Stem cell research is among the most promising and controversial technological breakthroughs of our time. What is the halachic perspective on such research and what could the possible objections to such research be?
- In Vitro Fertilization
- Abortion in Jewish Law
- Are Pre-Embryos Included in The Prohibition of Abortion?
- Forty Days
- May a Very Early Embryo be Sacrificed for Stem Cells?
- May We Fertilize Ova Specifically to Create an Embryo to be Sacrificed for Stem Cells?
- "Fences" Around the Law & Use of Stem Cells & Aborted Fetal Tissue
Most cells in the human body are differentiated and, if they maintain the ability to divide at all, have the ability to form only cells similar to themselves. Stem cells have the unique property of being able to divide, while maintaining their totipotent or pluripotent characteristics. Early in mammalian development, stem cells (under the proper conditions) have the ability to differentiate into every cell of the human body (totipotent), potentially forming an entire fetus. Stem cells derived from later stages of mammalian development have the ability to differentiate into multiple cell types, but not into an entire organism. If we were able to manipulate the conditions controlling cellular differentiation, we might be able to create replacement cells and organs, potentially curing illnesses such as diabetes, Alzheimer's disease, and Parkinson's disease.
The ultimate promise of stem cell technology would be to combine it with cloning. Imagine a man dying of liver failure. If we could take a somatic cell from his skin and place the nuclear DNA into a denucleated egg cell, we would have created an almost exact copy of that sick man's cell, capable of differentiating into his clone. Instead of allowing the cloned cell to develop into a fetus, we might place it (or its stem cells alone) into the appropriate environment that would cause it to differentiate into a liver that would be virtually genetically identical to the sick man. If we could "grow" this liver to maturity, we could offer the sick man a liver transplant without the risk of rejection and without the need for anti-rejection drugs.
This sounds like a virtual panacea for many of man's ills. Yet we still do not know if we are able to successfully clone a human, nor are we sure what practical value can be derived from stem cells. We are currently in the realm of fascinating speculation. It will require years of very expensive, labor intensive research to determine the potential that stem cells hold for the treatment, palliation, and cure of human illness. While stem cells have been isolated from adults and aborted fetuses, the best source is the "pre-embryo," the small clump of cells that compose the early zygote only a few days following conception. Therefore, to best investigate the latent possibilities inherent in stem cells, scientists wish to use the approximately 100,000 "excess" frozen pre-embryos that are "left over" from earlier IVF attempts.
There is little argument that the use of stem cells derived from adult somatic tissue pose few ethical problems. The issues raised by stem cell research involve the use of in vitro fertilized eggs which have not yet been implanted in a woman and the use of tissue from aborted fetuses.
The issues raised by stem cell research may be divided into several questions that will be covered in this article.
Artificial insemination has been dealt with a length by a spectrum of poskim (rabbis qualified to decide matters of Jewish law). While artificial insemination by a donor is generally strongly condemned, the use of a husband's sperm for artificial insemination in cases of necessity was accepted by most Rabbinical authorities. The question of in vitro fertilization was dealt with later. A significant majority of authorities accepted in vitro fertilization under the same rubric and limitations as artificial insemination, including the fulfillment of the mitzvah of procreation. However, a fundamentally new question arose. What is the status of the "spare" embryos that are not implanted as part of the first cycle of IVF? Must they be implanted in the mother as part of another attempt at pregnancy. May/must they be donated to another women to allow the pre-embryo its chance at life? May they remain frozen indefinitely? Most importantly to our topic, the question arose - may pre-embryos be destroyed? To answer this question, we must first generally examine the Jewish approach to abortion.
The traditional Jewish view of abortion does not fit conveniently into either of the major "camps" in the current American abortion debate. We neither ban abortion completely, nor do we allow indiscriminate abortion "on demand." To gain a clear understanding of when abortion is sanctioned, or even required, and when it is forbidden, requires an appreciation of certain nuances of halakhah (Jewish law) which govern the status of the fetus.
