1. DONOR EGG
2. DONOR SPERM
23 Chromosomes When
Removed from the Male Donor
(Cells are called "haploid"
meaning half the chromosomes)
Note: While still in the male body,
sperm contains 46 chromosomes
3. DONOR SPERM INJECTED INTO EGG
EMBRYONIC DEVELOPMENT BEGINS
4. PRO-NUCLEI FORM
69 Chromosomes Present
In Three Bundles:
23 From Sperm
46 From Egg
(23 Will be Discarded Naturally
or may be removed for pro-nuclei
cloning techniques - see below)
5: THE ONE-CELLED EMBRYO IS FULLY FORMED
AND IS CALLED A ZYGOTE
MALE & FEMALE PRO NUCLEI HAVE MERGED
46 CHROMOSOMES NOW PRESENT
HUMAN BEING'S
SEX IS DETERMINED
|
6: EMBRYO BEGINS
TO DIVIDE
CELLS ARE "TOTIPOTENT"- MEANING THEY HAVE THE CAPACITY TO FORM ANY CELL, TISSUE OR ORGAN IN THE HUMAN BODY, INCLUDING NEW EMBRYOS |
7: AT 5-7 DAYS 16 CELLED EMBRYO
DEPICTED - BLASTOCYST
OR INNER MASS HAS FORMED.
TYPICAL
TIMEFRAME TO IMPLANT IN THE WOMB
"INNER
MASS" OF EMBRYONIC STEM CELLS
IS PRESENT
MOST OF THESE CELLS ARE "TOTIPOTENT"
SEPARATION
OF THESE CELLS COULD RESULT
IN THE FORMATION OF (IE) 16 NEW EMBRYOS
MOST
CELLS OUTSIDE THE INNER MASS ARE "PLURIPOTENT" MEANING THEY
CAN FORM MOST, BUT NOT ALL CELLS, TISSUES. THEY CANNOT
FORM NEW EMBRYOS.
THE ABOVE STEPS SHOW HOW AN EMBRYO DEVELOPS. USING THESE SAME PICTURES AS AN EXAMPLE, THE FOLLOWING STEPS EXPLAIN HOW VARIOUS TYPES OF CLONING CAN BE ACCOMPLISHED, INCLUDING "TWINNING" OR THE USE OF GERM LINE CELLS, SOMATIC CELLS OR EVEN THE PRO-NUCLEI TO REPRODUCE A NEW HUMAN BEING.
SOMATIC CELL NUCLEAR TRANSFER - STEP BY STEP IN PICTURES
1) DONOR EGG'S NUCLEUS REMOVED OR "ENUCLEATED" (PICTURE
1)
2) DNA IS TAKEN FROM THE NUCLEUS OF ANY DONOR DNA CELL THAT CONTAINS ALL 46
CHROMOSOMES. THIS COULD BE A SOMATIC* CELL OR A GERM* CELL.
3) DONOR DNA IS INSERTED INSTEAD OF HUMAN SPERM SHOWN IN IVF (PICTURE 2)
4) EGG WITH NEW DNA INSERTED IS ELECTRICALLY OR CHEMICALLY STIMULATED TO BEGIN DEVELOPMENT
AND THEN...
5) NEWLY FORMED ZYGOTE WILL FOLLOW THE EXACT PROCESS OF CELL DIVISION IN
PICTURES 4-7
6) IF THE NEWLY PRODUCED HUMAN BEING IS IMPLANTED IN THE WOMB AND BROUGHT TO FULL TERM, THIS IS
REPRODUCTIVE CLONING. IF THE NEWLY PRODUCED HUMAN BEING IS
DESIRED ONLY FOR HIS/HER STEM CELLS, TISSUES OR FUTURE ORGANS, THE EMBRYO COULD
EITHER BE IMPLANTED AND ABORTED AT THE DESIRED GESTATIONAL PERIOD TO HARVEST
THEM - OR HE/SHE COULD BE DESTROYED IMMEDIATELY TO EXTRACT HIS OR HER EMBRYONIC
STEM CELLS. THE LAST TWO ARE EXAMPLES OF THERAPEUTIC CLONING. THESE
STEM CELLS, TISSUES OR ORGANS MIGHT BE USED IN AN ATTEMPT TO TREAT A DISEASE OR
SIMPLY FOR THE SAKE OF RESEARCH.
