Exam Two Lecture Notes

Exam Two Lecture Notes - 10. Cloning and Stem Cells...

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10. Cloning and Stem Cells Cloning: the process of making identical copies of DNA segments, cells or organisms o DNA replication is a natural cloning process Can be carried out invitro by PCR and splicing human genes or other segments into a DNA vector that multiplies naturally in a host cell (plasmid, virus or artificial chromosome) o Cells naturally clone themselves in cell division and growth (founder cell cell clone (all surviving descendants of the founder cell)) Can label cells invivo by injecting dye into founder cell Grow them invitro by isolating single cells and growing them in individual dishes o Simple organisms naturally clone themselves – you can cut them in pieces and the pieces reconstitute themselves into complete organisms Segments of plant shoots Sponges and polyps o Whole and fertile plants were raised from single cloned cells derived from potato leaves, carrot root phloem, tobacco stem pith – differentiated plant cells are still totipotent Possible to clone animals by transferring nuclei from adult donor cells into enucleated eggs o Sea urchins, salamanders and human monozygotic twins – divide an embryo and you get complete organisms from both halves o Nuclear transfer First developed for frogs and adapted for mammals For cloning vertebrates Donor cells are cultured Unfertilized eggs from the same species are surgically enucleated Nucleus of the donor cell is transferred to the enucleated egg by microinjection or cell fusion Microinjection is too harsh for mammalian eggs, but worked for frogs Cell fusion: done for mammals, electric shock used to go from low energy “sleeping” state to a rapidly dividing embryonic state “activation” Eggs develop in vitro to the blastocyst stage and are transplanted into foster mothers for intrauterine development Done successfully in sheep, pigs, goats, cattle, Rhesus monkeys, cats, and mice using nuclei from different types of cultured cells Dolly, sheep, derived from a cultured udder cell taken from an adult ewe – they used different races of sheep and DNA analysis to show that Dolly was derived from the donor cell o For basic science: Cloning domestic animals allows development of a complete organism based on the nucleus of a differentiated animal cell – shows the cell still carries an undiminished set of genetic information o For pharmacy: Cloning domestic animals helps with drug testing; primates are expensive and ethically problematic; cloning them eliminates genetic variation and allows researchers to get statistically significant data from fewer individuals tested o For agriculture Cloning domestic animals allows individuals with favorable properties to be multiplied exactly and faster than by conventional breeding Cloning Humans o “reproductive cloning” making human babies Couples with one infertile partner could have a child based on nuclear transfer or invitro fertilization using a cloned gamete
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This note was uploaded on 04/07/2008 for the course BIO 346 taught by Professor Kalthoff during the Fall '07 term at University of Texas.

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Exam Two Lecture Notes - 10. Cloning and Stem Cells...

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