Understanding Psychology (10th Ed)

R E C A P / E V A L U A T E / R E T H I N K
R E C A P 
What is the nature of development before birth?
• Each chromosome contains genes through which genetic 
information is transmitted. Genes, which are composed 
of DNA sequences, are the “software” that programs the 
future development of the body’s hardware. (p. 386)
• Genes affect not only physical attributes, but also a wide 
array of personal characteristics such as cognitive 
abilities, personality traits, and psychological 
disorders. (p. 386)
• At the moment of conception, a male’s sperm cell and a 
female’s egg cell unite; each contributes to the new indi-
vidual’s genetic makeup. The union of sperm and egg 
produces a zygote, which contains 23 pairs of chromo-
somes; one member of each pair comes from the father 
and the other comes from the mother. (p. 388)
• After two weeks the zygote becomes an embryo. By 
week 8, the embryo is called a fetus and is responsive to 
touch and other stimulation. At about week 22 it reaches 
the age of viability, which means it may survive if born 
prematurely. A fetus is normally born after 38 weeks of 
pregnancy; it weighs around 7 pounds and measures 
about 20 inches. (p. 388)
What factors can affect a child during the mother’s pregnancy?
• Genetic abnormalities produce birth defects such as 
phenylketonuria (PKU), sickle-cell anemia, Tay-Sachs 
disease, and Down syndrome. (p. 390)
• Among the environmental infl uences on fetal growth are 
the mother’s nutrition, illnesses, and drug intake. (p. 390)
E VA LU AT E
1. Match each of the following terms with its defi nition:
1. Zygote
a. Smallest unit through which genetic 
2. Gene
information is passed
3. Chromosome
b. Fertilized egg
c.
Rod-shaped structure containing 
genetic information