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The Development Of Children
Chapter 2
The Human Heritage:
Genes and the Environment
Bottom Line 1 Terms to know in Ch 2
• Mitosis and Meiosis
• Chromosomes: Males have XY and
Females have XX chromosomes
• Genes
• DNA
• Dominant and Recessive Genes
Bottom Line 2
Concepts to know in Ch 2
• Genetics + Environment = Characteristics
Sex-linked characteristics
• Gene-environment interaction - bunnies!
• Genes and behavior - family, twin and
adoption studies
• Causes of Genetic Abnormalities (Down
Syndrome, PKU, Sickle Cell anemia,
Klinefelter Syndrome)
Down Syndrome
• Cause: 3 (vs. 2) copies of
chromosome 21
• Traits:
Mentally/physically
retarded and distinctive
physical characteristics
• Incidence: 1:1000 births
• Outlook: Special
education markedly
improve intellectual,
social, physical and
creative functioning
Phenylketonuria (PKU)
• Cause: Defective recessive gene resulting
in retarded development of prefrontal
cortex
• Traits: Severe retardation
• Incidence: 1:10,000
• Outlook: Feeding PKU
infants a diet avoiding
milk, eggs, bread, fish
reduces the severity of
mental retardation
Sickle-Cell Anemia
• Cause: Recessive gene
(victims are homozygous, but
heterozygous subjects are
also mildly affected)
• Traits: Abnormal blood cells
cause circulatory problems
(e.g., heart enlargement) and
severe anemia
• Incidence: 8-9% of U.S.
blacks
• Outlook: Crippling, but
treatable with medication
Klinefelter Syndrome
• Cause: Extra X chromosome
(i.e., XXY)
• Traits: Males fail to develop
secondary sex characteristics
(e.g., facial hair, voice change),
are sterile, and most have
speech and language problems
• Incidence: 1:900 males
• Outlook: May be treatable with
testosterone replacement therapy
Survival Strategies: Culture
• Cultural artifacts, such as tools
and clothing, greatly extend the
range of environments in which
human beings can reproduce
and thrive
• Cultural knowledge, such as the
creation of “hazard prevention
strategies,” serves to protect
and support children to enable
them to mature and reproduce