Child Psychology: The Modern Science, 3e by Vasta, Haith, and Miller Paul J. Wellman Texas A&M University John Wiley and Sons, Inc. © 1999 PowerPoint  Presentation: Chapter 4 Genetics: The Biological Context of Development

© 1999 John Wiley and Sons, Inc. Cell Chromosomes n Cells are comprised of 3 divisions: –Cell membrane encases the cell –Cytoplasm fills the cell interior –Nucleus contains the chromosomes n Chromosomes are strands of the genetic material DNA –Each human cell contains 23 chromosome pairs (yielding 46 total chromosomes per cell) –Autosomes comprise 22 of the 23 pairs –Sex chromosomes comprise the 23rd pair Males are XY, females are XX

© 1999 John Wiley and Sons, Inc.Vasta, 3e Fig. 4.1 Divisions of the Cell

© 1999 John Wiley and Sons, Inc. Cell Function n Cells form two groups based on function: –Body cells: form the structures of the body Reproduce by mitosis: Forming two identical cells, each equipped with 23 pairs of chromosomes –Germ cells: form the reproductive cells Reproduce by meiosis: forming four cells with each cell containing only 23 chromosomes These cells are the gametes: ova or sperm During conception, a sperm merges with an ovum to form a new cell containing 23 pairs of chromosomes

© 1999 John Wiley and Sons, Inc.Vasta, 3e Fig. 4.2 n Mitosis refers to a process by which 2 identical cells are produced n Meiosis refers to a process in 4 cells are produced, with each containing only 23 chromosomes (Figure adapted with permission from Biology: Exploring Life, by G.D. Brum and L.K. McKane, 1989, New York: John Wiley and Sons)

© 1999 John Wiley and Sons, Inc.Vasta, 3e Fig. 4.3 Cross-Over During Meiosis n During meiosis, the x-shaped chromosomes line up and intermix, yielding a novel genetic product (Figure adapted with permission from Biology: Exploring Life, by G.D. Brum and L.K. McKane, 1989, New York: John Wiley and Sons)

© 1999 John Wiley and Sons, Inc.Vasta, 3e Fig. 4.4 DNA n DNA is the basic genetic material, formed from pairs of base nucleotides –The bases form pairs such as adenosine-thymine or guanine-cytosine –The DNA strand is in the form of a double helix made up of series of base pairs

© 1999 John Wiley and Sons, Inc. Principles of Heredity n Mendel argued that certain traits are transmitted from parents to child –Each trait is governed by two elements with one from each parent –Phenotype refers to the expressed trait –Genotype refers to the underlying genes that govern the trait n Principle of dominance: Some genes are always expressed, others are recessive

© 1999 John Wiley and Sons, Inc.Vasta, 3e Fig. 4.5 Mendelian Inheritance

© 1999 John Wiley and Sons, Inc. Common Genetic Traits Brown eyesBlue, gray, or green eyes Normal hairBaldness (in men) Dark hairBlond hair Color visionColor Blindness FrecklesNo freckles DimplesNo dimples DOMINANT RECESSIVE

© 1999 John Wiley and Sons, Inc. Genetic Disorders n Dominant disorders: –Huntington’s chorea refers to a fatal syndrome in which the nervous system degenerates in adulthood (age 30-40) n Recessive disorders: –Phenylketonuria (PKU) refers to an inherited disease in which the body cannot process the amino acid phenylalanine –Treatment: Eat a diet low in this amino acid during critical periods of brain development

© 1999 John Wiley and Sons, Inc.Vasta, 3e Fig. 4.8 Gene-Environment Interaction (Figure adapted with permission from “Developmental Genetics and Ontogenetic Psychology: Overdue Détente and Propositions from a Matchmaker” by I. Gottesman, In A.D. Pick (Ed.), Minnesota Symposium on Child Psychology, vol. 8, p 60. Copyright © 1974 by the University of Minnesota Press.)

© 1999 John Wiley and Sons, Inc. Gene-Behavior Studies n Four major approaches are used to study the impact of genes on behavior –Family studies –Adoption studies –Twin studies –Twins raised apart studies n Three principal areas of behavior –Intellectual abilities –Psychiatric disorders including schizophrenia –Personality

© 1999 John Wiley and Sons, Inc. Twin Studies n Twins are either derived from the same fertilized egg or a different egg –Identical twins: Monozygotic (MZ) –Fraternal twins: Dizygotic (DZ) n Twin studies compare the similarity between the twins in regard to a behavior –Concordance reflects the degree of similarity of twins on a behavior –Most studies indicate that MZ twins show greater similarity than do DZ twins and this effect is larger as they get older

© 1999 John Wiley and Sons, Inc.Vasta, 3e Fig. 4.9 Age-Related Changes in Concordance for MZ and DZ Twins (Figure adapted by permission from “The Louisville Twin Study: Developmental Synchronies in Behavior” by R.S. Wilson, 1983, Child Development, 34, p Copyright © 1983 by the Society for Research in Child Development).

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