Human Genetics: Concepts and Applications (Lewis), 9th Edition

Chapter 21: Reproductive Technologies

Chapter Outline

CHAPTER OVERVIEW

1. Assisted reproductive technologies (ARTs) provide several ways for people to have children who might not otherwise be able to do so.
2. Countries vary in the extent of their regulation of ARTs.

1. Infertility is the inability to conceive a child after one year of trying.
2. The cause of infertility can be determined about 90% of the time. The male contributes about 30% of the time, the female 60%, or both partners may be involved.
3. Subfertility is used to describe couples that can conceive unaided, but require a longer time to succeed.

1. Male infertility may be due to low sperm count, sperm that are immobile or abnormal in structure.
2. Around one third of the cases of male infertility involve deletions of genes involved in spermatogenesis located on the Y chromosome.
3. Infertility affects about 4% of men.

1. Female infertility can be due to an irregular menstrual cycle or blocked fallopian tubes.
2. Fibroid tumors, endometriosis, or a misshapen uterus may prevent implantation of a fertilized ovum, and secretions in the vagina and cervix may inactivate or immobilize sperm.
3. Oocytes may fail to release a sperm-attracting biochemical.
4. Early pregnancy losses due to abnormal chromosome number may be mistaken for infertility; this is more common among older women.

1. Medical tests to identify the cause of infertility are conducted on the male first.
2. Sperm are checked for number, motility, and morphology.
3. Genetic analysis of the Y chromosome may reveal deletions.
4. If the male is fertile, a gynecologist will examine the structures of the woman's reproductive system and conduct tests to assess female infertility.

1. In artificial insemination, donor sperm are placed into a woman's reproductive tract.
2. X-bearing and Y-bearing sperm can be enriched to enhance sex selection.

1. A genetic and gestational surrogate mother is artificially inseminated with sperm and provides her uterus for nine months.
2. A gestational surrogate carries a fetus conceived in vitro with gametes from the genetic parents.

1. In IVF, a sperm and an oocyte meet in a laboratory dish and an early embryo is then transferred to the uterus.
2. Intracytoplasmic sperm injection (ICSI) can enable immobile sperm to fertilize an oocyte.
3. Preimplantation embryos can be frozen for later use.

1. In GIFT, sperm and oocytes are placed together in a fallopian tube past a blockage.
2. In ZIFT, a preimplantation embryo conceived in vitro is placed in a fallopian tube.

1. The oocytes used for IVF can be donated.
2. Embryo adoption involves an oocyte donor who is artificially inseminated.
3. The donor then has a preimplantation embryo washed out of her uterus and transferred to the gestational mother.
4. Cytoplasmic donation is a technology that is used to rejuvenate the oocytes of older women with the injected cytoplasm of oocytes from a younger woman.

1. Cells can be removed from early embryos and screened for genetic and chromosomal abnormalities in a procedure termed preimplantation genetic diagnosis (PGD).

1. Extra oocytes, fertilized ova and embryos from IVF procedures are stored indefinitely, donated, discarded or used in research.
2. Polar body biopsy can be used to genotype the oocyte.
3. Oocytes free of genetic disorders can be fertilized in vitro. PGD can confirm the "health" of the embryo.