Cloning

CLONING Clones Clones are groups of genetically identical organisms, derived from a single original parent cell • Various methods of cloning exists for animals and plants, while humans can also clone organisms or tissues artificially Animal Cloning Human Cloning Binary Fission • The parental organism divides equally into two clones • Occurs in flatworms (also used by bacteria and protists) Humans can also produce clones via natural mechanisms • Identical twins (monozygotic) are created when fertilised eggs split in two, forming two identical embryos Budding • Cells split off from parent, generating smaller clones • Occurs in Hydra, but is also common to yeast MONOZYGOTIC TWINS Fragmentation • New organisms grow from separated fragment of parent • Common to starfish and some species of annelid worm Zygote splits Parthenogenesis • Embryos formed from an unfertilised (diploid) ova • Occurs in some species of fish, insect, reptile, amphibian Genetically identical Shared placentas Plant Cloning Plants have the capacity for vegetative propagation, whereby small pieces of plant can be induced to grow independently • This is because adult plants possess totipotent meristematic tissue capable of cellular differentiation A stem cutting is a separated portion of a plant stem that is used to regrow a new clone via vegetative propagation Artificial Cloning Embryo Cloning • Animals can be cloned from an embryo by separating the embryonic cells into groups • As embryonic stem cells are pluripotent, each cell can potentially form a cloned offspring • As this method occurs after random fertilization, it is not possible to control the genetic features of potential clones Adult Cloning • Adults can be cloned via the process of somatic cell nuclear transfer (SCNT) • The nucleus is removed from an adult body cell (diploid) and fused with an enucleated egg cell • An electric shock stimulates division of the egg cell and the growing embryo is implanted into a surrogate UV Early embryo (identical cells) Egg cell enucleated Clone Clone Clone Adult cells cultured Nuclei removed