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 transmittedMyers: Psychology, Eighth EditionCopyright © 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.

The Collaborative Gene

Genetic Foundations

• 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

Cells, Chromosomes, Genes, and DNA

Genetic Foundations

Fig. 2.3

Nucleus (center of cell) contains

chromosomes and genes 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

b bB bB bB B

b

B

Blond hair

Brown hair

How brown-haired parents

can have a blond-haired

child: the gene for blond hair is

recessiveMother

B bFather

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 developmentMyers: Psychology, Eighth EditionCopyright © 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)

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

Prenatal Development

Fig. 2.10

Teratogens and Timing of Their Effects on Prenatal Development

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, impulsivity- impacts 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

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

Birth

Fig. 2.11

The Apgar Scale

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

Birth

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