*WHEN SOMATIC CELLS ARE USED AS THE DONOR DNA, IT IS CALLED SOMATIC CELL NUCLEAR
TRANSFER; WHEN THE GERM OR REPRODUCTIVE CELLS ARE USED IT IS CALLED GERM LINE CELL NUCLEAR
TRANSFER
IMPORTANT NOTES:
THE MITOCHONDRIAL DNA SHOWN IN THE ORIGINAL EGG IS PASSED INTO THE NEWLY
PRODUCED CLONE. IN ADDITION THE DONOR'S MITOCHONDRIAL DNA IS NOT. THIS
MEANS THERE WILL NEVER BE A "GENETICALLY IDENTICAL" MATCH!
THE HUMAN PRO-NUCLEI DEPICTED IN PICTURE 4 CAN BE INDIVIDUALLY REMOVED AND USED AS DONOR DNA MOLECULES IN ANOTHER ENUCLEATED HUMAN EGG - OR IT CAN BE MIXED WITH OTHER PRO-NUCLEI FROM OTHER HUMANS OR NON-HUMAN ANIMALS. (PRO-NUCLEI TRANSFER IN PICTURES)
THOUGH MOST CELLS ARE "PLURIPOTENT", THE PRIMITIVE GERM LINE CELLS IN 2-3 WEEK OLD EMBRYOS BECOME TOTIPOTENT AGAIN AFTER PARENTAL IMPRINTING IS ERASED AND CAN BE EXTRACTED TO PRODUCE A NEWLY TWINNED EMBRYO. OR THEY CAN BE USED TO FORM SPECIAL GERM LINE PRODUCTS SUCH AS OVARIES, FOLLICLES, ETC. (GERM CELL LINE NUCLEAR TRANSFER)
THOSE CELLS IN THE 2-CELL EMBRYO THROUGH THE BLASTOCYST STAGE THAT ARE "TOTIPOTENT" CAN BE MANUALLY SEPARATED TO FORM NEW EMBRYOS, WHICH ARE TWINS OF THE ORIGINAL, THUS CREATING AN ENDLESS SUPPLY OF EMBRYOS AND STEM CELLS. (BLASTOMERE SEPARATION)
BECAUSE MANY OF THE CELLS IN THE INNER CELL MASS OF THE BLASTOCYST ARE STILL TOTIPOTENT, THE WHOLE EMBRYO CAN BE MANUALLY SPLIT TO FORM NEW TWIN EMBRYOS. (BLASTOCYST SPLITTING)
SOME OF THE BILLS IN THE STATES HAVE ACTUALLY ALLOWED FOR THE IMPLANTATION OF A NEWLY CLONED EMBRYO INTO A WOMAN'S WOMB FOR RESEARCH PURPOSES, AS LONG AS THE CLONED BABY IS NOT BROUGHT TO FULL TERM. THIS MEANS THAT AT ANY TIME UP TO THE NINTH MONTH -EVEN TO THE DAY BEFORE NATURAL BIRTH WOULD OCCUR, THE BABY CAN SIMPLY BE ABORTED TO HARVEST THE BODY PARTS, TISSUES, CELLS ORGANS, ETC.
PRE-IMPLANTATION GENETIC DIAGNOSIS (PGD)
BETTER KNOWN AS EUGENICS
At the 2-4 Day Stage of Embryonic Development, cells can be removed and checked for genetic abnormalities, specific traits or sex selection. If an undesired trait is present or the sex of the baby is not what you wanted, the embryo is destroyed.
Cell Removal & Analysis Using A Micro-manipulator
CONFUSED? NEED ANSWERS? - ASK US!
PLEASE FEEL FREE TO COPY AND REUSE ANY OF THIS MATERIAL