The easiest way to conceptualize a fetus in halakhah is to imagine it as a full-fledged human being - but not quite. In most circumstances, the fetus is treated like any other "person." Generally, one may not deliberately harm a fetus, and sanctions are placed upon those who purposefully cause a woman to miscarry. However, when its life comes into direct conflict with an already born person, the autonomous person's life takes precedence.
It follows from this simple approach that, as a general rule, abortion in Judaism is permitted only if there is a direct threat to the life of the mother by carrying the fetus to term or through the act of childbirth. In such a circumstance, the baby is considered tantamount to a rodef, a pursuer after the mother with the intent to kill her. Nevertheless, as explained in the Mishna (Oholos 7:6), if it would be possible to save the mother by maiming the fetus, such as by amputating a limb, abortion would be forbidden. Despite the classification of the fetus as a pursuer, once the baby's head has been delivered, the baby's life is considered equal to the mother's, and we may not choose one life over another, because it is considered as though they are each pursuing the other.
Judaism recognizes psychiatric as well as physical factors in evaluating the potential threat that the fetus poses to the mother. However, the danger posed by the fetus (whether physical or emotional) must be both probable and substantial to justify abortion. The degree of mental illness which must be present to justify termination of a pregnancy is not well established and therefore criteria for permitting abortion in such instances remain controversial.
As a rule, halakhah does not assign relative values to different lives. Therefore, almost all major poskim forbid abortion in cases of abnormalities or deformities found in a fetus. Rabbi Moshe Feinstein, one the greatest poskim in this century, rules that even amniocentesis is forbidden if it is performed only to evaluate for birth defects for which the parents might request an abortion. Nevertheless, a test may be performed if a permitted action may result, such as performance of amniocentesis or drawing alpha-fetoprotein levels for improved peripartum or postpartum medical management. While most poskim forbid abortion for "defective" fetuses, Rabbi Eliezar Waldenberg (in his "Tzitz Eliezer," vol. 9, chapter 51:3) is a notable exception. Rabbi Waldenberg allows first trimester abortion of a fetus which would be born with a deformity that would cause it to suffer, and termination of a fetus with a lethal fetal defect such as Tay Sachs up to the end of the second trimester of gestation.
The question of abortion in cases of rape, incest, and adultery is a complex one, with various legal justifications propounded on both sides. In cases of rape and incest, a key issue would be the emotional toll exacted from the mother in carrying the fetus to term. The same analysis used in other cases of emotional harm might be applied here. Cases of adultery interject additional considerations into the debate which are beyond the scope of this short article.
In sum, the parameters determining the permissibility of abortion within halakhah are subtle and complex.
While the practical aspects of the Jewish approach to abortion are relatively agreed upon, the exact source and nature of the prohibition is not. Depending on the origin of the prohibition, the application to the pre-embryo will differ. For instance, while most halachic authorities consider the prohibition of abortion to be from the Torah, a few consider it to be Rabbinic in nature. It is interesting to note that both the person who performs the abortion as well as the woman who voluntarily allows it to be done are culpable.
The most obvious place to look for the Biblical prohibition would be from the aseret ha'dibrot (Ten Commandments), "Thou shalt not murder". This prohibition, called retzicha, usually carries a death penalty for transgression. Nevertheless, it appears the Torah itself teaches that killing a fetus is not equivalent to killing an adult. The Torah specifically states that if in the course of an altercation with a third party, a person causes a woman to miscarry, he pays only monetary damages, while if the woman herself were to die of her injuries, the aggressor would receive a death sentence. Rabbi Yehuda Ashkenazi, in his commentary on the Code of Jewish Law, reasons from here that a fetus is not a full-fledged person, since regarding the one who hits the woman, causing her to miscarry, ". . . he pays the value of the child and we do not label him a murderer, nor do we execute him. . .."
Notwithstanding the statement of Rabbi Ashkenazi, several poskim rule that abortion does represent murder, but without the punishment of death. This law is similar to the law of one who kills a treife (a specific type of terminally ill person), for whom there is a prohibition of murder, but no death penalty. If the pre-embryo is included in this prohibition, then very little short of the pre-embryo posing a threat to someone's life could justify its destruction. An independent threat to the life of a third party would not suffice to allow destroying the pre-embryo.
