Cloning | why twins baby born?

Cloning

What is cloning? 

Cloning is the process of forming identical offspring from a single cell or tissue in the
parent organ.

Human clone

A clone originates from a single parent cell, and both the clone and parent have identical (or nearly identical) nuclear DNA. Although some clones show accidental changes in genetic information, cloning does not result in the variation of traits that
would occur with the combination of male and female sex cells.


Cloning is therefore considered a form of asexual reproduction. In fact, clones occur naturally.

Cloning of Hydra

Some species, such as hydra  reproduce by undergoing mitosis to produce buds with identical DNA to the larger parent cell.

In another words, Hydra reproduce asexually by budding. The buds break off to form separate, genetically
identical organisms.

Cloning of plants

The strawberry plant can reproduce asexually by forming genetically identical plantlets on runners.

Cloning in animal

In  animals, offspring with an
identical genetic makeup are sometimes produced when a single fertilized egg undergoes mitosis and the resulting early embryo (called a zygote) then splits in two his results in identical twins. They are also called monozygotic twins, since they
formed from a single zygote.

Fraternal twins are formed when two different eggs are fertilized separately. They are also known as dizygotic twins. Fraternal twins, therefore, are no more genetically similar than are non-twin siblings.

Plant cloning 

In some plants, asexual reproduction is accomplished naturally when a portion of the plant, such as a stem or leaf, breaks off
and develops roots at the base of the broken portion. It is possible for the broken part to become a new plant. This activity
is an example of artificial propagation.



In order to do cloning from plant cutting Perform the following steps  as written in below.

1) Using scissors, carefully cut off the tips of three coleus stems. Cut on an angle. Include several leaves on each stem.

2) Remove a few leaves from the bottom. Put on splash goggles, and wear gloves and/or use tongs to immerse the stem in fungicide.

3) Plant the cuttings in soil.

Plant cloning technology 

In 1958, Fredrick Stewart created great excitement in the scientific world when he revealed that he had produced a plant from a single carrot cell. Today, this technique
is commonly called cloning. Many commercially important plant species, including orchids, are now produced from clones. Unlike plants that arise from sexual reproduction, cloned plants are identical to their parents. This allows production of strains of plants with predictable characteristics.


Not all plant species can be cloned. However, carrots, ferns, tobacco, petunias, and lettuce respond well to cloning, but the grass and legume families do not.


Scientists continue to investigate these differences. Each cell in the cloned plant contains the complete complement of chromosomes from the parent. As the new plant develops, it undergoes mitosis to increase in size.


Some cells then specialize (differentiate) and form roots, stems, or leaves, until a complete plant is formed.

Animal cloning

Cloning a common grass frog using
embryo splitting:


While plant cloning experiments were being conducted, Robert Briggs and Thomas King were busy investigating nuclear transplants in frogs.


 Working with the common grass frog,
the scientists extracted the nucleus from an unfertilized egg cell by inserting a fine glass tube, or micropipette, into the cytoplasm and sucking out the nucleus .


A cell without a nucleus is referred to as enucleated.


A small glass tube, called a micropipette, is used to remove the nucleus from a cell and
later introduce a new nucleus.



Next, the nucleus of a cell from a frog embryo in the blastula stage of development was removed and inserted into the enucleated cell . The egg cell with the transplanted nucleus began to divide much like any normal fertilized egg cell. In later trials, the cell with the transplanted nucleus occasionally grew into an adult frog. The adult frogs displayed the characteristics from the transplanted nucleus.



Careful analysis proved that
the adults were clones of the frog that donated the nucleus. However, different results were obtained when the nucleus was taken from cells at later stages of development.


For example, the nucleus from cells in a later stage, called the gastrula stage, did not bring the enucleated egg from the single-cell stage to the adult. If mitosis occurred at all, it did not progress as far as it did in eggs that received a blastula nucleus. The difference is that the nucleus of a cell in the gastrula stage of development,
unlike a cell in the earlier blastula stage, has specialized. As cells begin to specialize,
they become less able to undergo mitosis.



Cloning a mammal using embryo splitting:



Cloning from adult mammalian cells has proved even more difficult, since they tend
to be highly specialized. Until recently, the only way to get clones was by splitting off cell from a developing embryo.However, cells beyond the eight-cell stage of development seem to be unable to stimulate cell division.


The long-held scientific belief that adult cells cannot be used to clone animals was
disproved with the appearance of a sheep named Dolly. Dr. Ian Wilmut, of the Rosalind Institute in Scotland, extracted the nucleus from an udder cell of an adult Finn Dorsett sheep and placed the nucleus into the enucleated egg cell from a Poll Dorsett sheep. The egg was allowed to develop in a Petri dish until an early embryo stage was reached.



Then this embryo was placed into the womb of a third sheep, a Scottish Blackface. Her genetic information was shown to be identical to that of the Finn Dorsett adult; Dolly was a clone.


Medical experimentation and research could potentially benefit from the availability of cloned animals. For example, experiments on the effectiveness of a drug are often difficult to interpret because of the genetic variation among the individuals tested. If all the test subjects were genetically identical, clearer results could be obtained.


In agriculture, the strongest livestock could be cloned, decreasing farmers’ losses due to disease, and thereby increasing yield. However, many people have moral and ethical problems with this technology and worry about the impact on society .


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