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Chapter 3
Forming a New Life
• Fertilization: conception, sperm meet
ovum.
• Zygote: single cell union of sperm and
ovum
• Girls: 2 million immature ovum in two
ovaries at birth. Every 28 days is swept
along fallopian tube by tiny cilia, toward the
uterus or womb. Fertilization usually occurs
during the 2-3 days when the ovum is
passing through the fallopian tube.
• Boys: sperm produced by testicles at a rate
of about several hundred million per day
and are ejaculated in the semen at orgasm.
Sperm attempt to swim though cervix
(opening of the uterus) and into fallopian
tubes, but only a few make it. Pregnancy
can occur up to five days after sperm enters
vagina.
Figure 4.1 Life is sexually transmitted
Myers: Psychology, Eighth Edition
Copyright © 2007 by Worth Publishers
Multiple births
• Dizygotic twins (fraternal twins):
unfertilized egg splits and both are fertilized
• Monozygotic twins (identical twins): single
fertilized ovum splits into two.
Temperament may differ, but most
everything else the same.
Two Types of Multiple Births
• Monozygotic (MZ)
 One egg – One sperm
 Identical Twins
 Share 100% of genes
• Dizygotic (DZ)




Two eggs – Two sperm
More common
Fraternal Twins
Share 50% of genes – just like non-twin siblings
Determination of Sex
Sex Determination
• Chromosomes: Coils of DNA carrying genes
 Autosomes:
 22 pairs not related to sexual expression
 Sex chromosomes:
 1 pair determining sex
 XX = female
 XY = male
DNA: deoxyribonucleic acid: double-helix
containing genetic code.
Chromosomes are coils of DNA that contain
segments called genes (units of heredity)
23 pairs of chromosomes from each parent.
Each sex cell ends up with 23 chromosomes
(meiosis)
though mitosis, the nonsex cells continue to
divide and replicate so that every cell has
same DNA.
Genetic Foundations
The Collaborative Gene
• Genes and chromosomes
– Mitosis — cell nucleus duplicates
– Meiosis — cell division forms gametes
– Fertilization — egg and sperm form zygote
– Genetic variability in the population
– X and Y chromosomes determine sex
Genetic Foundations
Cells, Chromosomes, Genes, and DNA
Nucleus (center of
cell) contains
chromosomes
and genes
Fig. 2.3
Chromosomes are
threadlike structures
composed of DNA
molecules
Gene: a segment of DNA
(spiraled double chain)
containing the hereditary
code
• 22 pairs of chromosomes are not related to sex
(autosomes).
• The 23rd pair are sex chromosomes: all ovum
chromosomes are x, but sperm may have the x or y
chromosome. The y is for males (XY) and the x
for females (XX).
• Dominant inheritance: when heterozygous,
dominant trait governs.
• Recessive inheritance: expression of a recessive
trait, occurs when received two recessive alleles,
one from each parent.
• Polygenetic inheritance: pattern of
inheritance in which multiple genes at
different sites on chromosomes affect a
complex trait
•
• Multifactorial transmission: comb of
genetics and environmental factors produce
certain complex traits
•
• Phenotype: observable characteristics of a
person
• one from each parent.
Genetic Foundations
How brownhaired parents
can have a
blond-haired
child: the gene
for blond hair is
recessive
B Brown
hair
Blond
b hair
Father
Bb
B B
B b
Mother
Bb
B b
b b
• Genotype: genetic make-up of a person,
containing both expressed and unexpressed
characteristics
• Defects: both parents give recessive gene
for the abnormality; also if dominant
parent’s DNA has it
• Mutations: spontaneous or environmentally
induced
• Genotype: genetic make-up of a person,
containing both expressed and unexpressed
characteristics
• Defects: both parents give recessive gene for the
abnormality; also if dominant parent’s DNA has it
• Mutations: spontaneous or environmentally
induced
Problems
• Genetic and environmental causes; if has genetic
marker, environment may trigger. May also trigger
without environment. (traits, personality,
intellectual, obesity, diabetes)
• Fertilization to two weeks: germinal stage,
zygote divides and becomes complex,
implanted into uterus wall- formally
beginning pregnancy.
• (see pages 86-87 for development stages)
Figure 4.2 Prenatal development
Myers: Psychology, Eighth Edition
Copyright © 2007 by Worth Publishers
Stages of Prenatal Development
Stage
Duration
Germinal
Conception to 2 weeks
Embryonic
2 to 8 weeks
Fetal
8 weeks to birth
Germinal Stage Development
Embryonic stage (2-8 weeks)
• Major bodily systems develop
• Spontaneous abortion: usually due to
chromosomal abnormalities, severely
defective embryos. Occurs usually without
mother aware (50% end in miscarriage;
15% known to mother)
Fetal Stage (8-birth)
• Appearance of bone cells; rapid growth;
more complex organ development; begin to
interact with environment; learn and
remember (sound, voices)
Prenatal Development
Hazards to Prenatal Development
• Teratogen: agent causing birth defects
• Severity of damage affected by
– Dose
– Genetic susceptibility
– Time of exposure
• Effects of prescription and nonprescription
drugs
Prenatal Development
Teratogens and Timing of Their Effects on
Prenatal Development
Fig. 2.10
Teratogen: is a substance that can cross the
placental barrier and harm the child. Alcohol
and tobacco are perhaps the most common and
damaging. Mercury, landfills, lead paint
Fetal Alcohol Syndrome (FAS): combo of retarded
growth, face and body malformations,
disorders of the nervous system. ADHD
symptoms, attention, distractibility, learning
difficulties, memory and mood impairment.
Nicotine: low birth weight, miscarriage,
retardation, still birth, small head syndrome,
medical problems.
Marijuana: birth defects, low birth weight,
ADHD, learning problems, visual and
perceptual skills deficit, impulsivityimpacts frontal lobe.
Cocaine: spontaneous abortion, delayed
growth, premature labor. Low birth weight,
birth defects, neurological deficits; acute
withdrawal following birth; overall,
significant neurological deficits.
HIV/AIDS: likely to spread it to fetus.
Maternal Illnesses: colds, STDs, general
medical problems.
Maternal Stress: wide psychological
disorders, deformities. Negative
emotional/behavioral
Over 35: for the mother-diabetes, high BP,
severe bleeding. Child- premature birth,
birth defects, retarded growth.
Physical Development—
Hazards to Prenatal Development
28
Birth
Assessing the Newborn
• Apgar Scale: heart, reflexes, and color
• Brazelton Neonatal Behavioral Assessment
Scale (BNBAS)
– A sensitive index of neurological competence
– Four categories in global terms
• Neonatal Intensive Care Unit Network
Neurobehavioral Scale (NNNS)
– Analysis of behavior, neurological and stress
responses, and regulatory capacities
Birth
The Apgar Scale
Fig. 2.11
Birth
Bonding
• Needs to occur shortly after birth
• Early emotional attachments may create
healthy interactions after leaving hospital
• Rooming-in arrangements offered
• Massages and tactile stimulation for
premature infants affect development
Recommended now: Comfort your baby:
• comfort baby when they cry
• feed them when they are hungry
• play with them when they are awake
• “spoil” them as much as you can! (studies
show that baby must learn that they have an
effect on their environment, and therefore
control over their own experience. Important
for cognitive and social development
• babies need to know that they can make
things happen
• being responsive to baby