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Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Chapter 2 Heredity and Conception Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Heredity and Conception: Truth or Fiction? Your father determined whether you are female or male. Brown eyes are dominant over blue eyes. Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Heredity and Conception: Truth or Fiction? You can carry the genes for a deadly illness and not become sick yourself. Identical twins are more likely than fraternal twins to share disorders such as schizophrenia and vulnerability to alcoholism. Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Heredity and Conception: Truth or Fiction? 120 to 150 boys are conceived for every 100 girls. Sperm travel about at random inside the woman’s reproductive tract, so that reaching the ovum is a matter of luck. Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Heredity and Conception: Truth or Fiction? Extensive athletic activity may contribute to infertility in the male. “Test-tube” babies are grown in a laboratory dish throughout their nine-month gestation period. Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Heredity and Conception: Truth or Fiction? You can select the sex of your child. Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 The Influence of Heredity on Development The Nature of Nature Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 What Is Meant by Heredity? • Heredity – Defines one’s nature • Genetics – Field within the science of biology that studies heredity • Genetic influences – Physical traits – Behavioral traits – Psychological disorders Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 What Are Chromosomes and Genes? • Chromosomes – Found in cells – 23 pairs of rod-like structures • Genes – Segments within chromosomes – Regulate development of traits • DNA – Large strands make up genes – Double spiral (helix) – Composed of phosphate (P), sugars (S), and base pairs Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Figure 2.1 Cells, Chromosomes, and DNA Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 What Happens During Cell Division? • Mitosis – Cell division by which growth occurs – Strands of DNA break apart and are rebuilt – Result is identical copies of DNA strand Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Figure 2.2 Mitosis Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 What Happens During Cell Division? • Meiosis – Cell division by which sperm and ova are produced – 23 chromosome pairs divide – Result is new cell with only 23 chromosomes • 23 pairs are autosomes • 23rd pair determines gender; X from mother and X or Y from father Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 How Are Twins Formed? • Monozygotic Twins (MX) – Derived from a single zygote that has split in two – Genetically identical • Dizygotic Twins (DZ) – Derived from two zygotes – Share 50% of genetic material Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 How Do Genes Determine Traits? • Traits are determined by alleles – Pair of genes • Homozygous – Alleles for a trait are the same • Heterozygous – Alleles for a trait are different Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Dominant and Recessive Traits: Mendel’s Laws of Heredity • Averaging – Effects of both alleles are shown – Incomplete dominance and codominance • Law of Dominance – Dominant allele paired with recessive allele • Dominant allele appears in child Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Figure 2.4 Transmission of Dominant and Recessive Traits Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Table 2.1 Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Chromosomal Abnormalities: Down Syndrome • Cause: extra chromosome on 21st pair • Probability increases with increased age of parent • Characteristics of children – Facial features – Cognitive and physical deficiencies • Adjustment of children Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Table 2.2 Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Chromosomal Abnormalities: Sex Linked • Male with extra sex chromosome – XYY - extra Y chromosome – XXY - Klinefelter syndrome • Female with abnormal number of sex chromosomes – X - Turner syndrome – XXX - Triple X syndrome Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Genetic Abnormalities • Recessive gene abnormalities – PKU (phenylketonuria) – Sickle-Cell Anemia – Tay-Sachs disease – Cystic Fibrosis Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Genetic Abnormalities • Dominant gene abnormalities – Huntington’s disease • Sex-linked abnormalities – Hemophilia – Duchenne muscular dystrophy Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Genetic Counseling and Prenatal Testing • Genetic Counseling – Addresses probability of genetic abnormalities Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Genetic Counseling and Prenatal Testing • Amniocentesis – Routine among American women over age 35 – Used to detect over 100 chromosomal and genetic abnormalities – Indicates the sex of the baby – Some risk of miscarriage Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Figure 2.6 Amniocentesis Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Genetic Counseling and Prenatal Testing • Chorionic Villus Sampling (CVS) – Can diagnosis abnormalities earlier than amniocentesis – Slightly greater risk of spontaneous abortion • Ultrasound – Sonogram “picture” of fetus – Beneficial in determining position of fetus • Blood Tests – Alpha-Fetoprotein (AFP) assay Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Lessons in Observation: Prenatal Assessment Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Lessons in Observation: Prenatal Assessment • What is the most common chromosomal abnormality seen in liveborn babies? • Is an amniocentesis recommended for Eleanor? Why or why not? Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Lessons in Observation: Prenatal Assessment • According to the ultrasound results, what is the position of the baby? • Describe the two structural abnormalities and/or marker of chromosomal abnormalities discussed as the ultrasound is performed. Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Lessons in Observation: Prenatal Assessment • What risks are associated with various prenatal assessment measures? • How prevalent are birth defects resulting from genetic factors? Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Lessons in Observation: Prenatal Assessment • What are some other, non-genetic factors that can affect prenatal development? • Eleanor took some careful planned actions (taking vitamins and eliminating alcohol consumption). What problems will this likely rule out? Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Heredity and the Environment Nature versus Nurture Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 What Is the Difference Between Our Genotypes and Our Phenotypes? • Genotypes – Set of traits inherited from parents • Phenotypes – Actual sets of traits – product of genetics and environment Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Using Research to Sort Out the Effects of Genetics and Environmental Influences on Development • Kinship studies – Genetic closeness of relatives • Twin Studies – Monozygotic twins share 100% of genes – Dizygotic twins share 50% of genes (same as other siblings) – Reared together versus reared apart • Adoption studies Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Conception Against All Odds Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Conception: Against All Odds • Ova – Begin to mature at puberty – Monthly release of mature egg into Fallopian tube – Egg is propelled by cilia – If not fertilized, egg is discharged in the menstrual flow Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Conception: Against All Odds • Sperm – Self propelled, and smaller than ova – Sperm with Y chromosome swim faster than sperm with X chromosome – From 200 to 400 million in ejaculate; only 1 in 1,000 arrive in vicinity of ovum – Sperm are attracted by chemical odor secreted by ova Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Figure 2.9 Female Reproductive Organs Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 What Process Brings Together the Genes From Each Parent? • Only one sperm enters the zona pellucida – Sperm secrete enzyme hyaluronidase to allow penetration of the zona pellucida – When one sperm enters, the zona pellucida thickens, locking out other sperm • Chromosomes from sperm and egg combine to form 23 new pairs Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Infertility and Other Ways of Becoming Parents: What Are the Causes of Infertility? • Major fertility problems among men – Low sperm count – Deformed sperm – Low sperm motility – Infections diseases – Direct trauma to testes • Causes – Genetic factors, environmental poisons, diabetes, STI’s, overheating testes, pressure to testes, aging and effects of drugs Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Infertility and Other Ways of Becoming Parents: What Are the Causes of Infertility? • Major fertility problems among women – Failure to ovulate • Fertility drugs are used to cause women to ovulate – Infections • Pelvic inflammatory disease (PID) – Endometriosis • Obstruct Fallopian tubes – Barriers of disorders in passageways (i.e., Fallopian tubes) Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Infertility and Other Ways of Becoming Parents: How Are Couples Helped to Have Children? • Artificial insemination – Sperm injected into mother’s uterus • In Vitro Fertilization – Ova and sperm are fertilized, then implanted in mother’s uterus • Donor IVF – Ovum harvested from donor woman; fertilized in vitro and implanted in recipient’s uterus Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Infertility and Other Ways of Becoming Parents • Surrogate Mothers – Surrogate “substitutes” bring babies to term for another woman • Adoption – Option chosen by singles and infertile couples Childhood and Adolescence: Voyages in Development, Second Edition, Spencer A. Rathus Chapter 2 Selecting the Sex of Your Child • Cultural Folklore • Sperm-Separation Procedures • Preimplantation Genetic Diagnosis (PGD) • Moral and Ethical Questions