Copyright © 2010 Pearson Education, Inc. All rights reserved. Heredity and Environment Chapter 2 2

Copyright © 2010 Pearson Education, Inc. All rights reserved. Heredity and Environment Molecular Genetics Genes, Chromosomes, and Cell Division Genetic and Chromosomal Disorders Behavior Genetics Environmental Influences and Contexts Environment in a Broader Context: Family and Culture

Copyright © 2010 Pearson Education, Inc. All rights reserved. Molecular Genetics Genetic instructions are found in the DNA molecules found in the nucleus of each cell DNA is a complex molecule made up of nucleotides and four different bases. The bases form base pairs that should not vary The basic units of inheritance are genes, which are delineated pieces of DNA. There are about 25,000 genes in the human body

Copyright © 2010 Pearson Education, Inc. All rights reserved. A Cell of the Human Body SOURCE: Figure “A bodily cell,” In M. R. Cummings (Ed.), Human heredity: Principles and issues (4th ed., p. 16). Pacific Grove, CA: Books/Cole. Copyright ｩ Reprinted with permission of Wadsworth, an imprint of the Wadsworth Group, a division of Thomson Learning. Fax

Copyright © 2010 Pearson Education, Inc. All rights reserved. Computer Simulated DNA Molecule

Copyright © 2010 Pearson Education, Inc. All rights reserved. Segment of DNA Visualized as a Ladder

Copyright © 2010 Pearson Education, Inc. All rights reserved. Protein Synthesis The most significant thing genes do is build proteins Proteins are the molecules that control life Over 200,000 different proteins have been identified in humans

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Genes, Chromosomes, and Cell Division When a cell divides, the 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 The 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

Copyright © 2010 Pearson Education, Inc. All rights reserved. Human Karyotypes

Copyright © 2010 Pearson Education, Inc. All rights reserved. Cell Division and Reproduction Cells divide in a process called mitosis, which creates two cells with identical sets of chromosomes Meiosis is the cell division process that produces ova and sperm, each of which contain one half of the full set of chromosomes The genotype refers to the genes an individual inherits Genes, like chromosomes, exist in pairs, each half of which is an allele

Copyright © 2010 Pearson Education, Inc. All rights reserved. Comparison of Mitosis and Meiosis

Copyright © 2010 Pearson Education, Inc. All rights reserved. From Genotype to Phenotype All of a person’s pairs of alleles form the person’s genotype, or genetic code Some alleles are dominant over others, for instance the allele for brown eyes Others are recessive, such as the allele for blue eyes Two recessive alleles are needed to express a recessive trait But it only takes one dominant allele for a dominant trait to be expressed

Copyright © 2010 Pearson Education, Inc. All rights reserved. Examples of Dominant-Recessive Gene Combinations

Copyright © 2010 Pearson Education, Inc. All rights reserved. Genetic Inheritance Nearly all human characteristics are polygenic: determined by more than one gene pair Some traits are sex-linked, usually passed on by the X chromosome –Since men have only one “X,” they are at risk for traits associated with the X chromosome Genetic mutations may occur during mitosis or meiosis, when the DNA molecule is altered during cell division Mutations may be beneficial or detrimental

Copyright © 2010 Pearson Education, Inc. All rights reserved. Genetic and Chromosomal Disorders About 3% are born with congenital anomalies, or birth defects Genetic anomalies involve problems with the instructional mechanism of the genetic process Sex-linked disorders can occur when the gametes do not replicate correctly or when genetic information, even entire chromosomes, are missing or duplicated

Copyright © 2010 Pearson Education, Inc. All rights reserved. Some Sex-Linked Disorders Color blindness, X-linked Chromosomal Fragile X syndrome Klinefelter syndrome (XXY, XXXY, XXXXY) Superfemale syndrome (XXX, XXXX, XXXXX) Supermale syndrome (XYY, XYYY, XYYYY) Turner Syndrome (OX)

Copyright © 2010 Pearson Education, Inc. All rights reserved. Autosomal Disorders Genetic (recessive or dominant alleles) Angelman syndrome Cystic Fibrosis Huntington’s Disease PKU Sickle-cell trait Tay-Sachs Chromosomal (an extra chromosome) Down syndrome

