musculus". It was given that name after the cumulus cells because the nucleus of one of this cells was used to clone it. This nucleus from one mouse was injected through a tiny needle into an egg donated by a second mouse. The egg's original genetic material was removed. Cumulina was healthy all it's life, except for a skin tumor (that is common in mice) it had when it was 23 months, but it was successfully removed. She produced two litters which didn't seem to have suffered any ill effects from the mother's origin as a clone. In May 5 of 2000 , the mouse died of natural causes when it was two years, seven months old (about seven months above the average for her species).
Dr. Ryuzo Yanagimachi, head of "Project Yana" that produced Cumulina said: "We celebrated her first and second birthdays, I didn't expect a third birthday. She was special and was the only one given a name. The others have numbers."

Rainbow, Allie and CC. (From left to right)
Later, on December 22 of 2001, the first cloned cat was born. The cat, named CC (abbreviation for Copycat), was successfully cloned by a group of scientists in Texas. Out of 87 implanted cloned embryos, CC was the only one to survive. She was cloned by transplanting DNA from Rainbow, a female three-colored cat, into an egg cell whose nucleus had been removed, and then implanting this embryo into Allie, the surrogate mother. However she is not identical to her DNA donor because the pattern on cats' coats is only partly genetically determined.
In their first attempt to clone a cat, researchers obtained the cells used to make the clone from the skin cells of a donor cat. Eggs from other cats were used for the next step. Their chromosomes were removed and replaced with the DNA from the frozen cells, creating cloned embryos which were then transplanted into surrogate mothers. It resulted in cloned embryos that were transferred into seven recipient females. Only one cat became pregnant, with a single embryo. But this pregnancy was miscarried and the embryo was surgically removed after 44 days.
In the next attempt the scientists tried using cells from ovarian tissue to receive the DNA from the cat to be cloned. Five cloned embryos that were made in this way were implanted into a single surrogate mother. Pregnancy was confirmed by ultrasound after 22 days and CC was delivered 66 days after the embryo was transferred. The kitten was vigorous at birth and appeared to be completely normal.
The announcement of the successful cat cloning was not given until the animal had completed its shot series and its immune system was fully developed.

On 2003, a female horse was born in Italy from his surrogate mother, it was the first cloned horse and the first to be cloned and carried by its cloning mother (which was not planned and just a coincidence). The researchers technique was to fuse the nuclei of skin cells taken from one male Arabian thoroughbred horse and a one Haflinger mare with eggs taken from slaughtered abattoir horses and emptied of their own DNA. With this technique, they created 841 successfully reconstructed male and female embryos. Of that 841 embryos just eight male and fourteen female embryos developed after seven days of culture. And of the 17 embryos inserted into the mares, only four lead to pregnancies. The horse, called Prometea was born after 336 days and was the only one to survive. The researchers said that a possible application for this techniques could be breeding from castrated male horses that achieve success so the clone could then be used as a stud.

Tai and Snuppy. (From left to right)
The first cloned dog was born by caesarean section after a full 60 days of pregnancy in South Korea on April 25, 2004. The dog, named Snuppy (which stands for "Seoul National University puppy"), was cloned from a cell taken from the ear of a male Afghan hound called Tai
. The reaserchers took the nucleus from the Afghan hound and placed it into an empty egg cell, that was then stimulated to start developing into an embryo that was later transferred to a yellow labrador. The scientists obtained only three pregnancies from more than 1,000 embryo transfers into 123 recipients. Of these three pregnancies, one miscarried and one died soon after birth.
Scientists hope dog clones will help them understand and treat a range of serious human diseases. "The dog has characteristics similar to human beings," told the lead researcher Hwang Woo-suk "some of their diseases are almost the same as human diseases."

On 2012, a cow called Rosita ISA was born in Argentina by caesarean section because of its weigh.
Rosita carried cow genes and  two human genes responsible of some proteins in human milk, and it's able to produce milk really similar to human milk. Rosita was cloned to help fighting infant mortality rate. “Our goal was to raise the nutritional value of cows’ milk by adding two human genes, the protein lactoferrin, which provides infants with anti-bacterial and anti-viral protection, and lysozyme, which is also an anti-bacterial agent.” said Adrian Mutto from the National University of San Martín.

By Juan Carlos Blanco, Paula Blanco, Javier Verde and Laura Corchado.

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