Jaymie Ticknor Developmental Psychology 3620 Sect 853 10 September 2013 Chapter 4 How Children Develop Nature Through Nurture Genes nature the basic unit of inheritance genes are made of DNA and they give messages to the body to create proteins that are the basis for the body s development and functioning Genes and environment interact in complex ways to shape development Nature and nurture are inextricably intertwined The History of Research on Genetics Eugenics the historical concept not accepted today that desirable traits can be bred into human beings while undesirable ones can be bred out The Study of Genetics and Behavior How We Study Genes and Behavior Three ways in which genetic effects on behavior have been investigated Molecular genetics is focused at the level of the cell Behavioral genetics is focused at the level of behavior Behavioral genomics connects the behavioral and the cellular levels Molecular Genetics Molecular Genetics research focused on the identification of particular genes to identify how these genes work within the cell Behavioral Genetics Behavioral Genetics research to determine the degree of genetic basis for a behavior trait or ability Studies are based on natural situations such as adoption and twins Behavioral Genomics research that links behaviors with specific genes Behavioral Genomics How Do Genes Work Only 20 000 25 000 genes in humans 99 of the human genome is identical for all human beings Differences account for only one tenth of one percent of our genetic inheritance Our Genetic Beginnings Zygote the fertilized egg that begins to divide into cells that will develop into the embryo Chromosomes the strands of genes that constitute the human genetic endowment 23 matched pairs 22 pairs of chromosomes called autosomes look very similar to each other 23rd pair of chromosomes determine the sex of the child Dizygotic DZ Twins formed when a woman produces two ova or eggs which are fertilized by two sperm genetically DZ twins are as similar as any siblings fraternal twins Women over the age of 35 are more likely to have DZ twins the older she is the greater chance of having a multiple pregnancy After the age of 45 chance of having a multiple birth Monozygotic MZ Twins formed when a woman produces one egg that is fertilized by one sperm and the resulting ball of cells splits to form two individuals with the same genes identical twins Have small differences in the arrangement of their genes may result in observable and sometimes significant differences Chromosomes Genes DNA and Bases GATC Genes are made up of DNA deoxyribonucleic acid DNA consists of two chains of nucleotides the basic unit of DNA that consists of a chemical base a phosphate group and a sugar molecule that twirl around each other in a double helix Four nitrogen containing bases Guanine Cytosine go together Adenine and Thymine go together Gattaca resembles GATC Mendelian Inheritance Dominant and Recessive Genes Genotype or Genome all of a person s genes including those that are active and those that are silent Includes both dominant and recessive genes Phenotype the genetically based characteristics that are actually shown in one s body Sickle Cell Anemia two recessive genes pairing up with each other to create a genetic disorder and disease shape of red blood cells is distorted and can cause a lot of pain can be found in 1 of 500 African Americans However 1 in 10 African Americans with one of these recessive genes appears to protect people from malaria Polygenic Inheritance numerous tens or even hundreds genes may interact together to One Behavior Many Genes One Gene Many Effects promote any particular trait or behavior Pleiotropic Effects any single gene may have many different influences Generalist Genes genes that affect many apparently distinct cognitive abilities Genetic Disorders Single Gene Disorders genetic disorders caused by recessive genes or mutations Chromosome Disorders disorders that result when too many or too few chromosomes are formed or when there is a change in the structure of the chromosome caused by breakage Multifactorial Inheritance Disorders disorders that result from the interaction of many genes in interaction with environmental influences Single Gene Disorders Genetically based disorders can occur in two ways An individual inherits a pair of recessive genes that code for that disorder Mutations changes or mistakes in the formation of genes that occur as cells divide some of the bases that give the instructions to create proteins are out of order or missing Mutations are very common and most do not cause problems for individuals Tay Sachs is an example results in progressive neurological deterioration and death of an infant usually by age 5 Phenylketonuria PKU condition in which the child cannot digest a common protein in the human diet can result in mental retardation Cystic Fibrosis condition in which the child s body produces a thick sticky mucus that clogs the lungs making the child vulnerable to pulmonary infections also associated with nutritional deficiencies cause of this is a missing sequence in a specific gene called the CFTR gene CTT is missing Problems Associated With the Y Chromosome Y chromosome contains the lowest number of genes 70 200 X chromosome contains 900 to 1 400 genes Any genes on the X chromosome that do not have a partner will be expressed whether they are normally recessive or dominant Can result in red green color blindness hemophilia or Duchenne muscular dystrophy Chromosome Disorders Chromosomal disorders occur when one of the 23 pairs of chromosomes contains either one or three chromosomes rather than two or when there is a change in the structure of the chromosome caused by breakage Multifactorial Inheritance Disorders Disorders depression alcoholism schizophrenia autism etc appear to have some genetic input but also can result from the interaction of many genes that also interact with environmental influences Genetic Counseling and Testing Any couple statistically has a 3 chance of having a child with a genetically based disorder Thalassemia a blood disorder associated with reduced production of hemoglobin Alpha fetoprotein test tests of the mother s blood may uncover abnormalities in hormone levels that signal the possibility of neural tube defects such as spina bifida or Down syndrome Amniocentesis a test to look for genetic abnormalities prenatally in which a physician uses a long thin needle to extract amniotic fluid