DEVELOPMENTAL PSYCHOLOGY

Week 2:

Foundations of Development

DEVELOPMENTAL PSYCHOLOGY

Influences on development

Genetic foundations

Environmental context

Genetic foundations of development Genetic code conveyed in deoxyribonucleic acid (DNA)

Gene: segment of DNA along length of chromosome

Allele: viable DNA (deoxyribonucleic acid) coding that occupies a given locus (position) on a chromosome.

DNALadder-like molecule, formed of chains of

nucleotide subunits. - deoxyribose sugar- a phosphate- a base. A set of three bases – a codon – acts as a

blueprint for the incorporation of a particular amino acid, the subunit of a protein molecule.

The two halves are joined together by the bases – a purine (adenine or guanine) or pyrimidine (cytosine or thymine) – forming pairs (the rungs of the ladder).

The bases form into two specific base pairs: adenine with thymine and guanine with cytosine.

National Human Genome Research Institute (NHGRI) http://www.genome.gov/12514471 by artist Darryl Leja

Genes

Length of a gene varies greatly

Gene concordance between human and chimpanzee is high (98% - 99%)

Only one base pair change is enough to influence human traits and capacities

Beginning of life

Gametes have 23 chromosomes

Combination of two gametes → zygote

Cell division (meiosis) – exchange of material causing variation

TwinsMonozygote- Identical- 100% concordance - 1 / 285

Dizygote- Non-identical, Fraternal

- 50% concordance

Patterns of genetic inheritance

An organism in which the two copies of the gene are identical — that is, have the same allele — is called homozygous for that gene.

An organism which has two different alleles of the gene is called heterozygous.

Class Activity

Dominance / recessive inheritance

Phenotypes: the expressed characteristics

Dominant characteristic: when only one allele affects the expression

Recessive characteristic: needs two alleles of the same type before it is expressed

Allele

Father/Mother

B b

B BB

(dom)

Bb(carrier)

b Bb(carrier)

bb

(rec)

Importance of genetic inheritance Understanding of how we express physical characteristicsUnderstanding of how some diseases/defects are

transmittede.g. PKU, an inability to metabolise amino acid

phenylalanine, causing CNS damage in first year of life, is a recessive code, that strikes 1 / 8k births. Both parents must have recessive allele for child to get PKU

Incomplete dominance

Cases where the pattern of inheritance in which both alleles are expressed, resulting in a combined trait or one that is intermediate between the two

For example, red flower and blue flower, after cross pollination, we get purple flowers

X-linked inheritance

In cases where the harmful allele is carried on the X chromosome, there is greater chance of the male expressing the disorder due to the fact that males only have one X chromosome

Usually is passed on by mother to sonHemophilia, muscular dystrophy, adrenoleukodystrophy, green colourblindness, fragile-x syndrome

Genetic imprinting

This refers to the chemical marking of a particular allele, such that the trait is always expressed

Genetic imprinting is a vaguely similar to monosomy but with different sequelae.

Genetic imprinting is the process by which certain mammalian genes are switched off during early embryo development, according to whether they were inherited from the father or mother.

Mutation

Sudden changes in the DNA which may affect one, two, or many genes. Such mutations could occur spontaneously or as by-product of harmful environmental agent (tetragenic)

Chromosomal abnormalities

Abnormalities within the chromosomes – give rise to developmental problems

Down syndrome: consequences include MR, memory and speech problems, slow motor development

Sex chromosome abnormalities: XYY syndrome, Klinefelter syndrome, Turner Syndrome

Class Discussion• Referring to ecological systems theory, explain why

parents of children with genetic disorders often experience increased stress. What factors, within and beyond the family, can help these parents support their children’s development?

Genetic counselling

Process by which to help ensure healthy babies

Maternal age, family background

Prenatal Diagnostic Methods

Method Description Timing

Amniocentesis Obtaining sample of uterine fluid by drawing fluid with syringe through abdominal wall

11-15weeks

Chronic Villus sampling

Removal of plug of tissue for analysis, entry via vagina

6-8weeks

Fetoscopy Visual analysis of the fetus, possible to obtain blood sample

5-18weeks

Ultrasound Beaming of high frequency sound waves at uterus

Caution <5x

Maternal blood analysis

Testing for elevated level of alpha-fetoprotein

By 2nd month

Preimplantation genetic diagnosis

Associated with in vitro fertilisation and duplication of zygote

Advantages of GC

Improving chances of healthy babies

Better prepared for what may come to pass

Prenatal diagnosis has led to advances in fetal medicine – administration of drugs, surgery, blood transfusions for fetus.

