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Child Development, 3/e by Robert Feldman
Chapter 3
The Start of Life: Genetics and Prenatal
Development
Created by Barbara H. Bratsch
Feldman Child Development, 3/e
©2004 Prentice Hall
•What is our basic genetic endowment, and how can
human development go awry?
•How do the environment and genetics work together
to determine human characteristics?
•Which human characteristics are significantly
influenced by heredity?
•What happens during the prenatal stages of
development?
•What are the threats to the fetal environment, and what
can be done about them?
Feldman Child Development, 3/e
©2004 Prentice Hall
Genetics
• Our genetic code is stored in our genes. All genes are
composed of DNA (deoxyribonucleic acid) that determines
the nature of every cell in our bodies and how they will
function.
• 46 Chromosomes are organized into 23 pairs of DNA
portions
• A zygote is a new cell formed by fertilization
• Gametes are sex cells from the mother and father that form
a new cell at conception
Feldman Child Development, 3/e
©2004 Prentice Hall
Genetics
Feldman Child Development, 3/e
©2004 Prentice Hall
Multiple Births
• Monozygotic twins are genetically identical
and formed by one fertilized ovum that
splits
• Dizygotic twins are formed when two
separate ova are fertilized by two separate
sperm at the same time
Feldman Child Development, 3/e
©2004 Prentice Hall
Feldman Child Development, 3/e
©2004 Prentice Hall
How are boys and girls made?
• Females are made by the 23rd pair of
chromosomes that consist of XX ( an X
chromosome from the mother and an X
chromosome from the father)
• Males are made by the 23rd pair of
chromosomes and consist of an XY (an X
chromosome from the mother and a Y
chromosome by the father
Feldman Child Development, 3/e
©2004 Prentice Hall
Making a Girl
Making a Boy
Feldman Child Development, 3/e
©2004 Prentice Hall
Basics of Genetics
• Dominant trait – one trait expressed when two competing
traits are expressed
• Recessive trait – a trait present in an organism but not
expressed
• Genotype – the underlying combination of genetic
information (not outwardly visible)
• Phenotype – an observable trait
• Homozygous - Similar genes for a given trait that are
inherited from parents
• Heterozygous – Different forms of a gene for a given trait
inherited from parents
Feldman Child Development, 3/e
©2004 Prentice Hall
Phenylketonuria (PKU) – an inherited disorder in which a child
is unable to make use of phenylalanine, an essential amino acid
present in proteins found in milk and other levels. If left untreated,
PKU allows phenylalanine to build up to toxic levels and the
result can be brain damage and mental retardation
Feldman Child Development, 3/e
©2004 Prentice Hall
Feldman Child Development, 3/e
©2004 Prentice Hall
Feldman Child Development, 3/e
©2004 Prentice Hall
Gregor Mendel
pioneered experiments on pea plants that provided the foundation for the
study of genetics
Polygenic inheritance
a combination of multiple gene pairs is responsible for production of a
particular trait
X-linked genes
are recessive and located only on the X chromosome.
Hemophilia is produced by X-linked genes
Feldman Child Development, 3/e
©2004 Prentice Hall
The Human Genome
Completed in early 2001, the mapping of the
specific sequence of genes on each
chromosome was one of the most important
moments in the history of genetics
Behavioral Genetics studies the effects of
heredity on behavior
Feldman Child Development, 3/e
©2004 Prentice Hall
Feldman Child Development, 3/e
©2004 Prentice Hall
Inherited and genetic disorders
include:
• PKU
• Down syndrome
• Fragile X
syndrome
• Sickle-cell
anemia
• Tay-Sachs
disease
• Klinefelter’s
syndrome
Feldman Child Development, 3/e
©2004 Prentice Hall
•Genetic Counseling focuses on helping people deal with issues
related to inherited disorders
•Prenatal testing includes an amniocentesis in which fetal cells are
drawn out of the amniotic sac before a child is born
•Chorionic villus sampling (CVS) can be performed even earlier at 811 weeks and involves sampling of hairlike materials that surround an
embryo
•Ultrasound sonography – high frequency sound waves are used to
produce an image of the unborn child. This is less risky and invasive
than amniocentesis or CVS
Feldman Child Development, 3/e
©2004 Prentice Hall
Heredity Vs. Environment
Multifactorial transmission states that many
traits are a combination of both genetic and
environmental factors
Feldman Child Development, 3/e
©2004 Prentice Hall
How to Answer the NatureNurture Riddle
• Animal studies – breeding genetically
similar animals and determining various
environmental influences
• Human studies – studies of monozygotic
and dizygotic twins have produced data
around genetic similarities, dissimilarities
and environment
Feldman Child Development, 3/e
©2004 Prentice Hall
Feldman Child Development, 3/e
©2004 Prentice Hall
Genetics and IQ
• Genetics plays a significant role in
intelligence
• The closer the genetic link between two
individuals, the greater the correspondence
of their overall IQ scores
Feldman Child Development, 3/e
©2004 Prentice Hall
Genetics, Environment, and Personality
These traits are among the personality factors that are related
most closely to genetic factors
Feldman Child Development, 3/e
©2004 Prentice Hall
Genetics, Environment, and
Psychological Disorders
Feldman Child Development, 3/e
©2004 Prentice Hall
Schizophrenia has clear
genetic components.
The closer the genetic
links between someone
with schizophrenia and
another family member,
the more likely it is that
the other person will also
develop schizophrenia
Feldman Child Development, 3/e
©2004 Prentice Hall
Can Genes Influence the
Environment?
• Active genotype-environment effects – Situations
in which children focus on aspects of their
environment that are most congruent with their
genetically determined abilities
• Passive genotype-environment effects – Situations
in which parents’ genes are associated with the
environment in which children are raised
• Evocative genotype-environment effects –
Situations in which a child’s genes elicit a
particular type of environment
Feldman Child Development, 3/e
©2004 Prentice Hall
Prenatal Growth and Change
Fertilization, or conception, is the joining of sperm
and ovum to create the single-cell zygote
Female and Male Sex Organs
Feldman Child Development, 3/e
©2004 Prentice Hall
Giving Nature a Boost
• Infertility – inability to conceive after 12-18 months of
trying to become pregnant
• Artificial insemination – fertilization process in which a
man’s sperm is placed directly in a woman’s vagina by a
physician
• In vitro fertilization (IVF) – a procedure in which a
woman’s ova are removed from her ovaries and a man’s
sperm are used to fertilize the ova in the lab
• Surrogate mother is a woman who agrees to carry a child
to term if the mother who provides the donor eggs is
unable to conceive
Feldman Child Development, 3/e
©2004 Prentice Hall
Stages of Prenatal Development:
The Onset of Development
• Germinal - Fertilization to 2 weeks
• Embryonic - 2 weeks to 8 weeks
• Fetal stage - 8 weeks to birth
Feldman Child Development, 3/e
©2004 Prentice Hall
Feldman Child Development, 3/e
©2004 Prentice Hall
Miscarriage
spontaneous abortion
Abortion
voluntary termination of a pregnancy
Feldman Child Development, 3/e
©2004 Prentice Hall
Threats to Development
Teratogen environmental agent such as a drug, chemical, virus, or
other factor that produces a birth defect
Feldman Child Development, 3/e
©2004 Prentice Hall
Threats to Development
• Mother’s diet
• Mother’s age
• Mother’s prenatal
support
• Mother’s illness
• Mother’s drug use
• Mother’s use of
alcohol, tobacco, and
caffeine
• Father factors
Feldman Child Development, 3/e
©2004 Prentice Hall