HEREDITY AND ENVIRONMENT Chapter 2

Heredity and Environment

DNA is a complex molecule made up of nucleotides and four different bases Bases form base pairs that should not vary Basic units of inheritance are genes- delineated pieces of DNA There are about 25,000 genes in human body Molecular Genetics

Major Features of a Typical Cell

Note the twisted ladder-like structure, referred to as a double helix. Base pairs form the rungs on the DNA ladder, (here in blue and purple), and their sequence determines the genetic traits that are carried in the DNA of each individual. Computer-Generated Stimulation of DNA Molecule

Segment of DNA Visualized as Ladder

How Can Such a Simple System Dictate How Life Unfolds? Number of base pairs in DNA molecule are very large Different species, and even different individuals within the same species, have different numbers of base pairs in their genome Order of pairing is important According to the Human Genome Project, all humans are 99.9% genetically identical.

Protein synthesis Most significant thing genes do is build proteins Proteins are molecules that control life Over 200,000 different proteins have been identified in humans What Is Protein Synthesis?

Common Proteins and Their Functions in the Human Body

When cell divides, DNA assembles into chromosomes Chromosomes are chains of genes that can be observed directly All cells except sperm and egg cells contain 23 pairs of chromosomes First 22 of those pairs are matching, and are referred to as autosomes The 23rd pair determines sex selection and is labeled XX in females and XY in males One’s chromosomal makeup can be visualized in karyotypes Genes, Chromosomes, and Cell Division

Human Karyotypes

Cell Division and Reproduction

Comparison of Mitosis and Meiosis

All of person’s pairs of alleles that form their genetic code Dominant allele Recessive allele Dominant trait expression Recessive trait expression Genotype From Genotype to Phenotype

Simple dominance and recessive When an allele is dominant, its presence in gene pair has tendency to cause that trait to be expressed characteristic or trait Homozygous Heterozygous Combination of genes Combinations of many gene pairs determine most traits Polygenetic inheritance

Examples of Dominant-Recessive Gene Combinations

Determined by more than one gene pair Polygenic human characteristics Usually passed on by X chromosome Sex-linked traits Hypothetically, the same parents can produce hundreds of trillions of unique children. Genetic Inheritance

May occur during mitosis or meiosis when DNA molecule is altered during cell division May be beneficial or detrimental Genetic mutation s Genetic Inheritance

Genetic anomalies Involve problems with instructional mechanism of genetic process Sex-linked disorders Can occur when gametes do not replicate correctly or when genetic information, even entire chromosomes, are missing or duplicated Genetic and Chromosomal Disorders

Crossing Over of Chromosomes Sometimes during meiosis parts of chromosomes cross over, which creates new combinations of genes on a chromosome. Source: Derived from Life (4th ed.), by R. Lewis, D. Gaffin, M. Hoefnagels, and B. Parker, 2002, New York: McGraw-Hill.

Gene-Environment Interactions: The Study of Epigenetics Individuals differ not only in their genes, but also in specific ways in which they experience their environments Environmental forces can change gene expressions Gene-environment interactions occur at many levels Experience in life can have dramatic effect on later developmental outcomes Epigenetic modifications may be transmitted to next generation via genetic inheritance

Some Sex-Linked Disorders

Autosomal Disorders

Genetic research Uses recombinant DNA technology to reconstruct cells and genes Gene therapies Involve reinserting genetically- altered cells into a person In vivo gene therapy Removes some viral genes, inserts cloned normal genes and reintroduces retrovirus to patient Genetic Research

Description of different types of genetic testing: Video Clip

BBC documentary on Designer Babies with commentary by Princeton professor Lee Silver: feature=PlayList&p=C7E239A945F4C4BA&playne xt=1&playnext_from=PL&index=56 Video Clip

Behavior genetics Tries to understand the genetic origins of behaviors Incorporates the view that complex traits are determined by interaction of heredity and environment Looks at statistical correlation, or concordance, of similar characteristics with genes What is a concordance rate? Let’s find out. Behavior Genetics

Concordance rates form the basis of estimates of heritability, the proportion of a trait that is thought to result from genetic factors. How are these estimates determined? Behavior Genetics

Behavior Genetics Studies

Basic Processes that Affect Behavior Habituation Classical Conditioning Operant Conditioning Social Learning Environmental Influences and Contexts

A Typical Classical Conditioning Procedure

Operant Conditioning Reinforcers increase the likelihood that a behavior will be repeated Punishments decrease the probability that a behavior will be repeated

Applied Behavior Analysis Application of learning principles to change behavior Sometimes called behavior modification Applied behavior analysis

Family systems are at heart of human behavior Families pay critical role in orienting people to society and culture Siblings share many similar experiences, but non- shared experiences and relationships also exist Family and Culture

Stop and Think! Your textbook suggests it is important to avoid ethnocentrism. Do you agree? Why? Why not?

Cultural factors affect a cohort, a group of individuals born during the same historical era. How would you describe YOUR cohort? Sociocultural Influences

Types of cultural influences Normative age-graded: biological and social changes Normative history-graded: historical events such as wars, depressions, and epidemics Non-normative: individual factors such as divorce, unemployment, illness, career changes Sociocultural Influences

A Lifespan Profile on Influences

Development in a Broad Context