The argument regarding whether a fetus is included in the prohibition of murder is complicated and fascinating. Both positions garner support from two sides of the same page of the Talmud. Arachin 7a states that the court should strike the abdomen of a pregnant woman to cause a miscarriage prior to her execution. The life of the fetus seems inconsequential in that discussion. On the other hand, Arachin 7b states that the Sabbath may be desecrated for the life of a fetus, something which may only be done to save a life, for pikuach nefesh. This apparent contradiction is dealt with at length in the responsic literature.
But is the pre-embryo included in this prohibition? That question is best answered by evaluating the next possible Biblical source for abortion. When Noah and his family exited the ark, G-d commanded them seven laws, which apply to all of humanity. The usual translation of one of these laws is: "Whoever sheds the blood of man, by man shall his blood be shed." The Torah clearly demands capital punishment for murder. While this prohibition appears straightforward, there is a fascinating twist.
The Talmud attempts to prove that non-Jews, who are not obligated by most of the Torah's commandments given at Mount Sinai, are forbidden to perform abortions. The Talmud brings the literal translation of the previously mentioned passage (with slightly altered punctuation), which is: "Whoever sheds the blood of man, within man, his blood shall be shed." It then asks: "What is the meaning of 'man within man'? This can be said to refer to a fetus in its mother's womb." This prohibition, as part of the Noachide laws, would apply to all people, Jew and non-Jew alike, although for technical reasons, the degree of severity would differ.
Once the "standard" prohibition of retzicha (murder) is separated from that of killing a fetus, we may investigate how this difference might affect the status of the pre-embryo. From the Talmudic discussion of abortion, we might expect that pre-embryos are not covered by the prohibition of abortion, because they have never been implanted. The rationale for such a decision is based on the concept that a pre-embryo left in its petri dish will die. It is not even potential life until it is implanted in an environment in which it can mature.
Others derive the prohibition of abortion from the Torah's proscription of inflicting damage to one's self or others (chavala). One may not wound one's self without a valid reason (such a medical necessity as in surgery). Obviously, one may not damage someone else. As a result, some claim that the prohibition of abortion arises from the prohibition of the woman wounding herself, while others feel that the derivation is from the prohibition of wounding the fetus. Unlike murder, for which only a threat to the mother's life could justify killing the fetus, the rationale of chavala allows greater leeway in allowing its abrogation. Particularly, if the wounding of the mother is the prohibition, her consent to being wounded might be considered a determining factor. Whether this prohibition applies to a pre-embryo is open to debate (albeit my personal opinion is that the prohibition of chavala does not apply at this level).
The last possible prohibition to consider is the Torah's forbidding of "wasting seed" (hashchatat zera). This is the main prohibition involved in questions of male contraception (for example, condoms) as well as the laws governing gathering of sperm for analysis, IVF, or artificial insemination. The prohibition forbids the "useless" emission or destruction of sperm that could create life. Some halachic authorities have ruled that excess sperm from fertility treatments may be destroyed. Further, the emission of semen for analysis has been permitted as part of the process of procreation in those suffering from infertility. (Nevertheless, according to most poskim, this prohibition does not apply once fertilization has occurred.) Since this ban may be waived for the sake of saving a life, it is conceivable that destroying a pre-embryo to save someone's life (or potentially treat severe illness; this would bring us into the complicated question of "v'chi omrim lo l'adam chatei bishvil sheyizke chaveirecha" -- do we allow one to sin in order to save his friend, -- an issue beyond the scope of this article) would be permitted as part of the mitzvah of pikuach nefesh.
Two positive Biblical commandments bear on the obligation to save life (the obligation of hatzala). The Torah requires that we "Do not stand idly by as your neighbor's blood is being shed." This mitzvah is interpreted by the Talmud to require one to expend positive effort and even money to protect an endangered person. Maimonides learns the whole commandment for a qualified individual to heal his neighbor from the obligation to return lost objects. Regarding a lost object, the Torah commands: ". . . and you should surely restore it to him." From an extra letter in the sentence, Maimonides derives that if one must return a lost object, he must certainly return someone's "lost" health.
