CHAPTER 3
THE BIOLOGICAL BASIS OF DEVELOPMENT
Summary Outline
I.
II.
The fertilization process
A. The beginnings
1.
The sperm
2.
The ovum (egg)
B. The menstrual cycle
1.
Ovulation
2.
Implantation
3.
Twins
C. Infertility
1.
Causes of infertility
a.
Number and quality of sperm
b.
Sexually transmitted diseases
c.
Significance of delayed childbearing
2.
Assisted reproduction
a.
Artificial insemination by donor
b.
In vitro fertilization
c.
Gamete intrafallopian transfer
d.
Zygote intrafallopian transfer
e.
Sperm and egg donation
f.
Cryopreservation
g.
Surrogate motherhood
D. In vitro fertilization
1.
Procedural steps
2.
Success rate
E. Adoption
1.
Closed adoption
2.
Open adoption
3.
Embryo adoption
4.
Foreign adoption
Heredity at work
A. Cell division
1.
Mitosis
2.
Meiosis
B. Chromosomes and genes
1.
23 pairs of genes
2.
Females genetically stronger than males
3.
Genetic information
a.
genotype
b.
phenotype
C. The DNA: Structure and function
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D.
E.
F.
1.
Adenine
2.
Guanine
3.
Cytosine
4.
Thymine
How traits are transmitted
1.
Heterozygous and homozygous
2.
Dominant and recessive
3.
Principle of segregation mutations
4.
Codominant and incomplete
5.
Polygenic inheritance
Hereditary disorders
1.
Chromosomal disorders
a.
Down syndrome
b.
Klinefelter syndrome
c.
Turner syndrome
2.
Genetic disorders
a.
Tay-Sachs disease
b.
Sickle-cell anemia
c.
Cystic fibrosis
d.
Phenylketonuria (PKU)
e.
Spina bifida
f.
Sex-linked inheritance
(1) Hemophilia
(2) Fragile X syndrome
The Human Genome Project
1.
How the Human Genome Project began
2.
Ethical, legal, and social implications
a.
Fairness
b.
Privacy and confidentiality
c.
Psychological impact
d.
Genetic testing
e.
Reproductive issues
f.
Clinical issues
g.
Commercialization
Learning Objectives
After reading this chapter, the student should be able to complete the following goals:
1.
Describe the role of the sperm and the ovum in reproduction.
2.
Explain the relationship of the menstrual cycle to the production and fertilization of the
ovum.
3.
Define dizygotic and monozygotic twins and cite the incidence of twins.
4.
List the most common causes of infertility and examine techniques available to help
infertile couples.
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5.
Distinguish between closed adoption and open adoption and place the change within a
historical context.
6.
Discuss the recent developments in embryo and foreign adoption.
7.
Differentiate between meiosis and mitosis and explain the function of each in human
growth and reproduction.
8.
Differentiate between chromosomes and genes.
9.
Define phenotype and genotype.
10.
Describe the basic structure of DNA and discuss its role in human reproduction.
11.
Differentiate when a person is homozygous and heterozygous for a trait.
12.
Describe chromosomal arrangement and cite conclusions regarding male and female
chromosomal makeup.
13.
Identify and describe three chromosomal disorders.
14.
Identify and describe five genetic disorders.
15.
Define sex-linked inheritance and provide examples.
16.
State the major features and anticipated uses of the Human Genome Project
17.
Summarize the ethical, legal, and social implications of the Human Genome Project.
Key Terms
alleles
blastocyst
closed adoption
cystic fibrosis (CF)
cytogenetics
deoxyribonucleic acid (DNA)
dizygotic
dominant
Down syndrome
endometriosis
fallopian tubes
fragile X syndrome
genotype
hemophilia
heterozygous
homozygous
Human Genome Project
implantation
in vitro fertilization (IVF)
Klinefelter syndrome
meiosis
mitosis
monozygotic
mutations
open adoption
ovulation
phenotype
phenylketonuria (PKU)
polygenic inheritance
recessive
sex-linked inheritance
sickle-cell anemia
spina bifida
Turner syndrome
zygote
Lecture Suggestions
1.
Reproduction Variations
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The demand for artificial methods of creating life has risen dramatically as infertility rates have
skyrocketed. One in six American couples is affected with infertility. For women, the most
common reason for infertility is a blockage or abnormality of the fallopian tubes. For men, a low
sperm count or low sperm motility affects as many as 10 million. The development of the
world’s first test tube baby, Louise Brown, was one of the most important advances in
reproductive engineering. This technique permits couples who are infertile or who have problems
that block fertilization to have children.
Discuss current medical technology that is used to counteract infertility, including fertility drugs,
in vitro fertilization, surrogate mothers, and artificial insemination. Discuss the advantages and
disadvantages of advanced medical technology and pose ethical questions. Discuss genetic
engineering and genetic counseling, biological bases of behavior, and family planning.
2.
Reproductive Technology and Case Law
With new advances in reproductive technology, courts are facing new dilemmas. Recently, case
law has addressed the issue of cryopreservation—the freezing of embryos for future use. At issue
is ownership of the frozen embryos. Several legal cases involve once happily married couples
who, for various reasons, selected to freeze embryos. These couples, now divorced, are in the
courts trying to determine legally who has rights to the frozen embryos. In some cases, one
member of the divorced couple wants to implant a frozen embryo (for the woman implantation
would occur in herself, for the man implantation in another partner or surrogate mother), while
the other partner wants the embryos destroyed or donated to someone else.
Discuss with students the advantages and disadvantages of cryopreservation as a reproductive
technique. What legal and ethical questions arise when a couple is no longer married or together
and does not agree on ownership of the frozen embryos or how to use them?