Copyright © 2010 Pearson Education, Inc. All rights reserved. Genetic Research Uses recombinant DNA technology to reconstruct cells and genes Gene therapies involve reinserting genetically- altered cells into a person –Used to produce a variety of proteins, such as insulin In vivo gene therapy removes some viral genes, inserts cloned normal genes, and retrovirus is reintroduced to patient

Copyright © 2010 Pearson Education, Inc. All rights reserved. Video Clip Description of different types of genetic testing:

Copyright © 2010 Pearson Education, Inc. All rights reserved. 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

Copyright © 2010 Pearson Education, Inc. All rights reserved. Behavior Genetics Behavior genetics tries to understand the genetic origins of behaviors Incorporates the view that complex traits are determined by an interaction of heredity and environment Behavioral genetics looks at the statistical correlation, or concordance, of similar characteristics with genes Concordance rates form the basis of estimates of heritability, the proportion of a trait that is thought to result from genetic factors

Copyright © 2010 Pearson Education, Inc. All rights reserved. Behavior Genetics Studies Adoption Studies –Studies how adopted children resemble their adoptive versus their biological parents Twin Studies –Compares identical twins for traits thought to be heritable –Hard to interpret because no twin’s environment is identical, even within same home

Copyright © 2010 Pearson Education, Inc. All rights reserved. Environmental Influences and Contexts Basic Processes that Affect Behavior –Habituation –Classical Conditioning –Operant Conditioning –Social Learning

Copyright © 2010 Pearson Education, Inc. All rights reserved. A Typical Classical Conditioning Procedure

Copyright © 2010 Pearson Education, Inc. All rights reserved. Operant Conditioning Reinforcers increase the likelihood that a behavior will be repeated –Example: A child is given a delicious cookie after saying “please” and becomes more likely to say “please” in the future. Punishments decrease the probability that a behavior will be repeated –Example: A child who misbehaves is scolded and becomes less likely to misbehave in the future

Copyright © 2010 Pearson Education, Inc. All rights reserved. Family and Culture Family systems are at the heart of human behavior Siblings share many similar experiences, but nonshared experiences and relationships also exist Families pay a critical role in orienting him or her to society and culture It is important to avoid ethnocentrism, the tendency to assume that our own beliefs, customs, and values are normal and others are abnormal

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Sociocultural Influences Cultural factors affect a cohort, a group of individuals born during the same historical era There different 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

Copyright © 2010 Pearson Education, Inc. All rights reserved. A Lifespan Profile on Influences

Copyright © 2010 Pearson Education, Inc. All rights reserved. Development in a Broad Context Lifespan development is a complex interaction among several important factors Mediating factors—gender, ethnicity, socioeconomic background—determine how broader cultural-historical 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

Copyright © 2010 Pearson Education, Inc. All rights reserved. Summary Genetic instructions are contained in the DNA molecules found in the nucleus of each of our cells. The basic unit of inheritance is the gene; genes are units of DNA molecules The cells are arranged in chromosomes, and we have 23 pairs of chromosomes in each cell Genotype refers to what our genes are, but phenotype refers to what we actually express, or look like Most human characteristics are caused by more than one pair of genes Some genes are dominant, some recessive

Copyright © 2010 Pearson Education, Inc. All rights reserved. Summary Genetic and chromosomal disorders may cause birth defects and other problems, such as spontaneous abortions Genetic tests today allow prospective parents to learn if their baby might have genetic defects. Through genetic counseling they can assess the risk of carrying the baby to term Behavior genetics studies how genes impact human behavior But human behavior is never caused by genes alone, rather there are complex interactions between our genes and the environment

Copyright © 2010 Pearson Education, Inc. All rights reserved. Summary Environmental influences on our genes can be very specific events in our individual lives, or they can occur broadly across cultures Learning is one of the primary environmental factors that shape our development. Major forms of learning include: Classical and operant conditioning Social learning All development takes place in the broader context of family and culture Thus, hereditary and environmental forces continually interact as development unfolds