Is it possible to produce clones of animals? Explain how this can occur both naturally and artificially.
When an organism reproduces asexually, its offspring will be its clone. That is because the offspring only receives its DNA from a single parent.
An example of a naturally occurring clone is when a hydra forms a bud. This bud can break off and live independently of its parent. However, it is genetically identical to the parent and therefore a clone. Sponges can also reproduce by budding. Anything that reproduces with a single parent produces identical offspring and thus, a clone. Another example of naturally producing a clone is starfish regeneration. If an arm is removed with a portion of the central disk, it will grow into a complete starfish and is a clone of the original starfish. Binary fission in bacteria and sporulation in molds are also natural ways in which clones are produced of a parent.
Through artificial methods, cloning is also possible. Dolly the sheep was the first successful clone of an adult mammal. This was accomplished in 1996. A donor cell was taken from an adult sheep's udder. This was a diploid cell with a complete genetic blueprint. Next, an egg cell was enucleated, which means its DNA was removed. Using electric shock, the two cells were fused. This cell began to undergo mitotic divisions. The embryo that formed was implanted in a surrogate mother's uterus where it developed into a cloned lamb. This clone was genetically identical to the sheep whose udder cell provided the DNA.
To add to the previous answer, if an organism reproduces sexually, the offspring will never be a clone of its parents. That is because if a sperm and egg nucleus fuse combine DNA, the offspring will have genes from both parents. Therefore, in sexual reproduction, due to independent assortment and recombination of gametes at fertilization, the offspring will display characteristics from each parent and can never be a clone of one.
However, one additional way of producing a clone naturally is when identical twins are produced. One sperm nucleus fuses with one egg nucleus to form a zygote. Mitotic divisions occur forming an embryo. If the embryo splits into two clusters of cells, these will be clones with the same identical blueprint. However, due to environmental influences on genes, even identical twins have slight differences. For example, their fingerprints are unique.