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Old 03-10-2006, 03:31 PM   #90
Samuel Dravis
 
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Quote:
Originally Posted by jmac7142
Actually, biologists classify something as a living thing when the fulfill the following conditions:

1. Cellular Organization: All living things are made of one or more cells.
2. Metabolism: The sum of all chemical reactions that an organism carries out. All living things use energy to grow, to move, and to process information.
3. Homeostasis: The process whereby all living things maintain relatively stable internal conditions. (For example, your body maintains a temperature of about 37∞C (98∞C) no matter how cold or warm the weather is.)
4. Reproduction: The ability to reproduce from one generation to the next is characteristic of all species of living things.
5. Heredity: A process whereby living things pass on genes during reproduction. All living things have DNA molecules inside their cells that encode information to direct growth and development – a set of blueprints, called genes.


Therefore sperm are not living beings, and fetuses are not living beings.
Try telling an eunuch he is not alive. Will you take away his human rights because he does not have a way to reproduce? Are you trying to say it's ethical to kill someone based solely on their ability to reproduce? What?

I agree, sperm and eggs are not human beings. They have potential if they're in the right place at the right time, but they are destroyed when they create the zygote:

To begin with, scientifically something very radical occurs between the processes of gametogenesis and fertilization — the change from a simple part of one human being (i.e., a sperm) and a simple part of another human being (i.e., an oocyte — usually referred to as an "ovum" or "egg"), which simply possess "human life", to a new, genetically unique, newly existing, individual, whole living human being (an embryonic single-cell human zygote). That is, upon fertilization, parts of human beings have actually been transformed into something very different from what they were before; they have been changed into a single, whole human being. During the process of fertilization, the sperm and the oocyte cease to exist as such, and a new human being is produced.

To understand this, it should be remembered that each kind of living organism has a specific number and quality of chromosomes that are characteristic for each member of a species. (The number can vary only slightly if the organism is to survive.) For example, the characteristic number of chromosomes for a member of the human species is 46 (plus or minus, e.g., in human beings with Down's or Turner's syndromes). Every somatic (or, body) cell in a human being has this characteristic number of chromosomes. Even the early germ cells contain 46 chromosomes; it is only their most mature forms — the sex gametes, or sperms and oocytes — which will later contain only 23 chromosomes.1 Sperms and oocytes are derived from primitive germ cells in the developing fetus by means of the process known as "gametogenesis." Because each germ cell normally has 46 chromosomes, the process of "fertilization" can not take place until the total number of chromosomes in each germ are cut in half. This is necessary so that after their fusion at fertilization the characteristic number of chromosomes in a single individual member of the human species (46) can be maintained — otherwise we would end up with a monster of some sort.

To accurately see why a sperm or an oocyte are considered as only possessing human life, and not as living human beings themselves, one needs to look at the basic scientific facts involved in the processes of gametogenesis and of fertilization. It may help to keep in mind that the products of gametogenesis and fertilization are very different. The products of gametogenesis are mature sex gametes with only 23 instead of 46 chromosomes. The product of fertilization is a living human being with 46 chromosomes. Gametogenesis refers to the maturation of germ cells resulting in gametes. Fertilization refers to the initiation of a new human being.

1) Gametogenesis

As the human embryologist Larsen2 states it, gametogenesis is the process that converts primordial germ cells (primitive sex cells) into mature sex gametes — in the male (spermatozoa, or sperms), and in the female (definitive oocytes). The timing of gametogenesis is different in males and in females. The later stages of spermatogenesis in males occur at puberty, and continue throughout adult life. The process involves the production of spermatogonia from the primitive germ cells, which in turn become primary spermatocytes, and finally spermatids — or mature spermatozoa (sperms). These mature sperms will have only half of the number of their original chromosomes — i.e., the number of chromosomes has been cut from 46 to 23, and therefore they are ready to take part in fertilization.3

Oogenesis begins in the female during fetal life. The total number of primary oocytes — about 7 million — is produced in the female fetus' ovaries by 5 months of gestation in the mother's uterus. By birth, only about 700,000 - 2 million remain. By puberty, only about 400,000 remain. The process includes several stages of maturation — the production of oogonia from primitive germ cells, which in turn become primary oocytes, which become definitive oocytes only at puberty. This definitive oocyte is what is released each month during the female's menstrual period, but it still has 46 chromosomes. In fact, it does not reduce its number of chromosomes until and unless it is fertilized by the sperm, during which process the definitive oocyte becomes a secondary oocyte with only 23 chromosomes.4

This halving of the number of chromosomes in the oocytes takes place by the process known as meiosis. Many people confuse meiosis with a different process known as mitosis, but there is an important difference. Mitosis refers to the normal division of a somatic, or germ cell in order to increase the number of those cells during growth and development. The resulting cells contain the same number of chromosomes as the previous cells — in human beings, 46. Meiosis refers to the halving of the number of chromosomes that are normally present in a germ cell — the precursors of a sperm or a definitive oocyte — in order for fertilization to take place. The resulting cells have only half of the number of chromosomes as the previous cells — in human beings, 23.

