Biological and Environmental Factors

Chapter 2 Summary Notes

* Notes for educational purposes only-use with course textbook

Overview

Bases for Genetic make-up

Choices in Reproduction

Development and the Family

The Relationship Between Heredity and Environment

Genetics

Heredity and environment are foundations of development

Genotype- genetic make-up

Phenotype- observable characteristics

Genetic Code

Body composed of over a trillion cells

Center of cell is nucleus which contains chromosomes

Chromosomes- store and transmit genetic information

DNA- double strain molecules that makeup chromosomes and contain genetic code

Gene- segment of DNA molecule

Mitosis- cell duplication (each cell receives exact copy of genetic code)

Sex Cells

Gametes-sex cells (sperm 23 chromosomes and ovum 23 chromosomes)

Meiosis- cell division that forms gametes No two gametes will ever be the same Zygote- sperm and ovum unite at conception 46

Chromosomes Sperm are produced continuously; all ova are

present at birth 22 autosomes; 1 sex chromosome; xy- male; xx-

female

Mulitiple Births

Twins– Fraternal (dizygotic) most common type

• Two ova are fertilized; genetic makeup similar to ordinary siblings

– Identical (monozygotic) one zygote separates into two clusters of cells that become two individuals; same genetic makeup

Triplets (3); Quadurplets (4); Quintuplets (5); Sextuplets (6), Septuplets (7)

Increase in Multiple Births?!

Increase Facts

1978-1988- 17% single births; 33% twin births; 101% triplets and higher

Trends in family planning and advances in reproductive technology assist in increase

Patterns of Genetic Inheritance

2 forms of genes occur at the same place on the autosome- father & mother

Homozygous- alike genes from both parents (inherited trait)

Heterozygous- different genes from both parents- relationship of genes determine trait that will appear.

Dominant- recessive inheritance- a pattern one gene’s influence is exhibited (heterozygous)

Dominant- Recessive Terms

Dominant- expressed gene

Recessive- not expressed

Carrier- heterzygous; pass recessive gene to his/her children

Diseases that are result of recessive genes PKU Cystic Fibrosis Sickle Cell Anemia Tay-Sachs disease Hemophilia

(Page 50 in text)

Who is more at risk ( Multiple Births)? Older women Women with more children Fertility drug clients African American Women (fraternal

twins) Tall, normal, or overweight (fraternal

twins)

Patterns of Genetic Inheritance

2 forms of each gene occur at the same place on the autosomes- 1 mother; 1 father

Homozygous- both genes are alike

Heterozygous- relationship between genes determine trait that will appear

Dominant- Recessive Inheritance

A pattern in a heterozygous relationship only one gene’s influence is exhibited

Dominant- expressed

Recessive- not expressed

Carrier- heterozygous relationship passes recessive gene

Diseases with recessive trait

PKU Sickle Cell Anemia Tay-Sachs Disease Cystic Fibrosis Cooley’s Anemia

(Pages 50-51 in text) Genetically linked

illnesses

Codominance

Codominance– Both genes influence the person’s

charateristics– Sickle Cell Anemia

Mutation

Change in DNA segment Harmful genes By chance Or by hazardous substances in the

environment

X-linked inheritance- recessive gene is carried on the X-Chromosome– Males more likely to be affected (sex

chromosomes don’t match)– Hemophilia

Males may be at a disadvantage in other areas not necessary linked to X-linked inheritance- miscarriage and infant deaths

Learning disability, behavior disorders mental retardation (Halpern, 1997)

Genetic Imprinting

Pattern of inheritance where some genes are chemically marked in such a way that one pair is activated regardless of its makeup– Diabetes in the father – Asthma in the mother– Fragile X syndrome (MR, autism) mother

Chromosomal Abnormalities

Defect occurs during meiosis (DNA) Down Syndrome

– 21st chromosome contains extra genetic material– Physical features- short, stocky build, flatten face,

protruding tongue, almond shape eyes, possible heart and intestinal defects, speech problems, delayed motor and cognitive defects

– Increase chances of having a baby with Down Syndrome with age of mother

Abnormalities in Sex Chromosomes Either the presence of extra chromosome or

the lack of one of the X chromosomes Triple X syndrome (XXX)- girl- verbal

difficulties Turner syndrome- (XO) missing X-spatial

relationships Klinefelter syndrome (XXY)- verbal difficulties

Reproductive Choices

Genetic Counseling- communication about chances of couples having a baby with hereditary disorders

Prenatal diagnostic methods– Page 55 in text

Other choices

Adoption In vitro fertilization Fertility drugs

Environmental Factors

Family Friends School Experiences Society Culture

Social Systems Perspective

Family as complex system– Behavior of family affects those of other family

members Influence is directed or indirect- third party

can support or undermine other family relationships

Family dynamic ever- changing system Can be modified by important life events Development status of each family member

and historical time period effects families

Socioeconomic Status (SES) and Family Functioning 3 variables

– Years of education– Job prestige and skills required– Income– SES may affect differences in child-rearing practices– Lower- SES family may focus on external

characteristics (obedience, neatness, cleanliness)– Higher SES focus on psychological traits-curiosity

• Happiness, and self- direction• As early as 2nd year of life SES affects with cognitive and

language development

Impact of Poverty

36 million people 14% of the population Hardest hit

– Parents under 25 with young children– Elderly who live alone– Ethnic minorities– Women– 20% children; 32% Hispanic; 40% African

American; 32% Native American

More on Poverty

Parents in poverty– Experience hassles and crises affecting child-

rearing ability– Poor housing and dangerous neighborhoods

increase stress levels of poor families– Homeless children suffer from developmental

delays, emotional stress, health problems, school absenteeism, poor academic performance

Beyond the Family

Community impact on family– Child abuse and neglect are greatest

• With weak family and community ties• Family stress and child adjustment problems are

reduced with strong family ties• Safe neighborhoods and communities with physical and

social support• Influence well-being in adulthood• Smaller towns- fewer culture experiences than cities-

greater community involvement and safer environments

Culture

Cultures shape family interactions and community settings beyond the home

American cultural values- independence – Self-reliance, privacy– Subcultures- groups of people with beliefs

and customs that differ from those of the larger culture

African American Extended Family Extended family- 3 or more generations live

together Survival poverty, prejudice and economic

deprivation (McAdoo) More kin visits Reduce stress Grandmothers are significant Elderly have higher life satisfaction Strong Family bonds, child development Survival for future generations

Individualism vs. Collectivism

Individualism societies- people think of themselves as separate entities; concerned with their own goals (US)

Collectivism societies- people define themselves as part of a group and stress group over individual goals