Twins and Cloning Flashcards
Dizygotic/fraternal twins
twins from two zygotes. Caused by two oocytes being ovulated and fertilized. No more genetically similar than other siblings. Behaviorally similar because of similar developmental environments.
Monozygotic twins
twins from a single zygote. Called identical twins. Caused by embryo dividing into two. Generally occurs by blastocyst stage.
Conjoined/Siamese twins
twins that are physically joined. Caused by incomplete separation of monozygotic twins.
mirror image twins
twins with mirrored features. Caused by late twinning. Asymmetry is determined, then reversed at twinning event. External features (handedness) is reversed. Internal organs reversed in one twin.
Somatic cell nuclear transfer (SCNT)
Clones donor of somatic cells.
Honolulu technique
Remove somatic cell nucleus, Remove oocyte nucleus, add somatic cell nucleus to oocyte, promote fusion of a new nucleus and oocyte.
Roslin Technique
Remove oocyte nucleus, Put cells near each other and shock them to promote fusion.
SCNT differences between clone and original
Soul, X-chromosome inactivation pattern (random differences in female clone), uterine environment, mitochondrial DNA, parents
Pronuclear Transfer
Clones zygote. 1 parent contributes nuclear DNA, 1 (Honolulu) or 2 (Rosin) contribute mitochondrial DNA.
Pronuclear Transfer steps
Remove zygote 2 pronuclei, add zygote 1 pronuclei to zygote 2, promote fusion
Maternal spindle transfer
No clone created. 1 parent contributes DNA from sperm, 1 parent contributes form oocyte 2 mitochondria, 1 parent contributes DNA from oocyte 1 nucleus = 3 parents.
Maternal spindle transfer steps
remove oocyte 2 nucleus, add oocyte 1 nucleus to oocyte 2, fertilize new oocyte
Altered Nuclear Transfer (ANT) Steps
Remove oocyte nucleus, alter somatic cell nucleus, add altered somatic cell nucleus to oocyte
ANT purpose
prevent creation of a new organism to ethically harvest stem cells
ANT concerns
may create an organism with a severe disability, research may not be ethically possible.
Chromosome
an organized strand of DNA found in nucleus of the cell Humans have 23 kinds (1 set).
Diploid
having two sets of chromosomes
Tetraploid
having four sets of chromosomes
Tetraploid Complementation steps
Fuse cells of two normal embryos, grow to blastocyst stage, inject stem cells into inner cell mass, grow embryo
tetraploid Complementation
used to confirm potential of injected stem cells. If successful, the stem cells can create all cells of the body.
Reproductive cloning
cloning used for reproduction, Uses SCNT
Therapeutic cloning
cloning used for therapies. Doesn’t use SCNT. Clone is killed to harvest stem cells. Procedure is identical to reproductive cloning.
Human clones
Created using roslin technique. Hybrid (cow oocyte + human nucleus) and Human.