One of the best and most technically accurate explanations for this critical process of gametogenesis is by Ronan O'Rahilly,5 the human embryologist who developed the classic Carnegie stages of human embryological development. He also sits on the international board of Nomina Embryologica (which determines the correct terminology to be used in human embryology textbooks internationally):

"Gametogenesis is the production of [gametes], i.e., spermatozoa and oocytes. These cells are produced in the gonads, i.e., the testes and ovaries respectively. ... During the differentiation of gametes, diploid cells (those with a double set of chromosomes, as found in somatic cells [46 chromosomes]) are termed primary, and haploid cells (those with a single set of chromosomes [23 chromosomes]) are called secondary. The reduction of chromosomal number ... from 46 (the diploid number or 2n) to 23 (the haploid number or n) is accomplished by a cellular division termed meiosis. ... Spermatogenesis, the production of spermatozoa, continues from immediately after puberty until old age. It takes place in the testis, which is also an endocrine gland, the interstitial cells of which secrete testosterone. Previous to puberty, spermatogonia in the simiferous tubules of the testis remain relatively inactive. After puberty, under stimulation from the interstitial cells, spermatogonia proliferate ... and some become primary spermatocytes. When these undergo their first maturation division (meiosis 1), they become secondary spermatocytes. The second maturation division (meiosis 2) results in spermatids, which become converted into spermatozoa."6

"Oogenesis is the production and maturation of oocytes, i.e., the female gametes derived from oogonia. Oogonia (derived from primordial germ cells) multiply by mitosis and become primary oocytes. The number of oogonia increases to nearly seven million by the middle of prenatal life, after which it diminishes to about two million at birth. From these, several thousand oocytes are derived, several hundred of which mature and are liberated (ovulated) during a reproductive period of some thirty years. Prophase of meiosis 1 begins during fetal life but ceases at the diplotene state, which persists during childhood. ... After puberty, meiosis 1 is resumed and a secondary oocyte ... is formed, together with polar body 1, which can be regarded as an oocyte having a reduced share of cytoplasm. The secondary oocyte is a female gamete in which the first meiotic division is completed and the second has begun. From oogonium to secondary oocyte takes from about 12 to 50 years to be completed. Meiosis 2 is terminated after rupture of the follicle (ovulation) but only if a spermatozoon penetrates. ... The term 'ovum' implies that polar body 2 has been given off, which event is usually delayed until the oocyte has been penetrated by a spermatozoon (i.e., has been fertilized). Hence a human ovum does not [really] exist. Moreover the term has been used for such disparate structures as an oocyte and a three-week embryo, and therefore should be discarded, as a fortiori should 'egg'."7 (Emphasis added.)

Thus, for fertilization to be accomplished, a mature sperm and a mature human oocyte are needed. Before fertilization,8 each has only 23 chromosomes. They each possess "human life," since they are parts of a living human being; but they are not each whole living human beings themselves. They each have only 23 chromosomes, not 46 chromosomes — the number of chromosomes necessary and characteristic for a single individual member of the human species. Furthermore, a sperm can produce only "sperm" proteins and enzymes; an oocyte can produce only "oocyte" proteins and enzymes; neither alone is or can produce a human being with 46 chromosomes.

Also, note O'Rahilly's statement that the use of terms such as "ovum" and "egg" — which would include the term "fertilized egg" — is scientifically incorrect, has no objective correlate in reality, and is therefore very misleading — especially in these present discussions. Thus these terms themselves would qualify as "scientific" myths. The commonly used term, "fertilized egg," is especially very misleading, since there is really no longer an egg (or oocyte) once fertilization has begun. What is being called a "fertilized egg" is not an egg of any sort; it is a human being.

2) Fertilization

Now that we have looked at the formation of the mature haploid sex gametes, the next important process to consider is fertilization. O'Rahilly defines fertilization as:

"... the procession of events that begins when a spermatozoon makes contact with a secondary oocyte or its investments, and ends with the intermingling of maternal and paternal chromosomes at metaphase of the first mitotic division of the zygote. The zygote is characteristic of the last phase of fertilization and is identified by the first cleavage spindle. It is a unicellular embryo."9"... the procession of events that begins when a spermatozoon makes contact with a secondary oocyte or its investments, and ends with the intermingling of maternal and paternal chromosomes at metaphase of the first mitotic division of the zygote. The zygote is characteristic of the last phase of fertilization and is identified by the first cleavage spindle. It is a unicellular embryo."9 (Emphasis added.)

