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Child Psychology A Canadian Perspective THIRD EDITION Younger, Adler, Vasta.

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Presentation on theme: "Child Psychology A Canadian Perspective THIRD EDITION Younger, Adler, Vasta."— Presentation transcript:

1 Child Psychology A Canadian Perspective THIRD EDITION Younger, Adler, Vasta

2 Chapter 3 Genetics: The Biological Context of Development Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 2

3 Learning Objectives Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Learning Objective 3.1: Learning Objective 3.1: Identify and describe the mechanisms and processes by which physical and behavioural characteristics are inherited. Identify and describe the mechanisms and processes by which physical and behavioural characteristics are inherited. Learning Objective 3.2: Learning Objective 3.2: Describe different types of genetic disorders and their impact on child development. Describe different types of genetic disorders and their impact on child development. Learning Objective 3.3: Learning Objective 3.3: Describe the influence that genes have on the development of psychological abilities and traits. Describe the influence that genes have on the development of psychological abilities and traits. Learning Objective 3.4: Learning Objective 3.4: How do genes and environment interact to influence the development of behaviour? How do genes and environment interact to influence the development of behaviour? 3

4 Mechanisms of Inheritance: Cell Division Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Cells are comprised of three divisions Cells are comprised of three divisions Nucleus contains the chromosomes Nucleus contains the chromosomes Chromosomes: strands of the genetic material DNA Chromosomes: strands of the genetic material DNA Each human cell contains 23 chromosome pairs (yielding 46 total chromosomes per cell) Each human cell contains 23 chromosome pairs (yielding 46 total chromosomes per cell) Autosomes comprise 22 of the 23 pairs Autosomes comprise 22 of the 23 pairs Sex chromosomes comprise the 23rd pair Sex chromosomes comprise the 23rd pair Males are XY, females are XX Males are XY, females are XX Cytoplasm fills the cell interior Cytoplasm fills the cell interior Cell membrane encases the cell Cell membrane encases the cell 4

5 Mechanisms of Inheritance: Cell Division Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Cells form two groups based on function Cells form two groups based on function Body cells: form the structures of the body Body cells: form the structures of the body Reproduce by mitosis Reproduce by mitosis Forming two identical cells, each equipped with 23 pairs of chromosomes Forming two identical cells, each equipped with 23 pairs of chromosomes Germ cells: form the reproductive cells Germ cells: form the reproductive cells Reproduce by meiosis Reproduce by meiosis Forming four cells with each cell containing only 23 chromosomes Forming four cells with each cell containing only 23 chromosomes These cells are the gametes (ova or sperm) 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 During conception, a sperm merges with an ovum to form a new cell containing 23 pairs of chromosomes 5

6 Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Mitosis refers to a process by which 2 identical cells are produced Meiosis refers to a process in 4 cells are produced, with each containing only 23 chromosomes Figure 3.1: (Mitosis and meiosis). Mitosis results in two cells identical with the parent and with each other. Meiosis results in four cells different from the parent cell and from each other. Adapted from Biology: Exploring Life (p.152) by G. D. Brum & L. K. McKane, 1989, New York: John Wiley & Sons. Adapted by permission of the authors. 6

7 Mechanisms of Inheritance: Cell Division Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Figure 3.2 Crossing over results in the exchange of genetic material. After the cross-over, all four strands are different. Adapted from Biology: Exploring Life (p. 44) by G. D. Brum & L. K. McKane, 1989, New York: John Wiley & Sons. Adapted by permission of the authors. Crossing over: During meiosis, the x-shaped chromosomes line up and intermix, yielding a novel genetic product 7

8 Inside the Chromosome Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Figure 3.3: Structure and Replication of DNA DNA: the basic genetic material, formed from pairs of base nucleotidesDNA: the basic genetic material, formed from pairs of base nucleotides The bases form pairs such as adenosine-thymine or guanine-cytosine 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 a series of base pairs The DNA strand is in the form of a double helix made up of a series of base pairs 8

9 Mendel’s Studies: Principles of Heredity Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Mendel argued that certain traits are transmitted from parents to childMendel argued that certain traits are transmitted from parents to child Each trait is governed by two elements with one from each parentEach trait is governed by two elements with one from each parent Phenotype: Expressed trait Phenotype: Expressed trait Genotype: Underlying genes that govern the trait Genotype: Underlying genes that govern the trait 9