Environmental context for development (1)Family – having family support gives potential for social interaction

Direct influence: parents, grandparents

Indirect influence: third party effects such as emotional influences

Environmental context for development (2)Socioeconomic status – affects duration and timing of phases of family life cycle

- Early Vs late marriage- Number of children- Family interactions

Environmental context for development (3)Affluence and poverty

Collectivist Vs individualistic societies

Legal system and society support

Policies for the family

MCDYS- Promoting marriages- Supporting families- Nurturing and protecting the young

National family week – “eat with your family day”

Relationship between hereditary and environmentHereditary estimate: extent to which individual differences in complex traits in a specific population are due to genetic factors

Kinship studies compare characteristics of family members

Concordance rate: refers to the percentage of instances in which both twins show a trait when it is present in one twin

LifeSpan Development

Name the times in life that come to your mind

What is lifespan development?

When does lifespan development start?

Life Span Perspective

Leading dynamic systems approach- Lifelong - Multidimensional and multidirectional- Highly plastic- Affected by multiple interacting forces

27

Stages in development

Conception Embryonic developmentFetal developmentInfant ToddlerChildhoodAdolescenceYoung adulthoodMiddle adulthoodLate adulthood

Conception / Germinal stageConception occurs when a sperm joins with an egg

When fertilisation has occurred, the newly formed zygote will make its way down to the womb

By the end of a week, the blastocyst will implant in the uterine lining

Period of Zygote

First two weeks, within first trimester

Single cell zygote will multiply and form blastocyst

Embryonic period

3 – 8 weeks (first trimester)

Many major organs developed e.g. CNS, heart, muscles, ribs, backbone, digestive track, arms, legs, feet, toes, fingers

Period of the Fetus

This is the time of physical growth

Organs now get connected

New behaviours are learned

9 – 12 weeks – still within first trimester, lasts until birth of the infant

Teratogens

Any environmental agent that causes damage during the prenatal period

Effect is dependent on a few factors- Age- Dose- Heredity- Other negative influences

TeratogensSubstances that can produce birth defects

Especially harmful during embryonic period

E.g., Alcohol Use may cause Fetal Alcohol Syndrome (leading cause of preventable Mental Retardation)

-- Smoking during pregnancy restricts oxygen to the unborn: greater risks for several problems

Effect of teratogens (1)Prescriptive and OTC Drugs: for

relief from simple ailments – asprin, anti-depressants, caffeine – far reaching consequences

Illegal drugs: often consumed as a way of escaping reality – LT potential –ve effect

Tobacco: first, second and even third hand, has effect on reducing birth weight

Alcohol: fetal OH syndrome, effects

Radiation: possibility of physical defects, LBW, miscarriage, etc.

Environmental pollution: increased chance of life threatening diseases and future health problems

Infectious diseases: possible correlation with cataracts, deafness, heart, genital, urinary and intestinal abnormalities, and even MR

Effect of teratogens (2)

Effect of Maternal Factors

Maternal nutrition

Emotional stress

Rh factor incompatibility

Maternal age and previous birth experience

Group Discussion

• If you had to choose five environmental influences to publicize in a campaign aimed at promoting healthy prenatal development, which ones would you choose, and why?

Stages of Childbirth

Dilation and effacement of the cervix (12 – 14 hours 1st birth) to Transition

Delivery of the baby (pushing and birth)

Delivery of the placenta

Developmental scales

Apgar scales: measures physical condition- Five different scales: Appearance (colour), Pulse (heartrate), Grimace (reflex/irritability), Activity (muscle tone), Respiration (breathing)

- Score 0, 1, 2

New-born Baby’s CapacitiesNewborn Reflexes- Eye blink- Rooting- Sucking- Moro- Palmer grasp- Tonic neck- Stepping- Babinski

New-born states: Arousal

Infant States of Arousal

Regular sleep

Irregular sleepQuiet alertness

DrowsinessWaking actively and crying

New-born states: Senses

Touch – highly sensitive to pain

Taste – able to distinguish basic tastes

Smell – shows distinct preference

Hearing – preference for complex tones

Vision – least developed in the newborn