Chapter 2 HEREDITY AND ENVIRONMENT Heredity and Environment

Chapter 2 HEREDITY AND ENVIRONMENT

Heredity and Environment Chromosomes, Molecular Genetics Gene, and Cell Division Genetic Disorders Behavior Genetics Environmental Influences and Contexts Environment in a Broader Context: Family and Culture

Molecular Genetics 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 genesdelineated pieces of DNA There about 25, 000 genes in human body

Major Features of a Typical Cell

Computer-Generated Stimulation of DNA Molecule 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.

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 What Is 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

Common Proteins and Their Functions in the Human Body

Genes, Chromosomes, and Cell Division 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 23 rd pair determines sex selection and is labeled XX in females and XY in males One’s chromosomal makeup can be visualized in karyotypes

Human Karyotypes

Cell Division and Reproduction Mitosis Cells divide and create two cells with identical sets of chromosomes Meiosis Cell division produces ova and sperm, each of which contain one half of the full set of chromosomes Genotype Genes individual inherits Genes Exist in pairs, each half of which is an allele

Comparison of Mitosis and Meiosis

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

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

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

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

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

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 (4 th ed. ), by R. Lewis, D. Gaffin, M. Hoefnagels, and B. Parker, 2002, New York: Mc. Graw-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 Epigenetic modifications may be transmitted to next generation via genetic inheritance Gene-environment interactions occur at many levels Experience in life can have dramatic effect on later developmental outcomes

Some Sex-Linked Disorders Fragile X syndrome Klinefelter syndrome (XXY, XXXXY) Supermale syndrome (XYY, XYYYY) Chromosomal Color blindness, X-linked Superfemale syndrome (XXX, XXXXX) Some sex -linked disorders Turner Syndrome (OX)

Autosomal Disorders Huntington’ s Disease PKU Cystic Fibrosis Tay-Sachs Chromosoma l (an extra chromosome) Angelman syndrome Genetic (recessive or dominant alleles) Sickle-cell trait Autosomal disorders Down syndrome

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

Video Clip Description of different types of genetic testing: http: //www. youtube. com/watch? v=d. Juo 937 gz 44

Video Clip BBC documentary on Designer Babies with commentary by Princeton professor Lee Silver: http: //www. youtube. com/watch? v=TN 9 ep 4 B 9 Hw 0 &feature=Play. List&p=C 7 E 239 A 945 F 4 C 4 BA&playn ext=1&playnext_from=PL&index=56

Behavior genetics 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 Studies Adoption Studies Twin Studies • Studies how adopted children resemble their adoptive versus their biological parents • Compares identical twins for traits thought to be heritable • Hard to interpret because no twin’s environment is identical, even within same home

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

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

Family and Culture 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

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

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

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

A Lifespan Profile on Influences

Development in a Broad Context Lifespan development is a complex interaction among several important factors Mediating factors—gender, ethnicity, socioeconomic background— determine how broader culturalhistorical forces will be experienced The family will shape one’s experience in important ways Each person’s unique personal characteristics will determine how they act in and adapt to the broader context in which life unfolds