Transcript Chapter 2

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?
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Your father determined whether you are female or male.
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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?
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You can carry the genes for a deadly illness and not become
sick yourself.
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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.
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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.
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“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