Both of these positive commandments may apply regardless of whether there may be any prohibition of abortion for a pre-embryo. But do these positive commandments apply to a pre-embryo? That is, do we have a positive obligation to protect the pre-embryo that is sitting in the freezer?
In our analysis, we must also evaluate whether we are more lenient with the destruction of an embryo prior to forty days gestation. There is reason to argue that prior to forty days gestation, the fetus lacks "humanity." The Mishna states that a miscarriage prior to forty days does not cause tumat leida. The daughter of a Cohen (priest) whose non-Cohen husband has died may continue eating trumah (tithes) only if she has no children and is not pregnant. Rav Chisda states that in a case where her non-Cohen husband died soon after marriage, she may continue eating trumah for forty days. He reasons that if she is not pregnant, then there is no problem, and that if she is pregnant, that up to forty days the fetus is "mayim b'alma (mere water)."
These sources suggest that a fetus prior to forty days gestation is not considered to be an actual person and we might extrapolate that destruction of such a fetus is not forbidden by Jewish law. If we now apply this reasoning to the possible sources for abortion discussed above, we note consistency on the part of the poskim.
Rabbi Unterman, former Ashkenazi chief Rabbi of Israel, who ruled that a fetus is protected by the prohibition of murder (retzicha), rejects these sources as removing the early embryo from the prohibition of murder. He bolsters his opinion by quoting from Toras Ha'Adam, a famous Jewish law book by Nachmanides (Ramban) that discusses medical issues. The Ramban quotes the Ba'al Halachot Gedolot, who asserts that one may desecrate the Sabbath for a fetus because, by desecrating one Sabbath, the fetus will be able to fulfill many Sabbaths in the future. Thus, the Ba'al Halachot Gedolot argues that saving the life a fetus before forty days overrides the Sabbath; therefore, argues Rabbi Unterman, feticide is murder.
Rabbi Yair Bachrach, author of Chavot Yair, does not accept the forty days distinction because he derives the prohibition of feticide from wasting male seed, which is prohibited even before conception.
Rabbi Yosef Trani (author of Responsa Maharit), who argues that abortion is forbidden as chavala (wounding) of the mother, does not specifically mention the forty day cutoff. However, Rabbi Yechiel Weinberg (author of the Responsa Seridei Aish), clearly held that there is no prohibition of abortion before forty days according to Rabbi Trani's opinion since there is no "limb" to injure prior to formation of a recognizable fetus at forty days. Rabbi Weinberg himself at first permitted abortion prior to forty days, but later reconsidered his position.
All of the above approaches apply only to Jews who are bound by Torah law. The prohibition of abortion for non-Jews, as discussed above, devolves from the Noachide laws. Of course, non-Jews are forbidden to commit homicide. Yet, according to many commentators, non-Jews are not bound by the commandment in Leviticus 19:16 to protect the lives of their comrades, since it was not commanded to Noah. The scope of their prohibition includes murder and "shedding blood of man within man." These obligations include only actual lives, not potential lives. Therefore, according to Rabbi Unterman, there is no prohibition of abortion for a non-Jew, nor for a Jew to aid in such an abortion, before the fortieth day of gestation.
Now that we have analyzed the possible ethical issues in destroying pre-embryos, what is the final outcome? For non-Jews, the issue appears most direct. The combination of the pre-embryo never having existed within a uterus and the generally accepted leniency toward abortion within the first forty days, would strongly argue for a permissive ruling regarding the destruction of pre-embryos for stem cells.
Regarding Jews, the answer is more complicated. Since stem cell research is a new endeavor and cloning of humans has not yet occurred, there are no published responsa on the topic. We must, therefore, look to more practical cases that encompass our question to find an applicable ruling. We find such an issue with respect to the best course of action for couples who wish to avoid having children with Tay Sachs disease when both partners are carriers of the Tay Sachs gene. A similar problem arises in families where the wife carries a gene for a sex-linked disease, such as Fragile-X.
