Human Genetics

1. Human Genetics Concepts and Applications Eighth Edition Powerpoint Lecture Outline Ricki Lewis Prepared by Dubear Kroening University of Wisconsin-Fox Valley

2. Chapter 21 Reproductive Technologies

3. Advancing Technology Raises Ethical Dilemmas Examples • Post mortem sperm retrieval • With and without donor consent • Sperm and ooctyte banking • Cancer patients • Military personnel • Genetic testing of embryos prior to implantation • To identify lethal conditions • To provide a suitable umbilical stem cell donor

4. Assisted Reproductive Technologies • Methods that replace the source of a male or female gamete, aid fertilization or pregnancy • Developed to treat infertility but are becoming part of genetic screening Examples • Surrogate pregnancy • In vitro fertilization • Sperm or egg donor

5. Infertility and Subfertility • Infertility is the inability to conceive a child after a year of frequent intercourse without contraceptives • Subfertility distinguishes couples who can conceive, but require longer time than usual • A physical cause can be identified in 90% of cases: 30% in males, 60% in females

6. Causes of Subfertility and Infertility Table 21.1

7. Male Infertility • One in 25 men are infertile • Easier to detect, but often harder to treat • Most cases of male infertility are genetic • Due to small deletions of the Y chromosome that remove genes important for spermatogenesis • Mutations in genes for androgen receptors or other hormones promoting sperm development • In cases of low sperm count, sperm can be stored frozen, then pooled • Lack of motility in sperm prevents movement in the female reproductive tract

8. Sperm Shape and Motility are Important Figure 21.2

9. Sites of Reproductive Problemsin Women Figure 21.3

10. Female Infertility • Pregnancy of healthy women under 30 usually occurs within 3-4 months. • Irregular menstrual cycles can make it difficult to localize problems. • Tracking ovulation cycles aids determination of the most likely days for conception. • Fertility drugs stimulate ovulation but may induce release of multiple oocytes. • Blocked fallopian tubes can result in ectopic pregnancy (tubal pregnancy). • Excess tissue growth in uterine lining • Fibroids: benign tumors • Endometriosis: buildup of uterine lining

11. Assisted Reproductive Technologies ART • 1% of births in U.S. each year (4 million total) from ART, 0.4% single and 16% multiple • Examples • Intrauterine insemination • Surrogate motherhood • In vitro fertilization (IVF) • Gamete intrafallopian transfer (GIFT) • Zygote intrafallopian transfer (ZIFT) • Oocyte banking and donation • Preimplantation genetic diagnosis

12. Table 21.2

13. Intrauterine Insemination • Donated sperm in a woman’s reproductive tract, typically at the cervix or in uterus • 1790, first reported pregnancy from artificial insemination • 1953, methods for freezing and storing sperm were developed • Sperm catalogs list personal characteristics

14. Surrogate Motherhood • In surrogate motherhood, a woman carries a pregnancy to term for another woman who cannot conceive and/or carry the pregnancy • Custody rights are given up at birth • A surrogate mother may or may not have contributed an oocyte • Complex legal and emotional issues must be considered

15. In vitro Fertilization (IVF) • For in vitro fertilization or IVF, a sperm fertilizes an oocyte in a culture dish • Embryos are transferred to the oocyte donor’s uterus (or a surrogate’s uterus) for implantation • 1978, first IVF child born • Intracytoplasmic sperm injection (ICSI) is more effective than IVF alone

16. Intracytoplasmic Sperm Injection • For cases in which sperm cannot penetrate the oocyte, IVF can be accompanied by ICSI which injects sperm directly into the oocyte • ICSI allows conception in cases of low sperm count, abnormal sperm shape, sperm motility problems Figure 21.4

17. Methods for Improving IVF • Transfer embryos at blastocyst stage • Culture fertilized ova and early embryos with cells that normally surround the oocyte, so they can provide growth factors • Screen early embryos for chromosome abnormalities and implant only those with normal karyotypes

18. Gamete Intrafallopian Transfer (GIFT) • GIFT is a method in which superovulated oocyte from a woman and sperm from her partner are placed together in her uterine (fallopian) tube • Fertilization occurs in the woman’s body • Allows conception in cases of fallopian tube blockage • 27% success rate

19. Zygote Intrafallopian Tube Transfer (ZIFT) • IVF ovum is introduced into the uterine tube and allowed to move to the uterus for implantation • GIFT and ZIFT are done much less frequently than IVF • Will not work for women with scarred uterine tubes • 29% successful

20. Oocyte Banking and Donation • Oocytes, like, sperm can be stored frozen, only 3% successful • New technique can freeze strips of ovarian tissue • Difficulties because oocytes pause in meiosis II until fertilization occurs • Women can store their own oocytes to have children later or prior to undergoing chemotherapy • Donated oocytes can be used by women with infertility problems, 20-50% successful • Embyro adoption

21. Preimplantation Genetic Diagnosis • The technique of preimplantation genetic diagnosis (PGD) allows detection of genetic abnormalities prior to implantation • One cell or blastomere of an 8-celled embryo can be removed for testing. The remaining cells will complete normal development • 1992 first child born following PGD to screen for cystic fibrosis alleles present in her family • PGD can be combined with IVF for women who have had multiple miscarriages • Polar body biopies

22. Preimplantation Genetic Diagnosis Figure 21.5

23. Table 21.3

24. ART Disasters Can Occur • Technology can create opportunities for extremely complex “families” • Multiple legal and ethical questions must be addressed • Examples of ART disasters in Table 21.4 Table 21.4

25. Figure 21.6