Nuclear transfer is a form of

cloning Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, c ...

. The step involves removing the DNA from an

oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ...

(unfertilised egg), and injecting the

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: * Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

which contains the DNA to be cloned. In rare instances, the newly constructed cell will divide normally, replicating the new DNA while remaining in a

pluripotent Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many thin ...

state. If the cloned cells are placed in the uterus of a

female mammal Female (symbol: ♀) is the sex of an organism that produces the large non-motile ova (egg cells), the type of gamete (sex cell) that fuses with the male gamete during sexual reproduction. A female has larger gametes than a male. Females a ...

, a cloned organism develops to term in rare instances. This is how Dolly the Sheep and many other species were cloned. Cows are commonly cloned to select those that have the best milk production. On 24 January 2018, two

monkey Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomple ...

clones were reported to have been created with the technique for the first time. Despite this, the low efficiency of the technique has prompted some researchers, notably

Ian Wilmut Sir Ian Wilmut, OBE FRS -- FMedSci FRSE (born 7 July 1944) is an English embryologist and Chair of the Scottish Centre for Regenerative Medicine at the University of Edinburgh. He is best known as the leader of the research group that in 1996 ...

, creator of Dolly the cloned sheep, to abandon it.

Tools and reagents

Nuclear transfer is a delicate process that is a major hurdle in the development of cloning technology. Materials used in this procedure are a microscope, a holding

pipette A pipette (sometimes spelled as pipett) is a laboratory tool commonly used in chemistry, biology and medicine to transport a measured volume of liquid, often as a media dispenser. Pipettes come in several designs for various purposes with diff ...

(small vacuum) to keep the oocyte in place, and a

micropipette A pipette (sometimes spelled as pipett) is a laboratory tool commonly used in chemistry, biology and medicine to transport a measured volume of liquid, often as a media dispenser. Pipettes come in several designs for various purposes with diff ...

(hair-thin needle) capable of extracting the nucleus of a cell using a vacuum. For some species, such as mouse, a drill is used to pierce the outer layers of the oocyte. Various chemical reagents are used to increase cloning efficiency.

Microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 1 ...

inhibitors, such as nocodazole, are used to arrest the oocyte in

M phase The cell cycle, or cell-division cycle, is the series of events that take place in a cell that cause it to divide into two daughter cells. These events include the duplication of its DNA (DNA replication) and some of its organelles, and subs ...

, during which its nuclear membrane is dissolved. Chemicals are also used to stimulate oocyte activation. When applied the membrane is completely dissolved.

Somatic cell nuclear transfer

Somatic Cell Nuclear Transfer (SCNT) is the process by which the nucleus of an oocyte (egg cell) is removed and is replaced with the nucleus of a somatic (body) cell (examples include skin, heart, or nerve cell). The two entities fuse to become one and factors in the oocyte cause the somatic nucleus to reprogram to a pluripotent state. The cell contains genetic information identical to the donated somatic cell. After stimulating this cell to begin dividing, in the proper conditions an embryo will develop. Stem cells can be extracted 5–6 days later and used for research.

Reprogramming

Genomic

reprogramming In biology, reprogramming refers to erasure and remodeling of epigenetic marks, such as DNA methylation, during mammalian development or in cell culture. Such control is also often associated with alternative covalent modifications of histones. ...

is the key biological process behind nuclear transfer. Currently unidentified reprogramming factors present in oocytes are capable of initiating a cascade of events that can reset the mature, specialized cell back to an undifferentiated, embryonic state. These factors are thought to be mainly proteins of the nucleus.

References

{{reflist Cloning Developmental biology Cell biology Stem cells Biotechnology Induced stem cells es:Transferencia nuclear celular

Tools and reagents

Somatic cell nuclear transfer

Reprogramming

See also

References