The most promising option for such couples is preimplantation diagnosis, in which a zygote conceived in vitro has a few cells removed to be tested for genetic defects before implantation. Only a zygote that is not homozygous for Tay Sachs or not a male carrier of Fragile-X would be implanted. Rabbi Yosef Shalom Eliyashuv, possibly the most influention posek in Israel today, has permitted preimplantation diagnosis and destruction of affected zygotes to prevent cases of Fragile-X and even in a case of a woman with neurofibromatosis who only had skin lesions. Rabbi Dovid Feinstein has taken a similar view as to the permissibility of discarding "extra" pre-embryos. Pre-implantation diagnosis, which is already accepted by some Rabbinic authorities, is likely to be acceptable to most Jewish legal experts when used to prevent serious diseases in offspring.
Based on these rulings, it would seem that we now have a practical answer to our question of stem cell research. If the pre-embryo may be destroyed, it certainly may be used for research purpose and other life-saving work. In fact, Rabbi Moshe Dovid Tendler, in testimony for the National Bioethics Advisory Commission, argued strongly in favor of the use of pre-embryos for stem cell research. Nevertheless, it is important to realize that this conclusion is not unanimous and that all of these rulings are predicated upon the understanding that the pre-embryo is not included in the prohibition of retzicha (murder).
The creation of embryos for the purpose of taking their stem cells is a complex issue. While no responsa yet exist specifically dealing with this question, it is likely that Rabbinic authorities will not favor such a leniency. The mere existence of already created pre-embryos creates a need to decide the halachic ramifications of their destruction. We therefore may decide that such research is permitted bedieved (ex post facto), once the pre-embryos exist. However, since there are poskim who forbid abortion even within the first forty days, it is much harder to argue lichatchila (a priori) that creation of pre-embryos with the intention of destroying them is permitted.
There are additional questions that we as a society must ponder. May we and should we deliberately create pre-embryos in order to destroy them?
The Rabbis often create protective edicts (gezerot) to prevent the desecration of Torah law. Additionally, the Rabbis may promulgate decrees intended to protect Torah values by preventing untoward behavior that is not already prohibited by the Torah itself. For example, more than 1000 years ago, Rabbenu Gershon enacted gezerot banning polygamy and opening the mail of others, despite the absence of actual Torah prohibitions for either of these two actions.
The protection of life is a strongly held Torah ideal. While the destruction of pre-embryos in the course of fertility treatments or to prevent disease may be permitted, this does not mean that pre-embryos may be destroyed without compunction. To avoid the proverbial "slippery slope," should we ban stem cell research on embryonic stem cells as a dangerous encroachment on the sanctity of life? That is, even if pre-embryos may be destroyed, should we enact preventative laws barring stem cell research that requires the destruction of potential lives to avoid cheapening life by treating the process of creating humans as another scientific process, stripped of its miraculous underpinnings? In his testimony, Rabbi Tendler summed up the issue of protective enactments as follows:
Jewish law consists of biblical and rabbinic legislation. A good deal of rabbinic law consists of erecting fences to protect biblical law. Surely our tradition respects the effort of the Vatican and fundamentalist Christian faiths to erect fences that will protect the biblical prohibition against abortion. But a fence that prevents the cure of fatal diseases must not be erected, for then the loss is greater than the benefit. In the Judeo-biblical legislative tradition, a fence that causes pain and suffering is dismantled. Even biblical law is superseded by the duty to save lives, except for the three cardinal sins of adultery, idolatry, and murder. . . Life saving abortion is a categorical imperative in Jewish biblical law. Mastery of nature for the benefit of those suffering from vital organ failure is an obligation. Human embryonic stem cell research holds that promise. . ..
Human embryonic germ cells may also be derived from gamete ridge tissue removed from first trimester abortuses (at approximately eight-weeks gestation). While abortion of fetuses is a grave offense, it is difficult to justify prohibiting the use of life-saving tissue from these aborted fetuses for fear of encouraging or condoning abortion. This is another case where the cost of a preventative enactment might be the avoidable death of human beings. 
