Miscellaneous+Reproductive+Topics+MV

Molly Vaughn 5 November 2008 Human Biology

Miscellaneous Reproduction Topics

(1) What does IVF stand for? What does it treat? How does the doctor get the eggs? Where are the embryo’s made and when are they implanted? Where are they implanted? (p.334) - IVF stands for In Vitro Fertilization. During IVF, conception occurs in laboratory glassware. Ultrasound machines can now spot follicles in the ovaries that hold immature eggs; therefore, the latest method is to forgo the administration of fertility drugs and retrieve immature eggs by using a needle. The immature eggs are then brought to maturity in glassware, and then concentrated sperm are added. After about two to four days, the embryos are ready to be transferred to the uterus of the woman, who is now in the secretory phase of her uterine cycle. If desired, the embryos can be tested for genetic disease, and only those found to be free of disease will be used. If implantation is successful, development is normal and continues to term.

(2) Embryos that are not implanted are frozen? What can happen to frozen embryos? (p.335) - In spite of potential trials, thousands of people undergo fertility treatment every year. Its popularity has brought a number of ethnical issues to light. For example, the estimated high numbers stored frozen embryos (a few hundred thousand in the United States) has generated debate about their fate, complicated by the fact that the long-term viability of frozen embryos is not well understood. Scientists may worry that embryos donated to other couples are ones that were already screened out from one implantation, and not likely to survive. Some religious groups strongly oppose destruction of these embryos or their use in research. Patients for whom the embryos were created generally feel that they should have sole rights to make decisions about their fate. However, a fertility clinic may no longer be receiving monetary compensation for the storage of frozen embryos and unable to contact the couples for whom they were produced. The question then becomes whether the clinic now has the right to determine their fate.

(3) What is an ectopic pregnancy? (p. 357) - Implantation of the embryo in a location other than the uterus, most often in an oviduct.

(4) Briefly describe how cloning is done. (p. 362) - A donor 2n nucleus is substituted for the n nucleus of an egg; a stimulus is applied that triggers cell division, and the resulting embryo is implanted into a surrogate mother where it develops to term.

(5) What are some the problems that have developed in cloned animals? (p. 362) - 1) The vast majority of pregnancies involving clones are not successful. To clone Dolly the sheep, it took 247 tries before one was successful. In many cases, the clone grows abnormally large, and the uterus enlarges with fluid to the point it can rip apart. Almost all clone pregnancies spontaneously abort. 2) Of the small number of animal clones born, most have severe abnormalities: malfunctioning livers, abnormal blood vessels and heart problems, underdeveloped lungs, diabetes, immune system deficiencies are all seen in newborns. Several cow clones had head deformities-none survived very long. 3) Even if the newborn clone appears healthy, it usually soon develops diseases seen in older animals. Dolly was euthanized in 2003 because she was suffering from lung cancer and crippling arthritis. She had lived only half the normal life span for a Dorset sheep.

(6) What is the difference between reproductive cloning and therapeutic cloning? What are the pros and cons of each. (p. 362) - Reproductive cloning is quite different from therapeutic cloning. In reproductive cloning, the desired end is an individual. In therapeutic cloning, the desired end is not an individual; rather, it is the embryonic cells that possibly can be “coaxed” into becoming various cell types. The purpose of therapeutic cloning is (1) to learn more about how specialization of cells occurs and (2) to provide cells and tissues that could be used to treat human illnesses, such as diabetes, spinal cord injuries, Parkinson disease, and so forth. In the United States, investigators can use only embryonic stem cell lines that already exist and cannot start new ones because of ethical concerns. However, researchers can freely make use of adult stem cells that reside in most tissues of the body. Investigators have been able to isolate adult’s stem cells and use them to regenerate nerve tissue for the treatment of Parkinson disease, for example.

(7) When can you tell if an embryo is a boy or girl? (p. 364) - You can tell if an embryo is a boy or a girl at about the 14th week of pregnancy when the embryo starts to grow external genitals.

(8) Describe two causes of cases where a person is XY (male) but looks and acts female. (p. 365) - It’s not correct to say that all XY individuals develop into males. Some XY individuals become females (XY female syndrome). Similarly, some XX individuals develop into males (XX male syndrome). In individuals with the XY female syndrome, a piece of the Y chromosome is missing. In individuals with the XX male syndrome, this same small piece is present on an X chromosome. The piece of a Y chromosome that causes male genitals to develop is called the SRY (sex determining region of the Y) gene. The SRY gene causes testes to form, and then the testes secrete these hormones: (1) Testosterone stimulates development of the epididymides, vasa deferentia, seminal vesicles, and ejaculatory duct. (2) Anti-Mullerian hormone prevents further development of female structures, and instead causes them to degenerate. (3) Dihydrotestosterone, which is derived from testosterone, directs the development of the urethra, prostate gland, penis, and scrotum.

(9) What is true hermaphroditism? (p. 365) - True gonadal hermaphroditism in which a person has both ovarian and testicular tissue is rare. However, it is estimated that about 1% of the population may have male pseudohermaphroditism. The individual has testes but appears to be a normal female until puberty. The testes never produce testosterone or dihydrotestosterone. Anti-Mullerian hormone is produced and the female set of tubes degenerate. At puberty, the clitoris begins to enlarge as a response to testosterone produced by the adrenal cortex. The clitoris even looks like a penis; the voice deepens, and muscles enlarge. There is no breast development, and the individual does not menstruate. In the Dominican Republic, this syndrome is called guevedoces, which means “penis at age 12.”

(10) What is stage 3 of birth? What happens? (p. 369) - The placenta, or afterbirth, is delivered during the third stage of parturition. About 15 minutes after delivery of the baby, uterine muscular contractions shrink the uterus and dislodge the placenta. The placenta then is expelled into the vagina. As soon as the placenta and its membranes are delivered, the third stage of parturition is complete.