The fusion of the sperm (with 23 chromosomes) and the oocyte (with 23 chromosomes) at fertilization results in a live human being, a single-cell human zygote, with 46 chromosomes — the number of chromosomes characteristic of an individual member of the human species. Quoting Moore:

"Zygote: This cell results from the union of an oocyte and a sperm. A zygote is the beginning of a new human being (i.e., an embryo). The expression fertilized ovum refers to a secondary oocyte that is impregnated by a sperm; when fertilization is complete, the oocyte becomes a zygote."10 (Emphasis added.)

This new single-cell human being immediately produces specifically human proteins and enzymes11 (not carrot or frog enzymes and proteins), and genetically directs his/her own growth and development. (In fact, this genetic growth and development has been proven not to be directed by the mother.)12 Finally, this new human being — the single-cell human zygote — is biologically an individual, a living organism — an individual member of the human species. Quoting Larsen:

"... [W]e begin our description of the developing human with the formation and differentiation of the male and female sex cells or gametes, which will unite at fertilization to initiate the embryonic development of a new individual."13 (Emphasis added.)

In sum, a human sperm and a human oocyte are products of gametogenesis — each has only 23 chromosomes. They each have only half of the required number of chromosomes for a human being. They cannot singly develop further into human beings. They produce only "gamete" proteins and enzymes. They do not direct their own growth and development. And they are not individuals, i.e., members of the human species. They are only parts — each one a part of a human being. On the other hand, a human being is the immediate product of fertilization. As such he/she is a single-cell embryonic zygote, an organism with 46 chromosomes, the number required of a member of the human species. This human being immediately produces specifically human proteins and enzymes, directs his/her own further growth and development as human, and is a new, genetically unique, newly existing, live human individual.

After fertilization the single-cell human embryo doesn't become another kind of thing. It simply divides and grows bigger and bigger, developing through several stages as an embryo over an 8-week period. Several of these developmental stages of the growing embryo are given special names, e.g., a morula (about 4 days), a blastocyst (5-7 days), a bilaminar (two layer) embryo (during the second week), and a trilaminar (3-layer) embryo (during the third week).14


Sources:
[1] B. Lewin, Genes III (New York: John Wiley and Sons, 1983), pp. 9-13; A. Emery, Elements of Medical Genetics (New York: Churchill Livingstone, 1983), pp. 19, 93.
[2] William J. Larsen, Human Embryology (New York: Churchill Livingstone, 1997), pp. 4, 8, 11.
[3] Ibid.
[4] Ibid.
[5] Ronan O'Rahilly and Fabiola Mόller, Human Embryology & Teratology (New York: Wiley-Liss, 1994). See also, Bruce M. Carlson, Human Embryology and Developmental Biology (St. Louis, MO: Mosby, 1994), and Keith L. Moore and T.V.N. Persaud, The Developing Human (Philadelphia: W.B. Saunders Company, 1998).
[6] O'Rahilly and Mόller 1994, pp. 13-14.
[7] Ibid., p. 16. See also, Larsen, op. cit., pp. 3-11; Moore and Persaud, op. cit., pp. 18-34; Carlson, op. cit., pp. 3-21.
[8] Note: The number of chromosomes in the definitive oocyte are not halved unless and until it is penetrated by a sperm, which really does not take place before fertilization but is in fact concurrent with and the beginning of the process of fertilization. However, for simplicity's sake, many writers (myself among them) will sometimes assume the reader clearly understands this timing, and simply say, "before fertilization the sperm and the oocyte each contain 23 chromosomes."
[9] O'Rahilly and Mόller, p. 19.
[10] Moore and Persaud, p. 2.
[11] E.g., as determined in extensive numbers of transgenic mice experiments as in Kollias et al., "The human beta-globulin gene contains a downstream developmental specific enhancer," Nucleic Acids Research 15(14) (July, 1987), 5739-47; also similar work by, e.g., R.K. Humphries, A. Schnieke.
[12] Holtzer et al., "Induction-dependent and lineage-dependent models for cell-diversification are mutually exclusive," Progress in Clinical Biological Research 175:3-11 (1985); also similar work by, e.g., F. Mavilio, C. Hart.
[13] Larsen, p. 1; also O'Rahilly and Mόller, p. 20.
[14] Larsen, p. 19, 33, 49.
[1]

My sources:
[1] Irving, Dianne N. "When do human beings begin?"
http://www.vanderbilt.edu/SFL/dnirvi...ing.htm#Embryo

If anyone is tempted to take exception that the facts I use are found on anti-abortion pages, well, try taking facts for your use off of pro-life pages; then we can talk about it.


"Words are deeds." - Wittgenstein

Last edited by Samuel Dravis; 03-10-2006 at 03:45 PM.
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