831
CHAPTER TWENTY-TWO
Reproductive System
EGGS FOR SALE
Case reports point to ovary scarring and possibly even cancer. Another side
ef
ect that Sherrie had not Fully considered was how she would Feel aFterward.
Although she was happy to have helped the couple and to have paid her tuition,
she Feared she would always wonder about the twins her eggs had become.
T
he ad in the student newspaper seemed too good to be
true—the Fee For donating a Few eggs would pay nearly a
semester’s tuition. Intrigued, the young woman submitted a
health history, had a checkup, and a month later received a
call. A young couple struggling with inFertility sought an egg
donor. They’d chosen Sherrie because, with her strawberry-blond hair, she
looked like Linda, the woman whose cancer had leFt her unable to conceive.
The donor eggs would be Fertilized in a laboratory dish (
in vitro
) with sperm
From Linda’s partner, and then implanted in Linda’s uterus.
±or two weeks Sherrie injected herselF in the thigh with a drug that acts
like gonadotropin-releasing hormone, suppressing release oF an egg From an
ovary (ovulation). When daily hormone checks indicated that her endocrine
system was in sync with Linda’s, Sherrie began giving herselF shots twice a
day at the back oF the hip. This second drug mimicked Follicle-stimulating
hormone, and it caused several ovarian Follicles to mature. ±inally, injections
oF luteinizing hormone brought the eggs to Full maturity. Then, at a health-
care Facility, Sherrie was given pain medication and light sedation. A needle
was inserted through her vaginal wall to remove a dozen oF the most mature
eggs as they swelled to the surFace oF her ovary. This is the least invasive way
to retrieve eggs.
Two
in vitro
Fertilized ova divided a Few times, Forming an early embryo,
and were then implanted into Linda’s uterus. The rest were Frozen, For possi-
ble later use. The preparation and procedure weren’t too painFul. Sherrie had
Felt a dull aching the last day, and Felt bloated For a Few days aFter the egg
retrieval, but she did not experience bleeding, inFection, cramping, or mood
swings. Nor did she develop a complication in which too many eggs mature,
causing ²
uid to leak From blood vessels and accumulate in the abdomen.
About 6% oF egg donors develop the syndrome, which can cause inFertility,
kidney Failure, and even death. ±uture risks, however, are uncertain, because
eggs haven’t yet been collected long enough to know the consequences.
Ads in student newspapers seek egg donors For inFertile couples. The protocol is
uncomFortable and takes several weeks. Pay is high, and is oFten based on SAT
scores, college grades, and even the reputation oF a particular university.
22.1
INTRODUCTION
The male and female reproductive systems are connected
sets of organs and glands. Some of the reproductive organs
and glands secrete hormones vital to the development and
maintenance of secondary sex characteristics and the regula-
tion of reproductive functions. Reproductive organs produce
and nurture sex cells and transport them to sites of fertiliza-
tion. Male sex cells are
sperm.
Female sex cells are eggs, or
oocytes
(o
o-sı¯tz), which in Latin means “egg cells.” These
cells are produced by a special type of cell division called
meiosis
(mi-o
sis).
Meiosis includes two successive divisions, called the
first
and
second meiotic divisions.
The first meiotic divi-
sion (meiosis I) separates homologous chromosome pairs.
Homologous pairs are the same, gene for gene. They may not
be identical, however, because a gene may have variants,
and the chromosome that comes from the person’s mother
may carry a different variant for the corresponding gene
from the father’s homologous chromosome. Before meiosis
I, each homologous chromosome is replicated, so it consists
of two DNA strands called
chromatids.
Each chromatid has
the complete genetic information associated with that chro-
mosome. The chromatids of a replicated chromosome attach
at regions called
centromeres.
Each of the cells that undergoes the second meiotic divi-
sion (
meiosis II
) emerges with one member of each homolo-
gous pair, a condition termed
haploid.
That is, a haploid cell
has one set of chromosomes. This second division separates
the chromatids, producing cells that are still haploid, but whose
chromosomes are no longer in the replicated form. After meio-
sis II, each of the chromatids is an independent chromosome.
The steps of meiosis are clearer when considered in a
time sequence
(f
g. 22.1)
. However, keep in mind that, like
mitosis, meiosis is a continuous process. Considering it in
steps makes it easier to follow.
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