10 Mendel’s Studies: Principles of Genetic Transmission Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Principle of dominance: Principle of dominance: Some genes are always expressed (dominant gene), others are recessive (recessive gene) Some genes are always expressed (dominant gene), others are recessive (recessive gene) Polygenic inheritance: Polygenic inheritance: Occurs when traits are determined by a number of genes Occurs when traits are determined by a number of genes Incomplete dominance: Incomplete dominance: Occurs when the dominant gene does not completely suppress the recessive gene Occurs when the dominant gene does not completely suppress the recessive gene Codominance: Codominance: Occurs when both genes are dominant and thus both are expressed Occurs when both genes are dominant and thus both are expressed 10

11 Mendel’s Studies: Common Genetic Traits Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 DominantRecessive Brown eyes Blue, gray, or green eyes Normal hair Baldness (in men) Dark hair Blond hair Normal colour vision Colour blindness Freckles No freckles Dimples Free earlobes Double-jointed thumbs No dimples Attached earlobes Tight thumb ligaments 11

12 Genetic Disorders: Hereditary Disorders Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Mutations (genetic variations) can be adaptive or maladaptiveMutations (genetic variations) can be adaptive or maladaptive Dominant disorders Dominant disorders Huntington’s chorea: Huntington’s chorea: Fatal syndrome in which the nervous system degenerates in adulthood (age 30-40)Fatal syndrome in which the nervous system degenerates in adulthood (age 30-40) 12

13 Genetic Disorders: Hereditary Disorders Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Recessive disorders Recessive disorders Diseases with errors of metabolism Diseases with errors of metabolism Tay-Sachs disease: Tay-Sachs disease: Fatal disease in which the nervous system disintegrates because the body cannot break down fats in brain cells Fatal disease in which the nervous system disintegrates because the body cannot break down fats in brain cells Phenylketonuria (PKU): Phenylketonuria (PKU): Inherited disease in which the body cannot process the amino acid phenylalanine 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 Treatment: Eat a diet low in this amino acid during critical periods of brain development Diseases without errors of metabolismDiseases without errors of metabolism Sickle-cell anemia (SCA) Sickle-cell anemia (SCA) 13

14 Sickle-Cell Anemia (SCA) Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 314 Figure 3.4: Scanning electron micrographs of red blood cells from normal individuals (left) and individuals with sickle-cell anemia (right). (Bill Longcore, Photo Researchers, Inc.)

15 Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 315 Genetic Disorders Differences between the two sex chromosomes have implications for the transmission of certain disorders called X-linked disorders X-linked disorders: disorders that result from recessive genes located on the X chromosome, leaving males more vulnerable to them Example: hemophelia—bleeding disorder caused by low or no blood protein essential for clotting; results from a recessive allele on the X chromosome Other examples of X-linked disorders: Duchenne muscular dystrophy, red-green colour blindness, and fragile X syndrome

16 Structural Defects in the Chromosome Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 316 Autosomal disorders: Autosomal disorders: Down syndromeDown syndrome 21st pair of chromosomes has a third member 21st pair of chromosomes has a third member Results in mental retardation, poor muscle tone, and distinctive facial features Results in mental retardation, poor muscle tone, and distinctive facial features Greatest risk occurs in mothers between the ages of years Greatest risk occurs in mothers between the ages of years

17 Structural Defects in the Chromosome Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 317 Disorders of the sex chromosomes: Disorders of the sex chromosomes: Fragile X syndrome: Fragile X syndrome: Caused by an abnormal gene on the X chromosome Caused by an abnormal gene on the X chromosome Results in a variety of physical and behavioural symptoms, including mental retardation Results in a variety of physical and behavioural symptoms, including mental retardation Turner’s syndrome: Turner’s syndrome: Occurs when a female has only one X chromosome (XO) Occurs when a female has only one X chromosome (XO) Klinefelter’s syndrome: Klinefelter’s syndrome: Occurs when a male inherits an extra X chromosome (XXY) Occurs when a male inherits an extra X chromosome (XXY)

