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Thursday, September 23, 2010

8.27 Cloning Explained Exactly/Pregnancy Prevention

Physician's Notebooks 8 - http://physiciansnotebook.blogspot.com - See Homepage

Obstetrics and Birth Control Section Update 7 April 2018

27. Cloning Explained
Our own consciousness is transient, and memories of it will not much outlast each one of our deaths. But parts of the DNA patterns in egg and sperm may go on; these are derived from DNA that goes back a billion years to first cellular life evolved in the primeval ooze, and for those who will have fruitful offspring, the DNA will continue into the future.
   One’s body expresses a particular DNA pattern at an instant in cosmic time. The person I visualize cherishing Physician’s Notebooks should focus on passing on her or his DNA patterns, with best nurturing, forward to help shape Earth's and the Cosmic future.
   Every ovum (pl. ova) is already developed inside an unborn baby. Cells that become ova migrate from upper part of abdomen in 4-month female fetus and each one burrows into an ovary, to form a tiny cystic nest surrounded by cells that secrete nourishing fluid. Then each does two unequal splits producing 4 daughter cells, only one of which becomes the ovum. Three of the 4 daughter cells donate most of their stuff to the clone mate that will become the ovum.
   When we consider that there are hundreds of thousands of undeveloped ova in both ovaries at birth and that ovulation occurs c.300 times in a woman's lifetime to produce 2 or 3 new persons (in developed country), we can see the tremendous loss of ova to pass on the DNA.
   Rearrangement of the DNA during the 2 cell divisions forming an ovum ensures that every ovum is unique. Identical twins develop from a single ovum that is fertilized by a single sperm and, in the identical twins the 1st cell division after the fertilization, splits into two exact copies of the fertilized ovum. But other twins and higher multiple births are due to fertilization of separate ovum by separate sperm during a single cycle and therefore are not identical and are not much different from siblings born on different dates.
   An identical twin differs from its twin mate because of the differences in each one's environment. (Includes nurturing and child raising)
Also to be considered is the mitochondria DNA which is passed on to next generation as 37 mitochondrial genes in each of the many mitochondria in the cytoplasm of the ovum and therefore is a maternal genetic affect.
   Artificial cloning starts with making an ovum pop out of an ovary (by ovulation medicine), removing its nucleus and keeping the rest of the cell intact and inserting a donor diploid nucleus. (Taken from non-gamete cell, eg, scraped from inner cheek or skin and having paired chromosomes, in human 23 pairs, or total 46, which is diploid state compared to the 23 singles of chromosomes in a human ovum or sperm, which is haploid state) This combination cell (The new clone cell is composed of a donor nucleus with the diploid chromosomes, inside an ovum cytoplasm) is then stimulated to start dividing chemically or by micro pin prick, then grown in a Petri dish or test-tube into early stage embryo, then implanted into a receptive uterus (may be of a surrogate mother), and the pregnancy develops to the birth of a human that is the result of a cloning.
   Popular imagination has a cloned offspring as being exact copy of its nuclear donor but it is not exactly so. If the ovum cytoplasm comes from another person different from the donor nucleus, a person that is female, there will be a 5% difference in DNA due to the mitochondria DNA in the ovum cytoplasm. The closest copy clone occurs when the nucleus donor is the same woman who produced the ovum that is cloned and the resulting embryo of the clone is put into her uterus. And if such a clone is raised to adulthood as close as possible to the way her mother was raised, we would see a near exact person copy. In all cases there will be non-genetic differences between clone offspring and donor if each was developing in different uterus environments or brought up separately. But the body features would be very alike.
   One use of human cloning would be for men or women who are permanently childless for reason other than defect in chromosome to pass on his or her own cellular chromosome DNA in offspring. Another - more fictional than real -  might be a “replacement person”, say your beloved dies young?  Then her suspended animation clone is taken out of deep-freeze and animated and trained to be her replacement.
   Cloning is here today and also a potential future in our world.

End of Chapter. To read next now, click 8.28 To Get Pregnant or Not/Artificial Insem./IVF...








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