Cell Division and Reproducing New Organisms Science 9

Regeneration Regeneration is the ability to regrow a tissue, an organ or a part of the body Humans are only capable of re-growing tissue and skin Animals with little cell specialization are capable of reproducing an entire organism – this is called fragmentation As cells become more specialized, the ability to grow “replacement parts” becomes limited

Specialization and DNA The nucleus of every cell in the human body contains a complete code for all your characteristics and all cellular functions Every cell contains identical DNA Every cell, however, uses different parts of the DNA because they are directed by different genes Specialized cells only use parts of their genetic information

Stem Cells Skin, bone marrow and other tissues contain stem cells These cells are capable of continuous dividing and may be able to differentiate into different specialized cells They may be activated by an injury or disease

Cloning Cloning is a natural process Asexual reproduction is an example of cloning It is the process of forming identical offspring from a single cell or tissue

Cloning Plants Cells that are capable of reproducing quickly are given hormones to encourage even faster cell division They then transferred from the area where the hormone is and growth slows down Cells begin to specialize and the plant begins to form Delaying specialization appears to be the key in successful plant cloning

Cloning Animals The nucleus is removed from an unfertilized egg cell A nucleus from an embryo (reproducing cells of a fertilized egg from sperm) is inserted into the egg cell The cell continues to divide, much like a fertilized egg, and begins to grow into an organism In order for cloning to work, dividing cells cannot begin to specialize

Mammals and Cloning Mammalian cells have been successfully cloned They were only successful when the nucleus used came from a cell that was very early in its division (8 cells) However, the cloning of a sheep named Dolly changed this Udder cells were taken from one sheep (Finn Dorset) Egg was taken from another sheep (Poll Dorset) and its nucleus was removed The two cells fused and began to reproduce Cell mass was transferred back into the uterus of another sheep (Blackface) Clone is born that has the genetic markings of the Finn Dorset