18 Studying the Effects of Genes on Behaviour Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Three principal areas of behaviour Three principal areas of behaviour Intellectual abilities Intellectual abilities Psychiatric disorders (including children’s behavioural problems) Psychiatric disorders (including children’s behavioural problems) Personality Personality Four major approaches are used to study the impact of genes on behaviour Four major approaches are used to study the impact of genes on behaviour Family studies Family studies Adoption studies Adoption studies Twin studies Twin studies Combined Twin Study and Adoption Study Combined Twin Study and Adoption Study 18

19 Family and Adoption Studies Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Family studies: Family studies: Compare different family members and their similarity in certain characteristics Compare different family members and their similarity in certain characteristics Explore whether the phenotypic similarity on a trait follows the genotypic similarity among the people being compared Explore whether the phenotypic similarity on a trait follows the genotypic similarity among the people being compared Adoption studies: Adoption studies: Compare similarities in characteristics between adopted children and their biological and adoptive parents Compare similarities in characteristics between adopted children and their biological and adoptive parents Explores the contribution of shared genes versus shared environment to a trait Explores the contribution of shared genes versus shared environment to a trait 19

20 Twin Studies Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Two types of twins: Two types of twins: Identical twins – Monozygotic (MZ) Identical twins – Monozygotic (MZ) From the same fertilized egg From the same fertilized egg Fraternal twins – Dizygotic (DZ) Fraternal twins – Dizygotic (DZ) From two different eggs From two different eggs Twin studies:Twin studies: Compare the similarity between the twins in regard to a behaviour Compare the similarity between the twins in regard to a behaviour Concordance: the degree of similarity of twins on a behavior Concordance: 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 Most studies indicate that MZ twins show greater similarity than do DZ twins and this effect is larger as they get older 20

21 Twin Studies Age-Related Changes in Concordance for MZ and DZ Twins Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 321 Figure 3.7: Concordance in IQ changes in (a) identical, or monozygotic (MZ), twins and (b) fraternal, or dizygotic (DZ), twins from 3 months to 6 years of age.The scales are different to accommodate different ranges of scores.The important point is that changes in performance are more similar for monozygotic twins. Adapted from “The Louisville Twin Study: Developmental Synchronies in Behavior” by R. S.Wilson, 1983, Child Development, 54, p Copyright © 1983 by The Society for Research in Child Development, Inc. Adapted by permission.

22 Models of Gene-Environment Interaction Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Gottesman’s limit-setting model: Gottesman’s limit-setting model: Range of ability is determined by genes— actual value of that ability is determined by the environment (range of reaction) Range of ability is determined by genes— actual value of that ability is determined by the environment (range of reaction) 22

23 Range of Reaction Model Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 323 Figure 3.8: The reaction range concept, showing the simultaneous influences of genes and environment. Adapted from “Developmental Genetics and Ontogenetic Psychology: Overdue Détente and Propositions from a Matchmaker” by I. I. Gottesman, In A. D. Pick (Ed.), Minnesota Symposia on Child Psychology, vol. 8, p. 60, University of Minnesota Press. Copyright © 1974 by the University of Minnesota. Adapted by permission.

24 Models of Gene-Environment Interaction Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Scarr’s niche-picking model: Scarr’s niche-picking model: Passive gene-environment correlation Passive gene-environment correlation Evocative gene-environment correlation Evocative gene-environment correlation Active gene-environment correlation Active gene-environment correlation Plomin’s environmental genetics model: Plomin’s environmental genetics model: Different children experience the same environment differently (nonshared environment) Different children experience the same environment differently (nonshared environment) Bronfenbrenner and Ceci’s biological model: Bronfenbrenner and Ceci’s biological model: Child’s genes and immediate environment interact Child’s genes and immediate environment interact 24

25 Younger, Adler, Vasta/Child Psychology, Third Edition, Chapter 3 Copyright © 2012 John Wiley & Sons Canada, Ltd. All rights reserved. Reproduction or translation of this work beyond that permitted by Access Copyright (the Canadian copyright licensing agency) is unlawful. Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd. The purchaser may make back-up copies for his or her own use only and not for distribution or resale. The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these files or programs or from the use of the information contained herein. 25


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