Download Chapter 3 Outline

Chapter 3 Outline
I. Becoming Parents
A. Conception
1. Changing Theories of Conception
 Two-seed theory: (Hippocrates) Joining of male and female seeds. There are
no
significant anatomical differences between male and female genitalia except
that men’s are located outside the body and women’s are located inside the
body. Theory remained influential until 17 th century in England.
 Female as Defective Theory: (Aristotle) Sperm is responsible for conception.
Females resulted when development was disturbed.
 Animalculists: Little people are contained in the heads of sperm which grow
when deposited in the womb.
 Ovists: Female ovaries contain tiny, already formed humans whose growth is
activated by male sperm.
2. How Fertilization Takes Place
 Fertilization: Union of sperm and ovum fuse to produce a single new cell
called a zygote; also called conception.
 Gametes: Sex cells.
 Zygote: One celled organism resulting from fertilization.
 Follicle: Small sac which holds ovum.
 Ovulation: Rupture of a mature follicle in ovary and expulsion of its ovum.
Occurs about once every 28 days until menopause.
 Cilia: Small hair cells that sweep the ovum along the fallopian tube.
 Cervix: Opening of the uterus.
B. Infertility
 Infertility: Inability to conceive after 12 months of trying.
1. Causes of Infertility
 Most common cause of infertility in men is low sperm count.
 Most common cause of infertility in women is blockage of the fallopian tubes.
2. Alternative Ways to Parenthood
 Assisted reproductive technology (ART)
o In vitro fertilization (IVF): Fertilization done outside mother’s body.
o In vitro maturation (IVM): Harvesting of follicles before ovulation is
complete.
o Intracytoplasmic sperm injection (ISI):A single sperm is injected into the
ovum.
o Artificial insemination: Injection of sperm into a woman’s cervix.
o Artificial insemination by a donor: If man is infertile, a donor may be
matched with prospective father for physical characteristics.
o Ovum transfer: A donor egg is fertilized in lab and transferred to mother’s
uterus.
o Donor egg: When a woman is producing poor quality ova or has had her
ovaries removed.
o Blastocyst transfer: Fertilized ovum is kept in culture until the develops into
a blastocyst and then implanted into mother’s uterus.
o Gamete intrafallopian transfer(GIFT) and Zygote intrafollopian transfer
(ZIFT): Egg and sperm or fertilized egg is inserted into the fallopian tube.
o Surrogate motherhood: A fertile woman is impregnated by the prospective
father and agrees to give the baby to the couple.
II. Mechanisms of Heredity
 Heredity: Inborn factors which are inherited from the biological parents that affect
development.
A. The Genetic Code
 Deoxyribonucleic acid (DNA): Chemical that carries inherited instructions
for the formation and function of body cells.
 Bases: Chemical units which make up DNA (A, T, C, G) and form pairs.
o adenine + thymie
o cytosine + guanine
 The Genetic Code: Sequence of base parts within DNA that determine
inherited characteristics.
 Chromosomes: Coils of DNA that carry genes.
 Genes: Small segments of DNA located in definite positions on particular
chromosomes.
 Meiosis: Complex process of cell division in which each gamete (sperm or
ovum) ends up with only 23 chromosomes-one from each pair.
 Monomorphic genes: The three quarters of the genes every child receives that
are identical to the genes that every other child receives.
 Polymorphic genes: The other quarter of the genes which define each child as
an individual.
 Mitosis: Process by which cells divide in half over and over again duplicating
themselves.
B. What Determines Sex?
 Autosomes: 22 pairs of chromosomes not related to sexual expression.
 Sex chromosomes: Pair of chromosomes that determine sex: XX in the
normal female, XY in the normal male.
 SRY gene: Gene for maleness.
 Wnt-4 molecule: Controls femaleness.
C. Patterns of Genetic Transmission
1. Dominant and Recessive Inheritance
 Alleles: Paired genes (alike or different) that produce alternative
expressions of a characteristic.
 Homozygous: Possessing two identical alleles for a trait.
 Heterozygous: Possessing different alleles for a trait.
 Dominant inheritance: Pattern of inheritance in which, when a child
recieves contradictory alleles, only the dominant one is expressed.
 Recessive inheritance: Pattern of inheritance in which a child recieves
identical recessive alleles resulting in expression of a nondominant trait.
