* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cloning
Survey
Document related concepts
Epigenetics wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Epigenomics wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
Primary transcript wikipedia , lookup
Epigenetics in stem-cell differentiation wikipedia , lookup
Microevolution wikipedia , lookup
Molecular cloning wikipedia , lookup
Genetic engineering wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Transcript
Chapter 21 Cloning Cloning Using the somatic cells of a multicellular organism to generate a new organism is called cloning. Each clone is genetically identical to the parent plant. Differentiated cells don’t usually divide in culture, so researchers had to take a different approach to decide if animal cells were totipotent. What Researchers Did… They removed the nucleus of an unfertilized egg and replaced it with one from a differentiated cell. The process is called nuclear transplantation. If the transplanted cell retains all of its genetic information, the recipient cell should develop with all of the necessary tissues and organs. Nuclear Transplantation As these experiments were conducted on frogs, it was determined that something in the DNA does change. In tadpoles, normal development proceeded, but as the age of the donor nucleus increased, the percentage of organisms that developed correctly decreased. Nuclear Transplantation Continued research showed that the DNA remains the same for the most part, but the chromatin changes in a way that problems arise. Nuclear Transplantation Often times, the histones get modified or DNA is methylated and these changes in the chromatin prevent dedifferentiation. Sometimes the process is reversible, but usually it isn’t. One thing is certain, most scientists agree that all cells contain the necessary genetic information to make an entire organism. However, the different cell types exist because of the variations in gene expression. Nuclear Transplanting and Cloning In 1997, Scottish researchers cloned a sheep named Dolly. They used cells from mammary tissue in an adult sheep, implanted the nucleus from the cell into egg cells from which the nucleus had been removed and implanted into the uterus of a lamb. Nuclear Transplanting and Cloning Analysis of the DNA from Dolly showed it was identical to that of the original sheep, and its mitochondria matched that of the mother lamb. However, Dolly’s cells appeared older than her age would indicate. Dolly’s Problems She suffered from a lung disease seen in older sheep. She had arthritis. These results indicate that not all of the DNA had been reprogrammed. Problems With Animal Cloning In General: Many of the animals exhibit a variety of defects such as obesity and premature death. Only a small percentage of the embryos created develop correctly resulting in live birth. Possible reasons for these results include: Epigenetic changes in chromatin (acetylation of histones and/or methylation of DNA) result in only a small number of genes being turned on while the others remain suppressed. Cloning Many plant species and some animal species have natural methods of cloning. Rotifers Strawberries Potatoes Amoeba Hydra 12 Rotiers 13 Rotifera Rotifers are tiny, microscopic animals inhabiting fresh water, marine, and damp soil. Unique because many of them reproduce via parthenogenesis. Parthogenesis With parthenogenesis, females produce offspring from unfertilized eggs. Parthogenesis Some species of rotifers produce two types of eggs. One develops into a female, the other into a short-lived male. The male survives long enough to produce sperm that fertilize the eggs. Parthogenesis Some rotifers produce females. These females lay more unfertilized eggs that develop into more females. Runners Strawberry plants reproduce asexually through their stolons. These stolons are commonly referred to as “runners.” Stolons are stems that grow along the ground or just below it and produce nodes. Stolons periodically produce nodes that can grow roots. 18 Runners The nodes occasionally give rise to roots. If roots grow, a new plant will grown and later produce strawberries. The daughter plants are clones of the original. 19 Tubers Tubers such as potatoes form enlarged stolons. The enlarged stolons develop into storage organs that store nutrients for the formation of a new plant the following year. http://www.potatoes.co.nz/Potato_know_how/ Tubers The tubers have multiple eyes that each generate shoots that can grow into new plants when conditions are favorable. All plants propagated from the same tuber are clones of the parent. 21 http://www.potatoes.co.nz/Potato_know_how/ Budding Budding is a form of asexual reproduction in which a new organism develops from a bud of the original cell. Yeast are fungi that can reproduce by budding. Each new cell that buds off is a clone of the original. http://en.wikipedia.org/wiki/Budding#/media/File:S_cerevisiae_under_DIC_microscopy.jpg Budding Corals, sponges and hydra are common animals that reproduce by budding. Each bud is a descendent of the original and is a clone. http://en.wikipedia.org/wiki/Budding#/media/File:Hydra_oligactis.jpg