Sources: Dr. Eisenberg resides with his wife and children in Bala Cynwyd, Pa. This article was reviewed for halachic accuracy by Rabbi Sholom Kaminetsky of the Talmudical Yeshiva of Philadelphia. If you have any comments or questions about this article or other medical / halachic issues, feel free to contact Dr. Eisenberg at [email protected].
 While the nuclear DNA would be identical to the donor skin cell, the mitochondrial DNA would be that of the donor egg.
[2K] See "Artificial Insemination in Jewish Law," Maimonides: Health in the Jewish World, Vol 5, No. 1, Winter, 1999.
 With the important exceptions of (1) Rabbi Ovadia Yosef, who forbids it and rules that it does not fulfill the obligation of fathering children, (2) Tzitz Eliezer XV, no. 45, and (3) Rabbi Moshe Sternbach who denies paternity to the sperm donor and forbids the procedure.
 The use of sperm for IVF once the mitzvah of procreation has been fulfilled is more controversial.
 See the article by Rabbi Yitzchok Breitowitz, "The Preembryo in Halacha" posted on JLaw.com at http://www.JLaw.com/Articles/preemb.html
 The development of cryogenic techniques to freeze pre-embryos only pushed off the crucial question of whether pre-embryos could be destroyed. Prior to cryogenic techniques, several Rabbinic authorities ruled that all fertilized embryos must be implanted. This severely limited the availability of IVF to Torah observant Jews because of the great expense and low yields of each IVF attempt (necessitating fertilization of many ova), and the inherent risk of implanting many embryos. With the advent of cryogenic techniques, many ova could be fertilized with only a few implanted. Nevertheless, the question of disposition of these "frozen" pre-embryos which now number approximately 100,000 remains.
 Nishmat Avraham, Orach Chaim 656:1 (p. 92)
 Exodus 20:13
 Exodus 21:22-23
 Be'er Hetiv, Choshen Mishpat 425:2
 See Rabbi I.Y. Unterman, Responsa Shevet M'Yehuda, Vol. I, p. 29 and Noam 6 (1963): 1-11.
 A treife is a person with an organic illness that is expected to be fatal within a year.
 See Igrot Moshe, Choshen Mishpat II, 69B
 For more extensive treatment of this debate, see Jewish Ethics and Halakhah For Our Time, Sources and Commentary, Vol. I, by Rabbi Basil F. Herring.
 To spare her the embarrassment of bleeding during her execution.
 Genesis 9:6
 Sanhedrin 67b: "In the name of Rabbi Yishmael they said: A ben Noach [is liable] even for killing a fetus. What is the reasoning of Rabbi Yishmael? Because it is written [in Genesis 9:6]: 'Whoever sheds the blood of man by man [literally "in man"], his blood shall be shed'. What is the meaning of 'man in man'? This can be said to refer to a fetus in its mother's womb."
 Since the Torah was given to the Jews at Mount Sinai, only they are bound by its commands. Nevertheless, all laws given to Noah, the father of all nations, are binding on non-Jews.
 Tosofot, Chullin 33a, (d.h. "Echad oveid kochavim"), Tosofot, Sanhedrin 59a (d.h. "Layka")
 Bava Kamma 90b based on Genesis 9:5 ("the blood of your lives I will surely require"). See Responsa Maharit 97 & 99. See also Responsa Seridei Aish, vol. 3, no. 127 (originally published in Noam 9: 193-215).
 The laws of damage in halakhah are extensively discussed in the Torah, Talmud, and codes of Jewish law.
 See Responsa Seridei Aish, vol. 3, no. 127 (p. 249)
 Rabbi J. David Bleich, Contemporary Halakhic Problems, Vol. 1, p. 341
 As noted above, the fetus would be classified a rodef
 See Nida 13b and Responsa Chavot Yair, no. 31. Responsa Sheilot Yaavetz, no. 43 argues that once the sperm has been deposited in the woman, the primary prohibition of hashchatas zera no longer applies.
 Igrot Moshe Even HaEzer I:70, III:14
 Generally, all Torah prohibitions except for murder, idolatry, and forbidden sexual relationships are waived to save a human life.