3.
Methods Used by Behavior Geneticists
In order to study heredity’s influence on development, behavior geneticists often use either the
adoption study or the twin study method.
In the adoption study method, correlations between adopted children and their biological and
adoptive parents are compared. The adoptive parents and the adopted child share environments
but no genes; therefore, any similarities found are assumed to be caused by environmental
factors. On the other hand, biological parents and the adopted child share genetic inheritance but
do not share the environment; therefore, any similarities found are the result of genetic factors.
In the twin study method, the concordance rate between monozygotic (identical) and dizygotic
(nonidentical) twins is compared. Because monozygotic twins come from the same fertilized
zygote, they share all of their genes. But dizygotic twins, who come from two eggs, are no more
genetically alike than are siblings. Therefore, the concordance rate between monozygotic twins
should be greater than that for dizygotic twins. The twin study method assumes that the
environment is equivalent for the twins. But one criticism of the twin study method is that
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perhaps parents create differences found in monozygotic twins; therefore, similarities found in
monozygotic twins may be caused by environmental influences, rather than genetic inheritance.
Following a broad overview of behavior genetics, discuss adoption and twin studies conducted
on intelligence, personality, and psychopathology. Elicit from students why both types of studies
are needed, the difficulties in such studies, and how adoption and twin studies differ.
4.
DNA and Cloning
Recent research on DNA has resulted in scientists’ ability to clone animals. In 1997, Dolly the
sheep became the first example of successful animal cloning. Discuss with students the issue of
cloning. Ask students to share their attitudes and knowledge about cloning. Does cloning have
scientific value? What issues does it raise for human reproduction?
Instructor’s CD-ROM Resource Activities
1.
Chapter 4 Biology
D.
The Pros and Cons of Genetic Testing
E.
Visiting an Infertility Web Site
F.
Genetic Counseling
H.
Chromosomal Abnormalities
Classroom or Student Activities
1.
Cystic Fibrosis
Cystic fibrosis is a severe and deadly genetic disease affecting 1 in 1,200 children. The gene that
causes cystic fibrosis has been identified, but research needs to continue. Arrange to have a
researcher from an area college or university who is studying cystic fibrosis deliver a guest
lecture in your class. Ask the researcher to discuss current research on the disease. A family with
a child who has cystic fibrosis can also be invited to give students an understanding of the
personal impact of the disease.
2.
Adoption
In your community, make arrangements to have two families visit your class. One family should
have adopted a child or children of the same race and culture as the adoptive parents. Locate a
second family that has adopted a child or children who are of a different race from the adoptive
parents or from another country. Have students prepare questions before class that address the
adoption experience for these families.
An alternative activity is to have a family visit your class and share its open adoption experience.
If possible, arrange to have both the biological and adoptive parents present. As a supplement or
substitute, a local adoption agency official could present information on closed and open
adoption procedures.
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3.
Genotype and Phenotype
Ask students to review the definitions of genotype and phenotype. Genotype refers to the genetic
makeup of an individual, and phenotype refers to the actual observed characteristics of a person.
Ask students to discuss how a child’s phenotype may differ from his or her genotype and the
impact of the environment on heredity. For instance, if a child has a genotype for high
intelligence, what factors in his or her environment will hinder emerging potential?
4.
Career-Related Activities
A. Imagine that you are working as an administrative assistant in a family planning clinic.
You’ve been asked to make a wall chart for the lobby that describes genetic and chromosomal
disorders, with signs and symptoms, frequency of occurrence, and any known treatments.
B. Imagine that you are working as a high school health teacher. You are developing your
curriculum unit on infertility. Make an outline for your lecture and class discussion on both the
facts and the ethical issues of assisted reproduction, including in vitro fertilization, GIFT, ZIFT,
egg and sperm donation, surrogacy, and adoption.
Questions for Review and Discussion
1.
Discuss what science knows about twins, including the different types of twins, how often
twins occur, what factors influence the chance of having twins, and what we know about
twin intelligence quotients (IQs).
2.
Review the causes of infertility and discuss the options available to infertile couples.
3.
Discuss the processes of adoption and review the issues that families must deal with in
cases of international adoptions. What are the special challenges facing these families?
4.
Explain mitosis and meiosis and show how each contributes to human growth and
development.
5.
Give examples that explain the statement, “Genes always function in an environment, and
environmental circumstances affect the way the genes express themselves.”
6.
Review the different genetic (hereditary) disorders and discuss the causes and outcomes of
each disease.
7.
Demonstrate the way dominant and recessive characteristics are passed from one generation
to the next by extending the example presented in the text (of brown and blue eyes) to the
next generation.
8.
Review the recent development of the Human Genome Project. What are the implications
for you personally?
9.
Explain the interaction between genotype and phenotype.
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Web Site Resources
Child Development
www. srcd.org
Developmental Psychology
www.apa.org/journals/dev.html
Institute for Behavioral Genetics
http://ibgwww.colorado.edu
Centers for Disease Control, Environmental
Health, Birth Defects and Developmental
Disabilities
www.cdc.gov/healthyplaces
Infants, Babies, Children, and Childbirth
http://www.moonlily.com/parents/
Human Genome Project
www.ornl.gov/TechResources/Human_Genom
e/home.html
Embryonic Development Images
www.mhhe.com/links/1253/556/554
Genetics
www.med.jhu.edu/Greenberg.Center/tutorial
Genetic Disorders
http://www.nlm.nih.gov/medlineplus/geneticdis
orders.html
Genetic Disorders
www. noah-health.org/english/illness/
genetic_diseases/geneticdis.html
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