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The first cloned animal was Dolly, a sheep who was born in 1996. The success rate of reproductive cloning at the time was very low. Dolly lived for seven years and died of respiratory complications ( [link] ). There is speculation that because the cell DNA belongs to an older individual, the age of the DNA may affect the life expectancy of a cloned individual. Since Dolly, several animals such as horses, bulls, and goats have been successfully cloned, although these individuals often exhibit facial, limb, and cardiac abnormalities. There have been attempts at producing cloned human embryos as sources of embryonic stem cells, sometimes referred to as cloning for therapeutic purposes. Therapeutic cloning produces stem cells to attempt to remedy detrimental diseases or defects (unlike reproductive cloning, which aims to reproduce an organism). Still, therapeutic cloning efforts have met with resistance because of bioethical considerations.

Art connection

To clone Dolly the sheep, a Scottish Blackface sheep was used as a cytoplasmic donor. Eggs from this sheep were extracted, and the nucleus removed. A Finn-Dorset sheep was used as the nuclear donor. Nuclei were extracted from mammary cells, and direct electric current was used to fuse the nuclear DNA with the donor egg. The egg was then allowed to divide to the blastocyst stage, in which a sphere of cells contains a cluster of cells on one side. The blastocyst was implanted in a surrogate mother, resulting in Dolly the sheep.
Dolly the sheep was the first mammal to be cloned. To create Dolly, the nucleus was removed from a donor egg cell. The nucleus from a second sheep was then introduced into the cell, which was allowed to divide to the blastocyst stage before being implanted in a surrogate mother. (credit: modification of work by "Squidonius"/Wikimedia Commons)

Do you think Dolly was a Finn-Dorset or a Scottish Blackface sheep?

Genetic engineering

Genetic engineering is the alteration of an organism’s genotype using recombinant DNA technology to modify an organism’s DNA to achieve desirable traits. The addition of foreign DNA in the form of recombinant DNA vectors generated by molecular cloning is the most common method of genetic engineering. The organism that receives the recombinant DNA is called a genetically modified organism (GMO). If the foreign DNA that is introduced comes from a different species, the host organism is called transgenic    . Bacteria, plants, and animals have been genetically modified since the early 1970s for academic, medical, agricultural, and industrial purposes. In the US, GMOs such as Roundup-ready soybeans and borer-resistant corn are part of many common processed foods.

Gene targeting

Although classical methods of studying the function of genes began with a given phenotype and determined the genetic basis of that phenotype, modern techniques allow researchers to start at the DNA sequence level and ask: "What does this gene or DNA element do?" This technique, called reverse genetics, has resulted in reversing the classic genetic methodology. This method would be similar to damaging a body part to determine its function. An insect that loses a wing cannot fly, which means that the function of the wing is flight. The classical genetic method would compare insects that cannot fly with insects that can fly, and observe that the non-flying insects have lost wings. Similarly, mutating or deleting genes provides researchers with clues about gene function. The methods used to disable gene function are collectively called gene targeting. Gene targeting is the use of recombinant DNA vectors to alter the expression of a particular gene, either by introducing mutations in a gene, or by eliminating the expression of a certain gene by deleting a part or all of the gene sequence from the genome of an organism.

Questions & Answers

how does meiosis produced
Kauzi Reply
what are structure of the cell
wana Reply
what did Darwin say about evolution
Hope Reply
effect of planning beans of using fertilizer
Elizerbeth Reply
what do we mean by transgenic organisms?
FADILAT Reply
what is or are the functions of the Islets of Langarhaans
FADILAT
They are the regions of the pancreas that contains the endocrine cell
Iyadi
is the studly of life
Aisha Reply
what is biology
Asunta Reply
is the study of living organism and their interection with one another and their environment.
Belbon
what is soil
Mukisa Reply
the top layer of the earth in which plant's, tree's
Ahmad
type of soil
Asunta
function of cell wall
Nthati Reply
function of cell wall
Asunta
To protect the cell from bursting
Maurice
to protect the cell from bursting
Deborah
to protect all other internal components of the cell
Olaoye
What is escherichia coli
Tumise Reply
It's an example of gram negative Bacteria
Abdulrasheed
in what type of cells is meiosis taking place?
Rhyeann Reply
sex cells
Eric
hlo
Amit
reproductive system of earthworm plzz describes
Amit
procryotic cell and some eucaryotic cell
Olaoye
Reproductive or sex cells
Abdulrasheed
applications of biology
Namawejje Reply
what is dormancy?
Aliyu Reply
hello guys what's the difference between prokaryotes and eukaryotes
Nwachukwu Reply
hlo what are the applications of biology?
Namawejje
eukaryotic cells have DNA in their nucleus while prokaryotic cells have their DNA present freely in their cytoplasm.
FADILAT
deviation from mendelian
Ogali Reply
what is lethal allele
Ogali
a lethal allele is an allele that can cause poor development or even death of an organism
Olaoye

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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