The Developing Person Through the Life Span 8e

by Kathleen Stassen Berger

Chapter 3 Heredity & Environment

The Genetic CodeEpigeneticsGene-Gene InteractionsChromosomal & Genetic Problems

The Genetic Code

GeneSmall section of a chromosome, the basic

unit for transmission of heredity.Consists of a string of chemicals that

provide instructions for the cell to manufacture certain proteins

The Genetic Code

Chromosomes:Molecules of DNADNA consists of 46

chromosomes arranged in 23 pairsGenome:The full set of genes that

are the instructions to make an individual member of a specific species

The Beginnings of Life

Gametes• Reproductive cells (sperm and ova)• Each consists of 23 chromosomes.

Zygote

Two gametes (sperm and ovum) combine and produce a new individual with 23 chromosomes from each parent.

Genotype vs Phenotype

Genes are passed down from generation to generation

Genotype• An organism’s genetic

inheritance, or genetic potential

• Unique for each organism

PhenotypeObservable characteristics, including appearance, personality, intelligence, and all other traits.

The Beginnings of Life

The zygote begins duplication and division then differentiation and specialization occur.

Cells change from being stem cells, those from which any other specialized type of cell can form, to being only one kind of cell.

Twins

Monozygotic (identical) twins

Originate from one zygote that

splits very early in development

Same genotype

Dizygotic (fraternal) twins Result from fertilization of two separate ovaby two separate spermIncidence is genetic and varies by ethnicity and age

Chapter 4 – Prenatal Development and

Birth

The Developing Person Through the Life Span 8e

by Kathleen Stassen Berger

Prenatal Growth

Three main periods of prenatal development1. Germinal Period (1st two weeks after

conception): rapid cell division and beginning of cell differentiation

2. Embryonic Period (3rd through 8th week): basic forms of all body structures develop

3. Fetal Period (9th week until birth): fetus grows in size and matures in functioning

The Germinal Period

Zygote begins duplication and division within hours of conception

Development of the placenta Organ that surrounds the developing embryo Sustains life via the umbilical chord

Implantation (about 10 days after conception) Developing organism burrows into the placenta that

lines the uterus

The Embryonic Period

Embryo 3rd through the 8th week after conception Begins when the primitive streak appears down the

middle of the cell mass Primitive streak becomes the neural tube and later

the brain and spinal column Eyes, ears, nose, and mouth form Heart begins to pulsate Extremities develop and webbed fingers and toes

separate

The Fetal Period

Fetus9th week after conception until birthGrowth periodHeartbeat detectable via stethoscopeCortex is not fully mature at birthBrain at birth is biggest part of baby

Age of Viability

Age of Viability Age at which a preterm

newborn may survive outside the womb with medical care

About 22 weeks after conception

Brain is able to regulate basic body functions

Chances of survival increase with each day after the 22-week mark

Who is likely to have a preterm birth?Best predictor is a previous preterm deliveryFamily HistoryMultiple Births (twins or more)Women with uterine or cervical abnormalities

Preterm Births

Medical Factors Increasing the Likelihood of a Preterm Birth

• Diabetes• High Blood Pressure• Clotting Disorders• Birth defects in baby• Mother overweight/very

underweight• Short time between pregnancies

Preterm Births

Lifestyle Factors Increasing the Likelihood of a Preterm Birth

• Lack of Social Support• Late/No Prenatal Care• Domestic Violence• Smoking During

Pregnancy• Drinking Alcohol/Drugs• StressResearch suggest low socioeconomic status

and lower education level are significantly related to preterm births

Low Birthweight

Low Birthweight (LBW) less than 5 ½ lbs.

Very Low birthweight (VLB)less than 3 lbs 5 ounces

Extremely Low Birthweight (ELB)less than 2 lbs 3 ounces

Consequences of Low Birthweight:•Cognitive Difficulties•Delayed pre-linguistic and linguistic development•Visual and hearing impairments•Attention Difficulties•Behavioral Difficulties•Higher rates of obesity, heart disease, and diabetes

Birth

Apgar scale Quick assessment of newborn’s heart rate,

breathing, muscle tone, color, and reflexes Completed twice (1 minute and 5 minutes after

birth) Score of 0, 1, or 2 in each category Desired score: 7 (total) or above

Harmful Substances

Teratogens Substances and conditions that can impair

prenatal development and result in birth defects or even death

Behavioral Teratogens Affect the child’s developing brain

Developmental retardation, hyperactivity, and learning disabilities

Effects do not become evident for months or years

Birth Defects from Teratogens

Applying the Research

Fetal alcohol syndrome (FAS) A cluster of birth

defects including abnormal facial characteristics, slow physical growth, and retarded mental development

May occur in the child of a woman who drinks alcohol while pregnant

Moving and Perceiving

The first movements are not skills but reflexes, involuntary responses to a particular stimulus.

Brazelton Neonatal Behavioral Assessment Scale (NBAS) A test that measures responsiveness Records 46 behaviors, including 20 reflexes

Infant Reflexes

breathing, thrashing, sucking, rooting, swallowing, spitting up

Reflexes Signal Normal Functioning

Babinski reflex When feet are stroked, their toes fan upward.

Stepping reflex When held upright with feet touching a flat surface, infants move their legs as if to walk.

Swimming reflex When laid horizontally on their stomachs, infants stretch out their arms and legs.

Palmar grasping reflex When something touches infants’ palms, they grip it tightly.

Moro reflex When someone startles them, infants fling their arms

outward and then bring them together on their chests, as if to hold onto something, while crying with wide-

open eyes.

Reflexes aid survival