 Polygenic Inheritance : Interaction of several genes.
 Mutations : Permanant alterations in genetic materials.
 Epigenesis: Mechanism that turns genes on or off and determines
functions in the body.
2. Genotypes and Phenotypes: Multifactorial Transmission
 Phenotype: Observable characteristics of a person.
 Genotype: Genetic makeup of a person, containing both expressed and
unexpressed characteristics.
D. Genetic and Chromosomal Abnormalities
1. Dominant or Recessive Inheritance of Defects
 Incomplete Dominance: A trait that is not fully expressed.
2. Sex-Linked Inheritance of Defects
 Sex-linked inheritance: Pattern of inheritance in which certain
characteristics carried on the X chromosome inherited from the mother are
transmitted differently to her male and female offspring.
 Carrier: Parent does not have the disorder but can pass it on to children.
3. Genome Imprinting
 Genome imprinting: Differential expression of genetic traits depending on
whether the trait has been inherited from the mother or the father.
4. Chromosomal Abnormalities
 Down syndrome: Chromosomal disorder characterized by moderate to
severe mental retardation and a downward sloping skin fold at the inner
corners of the eyes. Also called trisomy-21.
E. Genetic Counseling and Testing
 Genetic counseling: Clinical service helps prospective parents assess their
probable risk of having children with genetic or chromosomal defects.
 Karyotype: A chart of chromosomes sorted according to size and structure.
III. Nature and Nurture: Influences of Heredity and Environment
A. Studying the Relative Influences of Heredity and Environment
 Behavioral genetics: Quantitative study of how much heredity and environment
influence particular traits.
1. Measuring Heritability
 Heritability: Statistical estimate of how great a contribution heredity makes to
individual differences in a specific trait at a certain time within a given
population.
 Family studies: Measure the degree to which biological relatives share certain
traits and whether the closeness of the family relationship is associated with
the degree of similarity.
 Adoption studies: Look at similarities between adopted children and their
adoptive families and also between adopted children and their biological
families.
 Studies of twins: Compare pairs of monozygotic twins and same-sex
dizygotic twins.
 Concordant: Term describing a statistical tendency to show the same trait.
B. How Heredity and Environment Work Together
 Developmental System: A combination of constitutional, social, economic and
cultural factors that shape development.
1. Reaction Range and Canalization
 Reaction range: Range of potential expressions of an inherited trait.
 Canalization: Limitation on variance of expression of certain inherited
characteristics.
2. Genotype-Environment Interaction
 Genotype-environment interaction: Effects of similar environmental
conditions on genetically different individuals.
3. Genotype-Environment Correlation
 Genotype-environmental correlation: Tendency of certain genetic and
environmental influences to act in the same direction; may be passive, reactive
(evocative) or active.
o Passive correlations: Parents, who are genetically related to the child,
provide the rearing environment for the child. Child does not control
environment.
o Reactive, or evocative, correlations: Child’s genotype elicits certain types
of physical and social environments.
o Active correlations: Children seek out environments that they find
companionable and stimulating.
 Niche-picking: Tendency of a person, especially after early childhood, to
seek out environments compatible with his or her genotype.
4. What Makes Siblings So Different? The Nonshared Environment
 Nonshared environmental effects: The unique environment in which each
child grows up, consisting of distinctive influences or influences that affect
one child differently than another.
C. Some Characteristics Influenced by Heredity and Environment.
1. Physical and Physiological Traits
 Obesity: Extremely overweight in relation to age, sex, height, and body type;
sometimes defined as having a body mass index (weight-to-height) at or above the
85th or 95th percentile of growth curves for children of the same age and sex.
2. Intelligence
 Heritability estimates: 50 to 60 percent for verbal abilities and 50 percent for
spatial abilities.
3. Personality
 Temperament: A person’s characteristic style of approaching and reacting to
situations.
 Heritability estimates: On 5 major aspects of traits, 40 percent: on scales
without measurement errors, 66 percent.
4. Psychopathology
 Schizophrenia: Mental disorder marked by loss of contact with reality;
symptoms include hallucinations and delusions. May originate in a lack of a
chemical called reelin.
 Autism: Pervasive developmental disorder of the brain, characterized by the
lack of normal social interactions, impaired communication and imagination,
and repetitive, obsessive behaviors.