 Leviticus 19:16
 Sanhedrin 73a
 Deuteronomy 22:1-2
 Maimonides, Commentary on the Mishnah, Nedarim 4:4
 Nidda 30a
 Tumat leida is the impurity that is created by the birth process, whether live or by miscarriage.
 Yevamot 69b
 Torat HaAdam (in Mosad HaRav Kook Kitvei Haramban, Vol. 2, p. 29)
 This line of reasoning is brought in Talmud Yoma 85b as one possible reason for why saving a life overrides the Sabbath.
 See Responsa Sheilot Yaavetz, no. 43, where Rabbi Yaakov Emden argues that "wasting seed" only bars preventing the semen from reaching the woman's uterus. He nevertheless forbids abortion prior to forty days for other reasons.
 Seridei Aish, vol. 3:350, n.7
 Seridei Aish, vol. 3, no. 127 (p. 249)
 Responsa Shevet M'Yehuda, Vol. I, 9 and Noam 6:4.
 Rabbi Chaim Ozer Grodzinski (Responsa Achiezer, III, 65:14) even entertains the possibility that there may be no Biblical prohibition of abortion before forty days. See also: Tzofnat Paneach 59; Responsa Bet Shlomah, Choshen Mishpat 162; Torat Chesed, Even Ha'ezer, 42:33 all of whom discuss the decreased stringency of abortion within the first forty days.
 Males with a single gene for a sex-linked disease will be affected by the disease.
 Personal correspondance with Dr. Avraham Steinberg.
 Personal correspondance with Rabbi Sholom Kamenetsky.
 Stem Cell Research and Therapy: A Judeo-Biblical Perspective, Ethical Issues in Human Stem Cell Research, Volume III: Religious Perspectives, September 1999, pp.H-3 to H-5. The full text may be downloaded from the National Bioethics Advisory Commission website at http://bioethics.gov/pubs.html.
 "The Judeo-biblical tradition does not grant moral status to an embryo before forty days of gestation. Such an embryo has the same moral status as male and female gametes, and its destruction prior to implantation is of the same moral import as the 'wasting of human seed.' After forty days-the time of 'quickening' recognized in common law-the implanted embryo is considered to have humanhood, and its destruction is considered an act of homicide. Thus, there are two prerequisites for the moral status of the embryo as a human being: implantation and forty days of gestational development. The proposition that humanhood begins at zygote formation, even in vitro, is without basis in biblical moral theology." Testimony of Rabbi Moshe Dovid Tendler, Ph.D , Stem Cell Research and Therapy: A Judeo-Biblical Perspective, Ethical Issues in Human Stem Cell Research, Volume III: Religious Perspectives, September 1999, p.H-3.
 E.g., Rabbi J. David Bleich has voiced opposition to the destruction of pre-embryos and their use in stem cell research.
 Responsa Seridei Aish, vol. 3:350, n.7, Responsa Shevet M'Yehuda, 1;50, Responsa Maharash Engel, 7:85, and Rabbi Moshe Yonah Zweig, Noam 7:48.
 "In stem cell research and therapy, the moral obligation to save human life, the paramount ethical principle in biblical law, supersedes any concern for lowering the barrier to abortion by making the sin less heinous. Likewise, the expressed concern that this research facilitates human cloning is without merit. First, no reputable research facility is interested in cloning a human, which is not even a distant goal, despite the pluripotency of stem cells. Second, those on the leading edge of stem cell research know that the greater contribution to human welfare will come from replacement of damaged cells and organs by fresh stem cell products, not from cloning. Financial reward and acclaim from the scientific community will come from such therapeutic successes, not from cloning." Testimony of Rabbi Moshe Dovid Tendler, Ph.D., Stem Cell Research and Therapy: A Judeo-Biblical Perspective Ethical Issues in Human Stem Cell Research, Volume III: Religious Perspectives, September 1999, p.H-4.
 Other issues applicable to stem cell research are generic and apply equally to all research. Full informed consent, careful risk-benefit analysis, allocation of scarce resources, and the role of financial gain and renumeration in research have all been dealt with in Jewish law, and are beyond the scope of this article.