PSYCH 212 Chapter 3
PSYCH 212 Chapter 3 Psych 212
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This 13 page Class Notes was uploaded by Julie Notetaker on Tuesday May 24, 2016. The Class Notes belongs to Psych 212 at Pennsylvania State University taught by Dr. Hunt in Summer 2016. Since its upload, it has received 20 views. For similar materials see Developmental Psychology in Psychlogy at Pennsylvania State University.
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Date Created: 05/24/16
Conception Theories l Hippocrates said that a fetus results from the joining of male and female seeds l Aristotle said that the woman is only a receptacle and that the child is formed entirely by the sperm. Male babies were natural but female babies only came if development was disturbed l Animalculists: said that fully formed little people were contained in the heads of sperm, ready to grow when deposited into the womb l Ovists: inspired by William Harvey, that a female’s ovaries contained tiny humans whose growth was activated by sperm l Kaspar Friedrich Wolff in late 18th century said that there was a gradual building up of structures. Groups of cells that were initially unspecialized differentiated into various tissues, organs, and systems. Later supported by Xavier Bichat Fertilization: union of sperm and ovum to produce a zygote; also called conception l Zygote: one-celled organism resulting from fertilization l Gametes: sex cells (sperm and ovum) l Zygote duplicates itself again and again by cell division to produce all the cells that make up a baby l At birth, a girl is believed to have about 2 million immature ova in her two ovaries, each ovum in its own small sac, or follicle. In a sexually mature woman, ovulation occurs once every 28 days until menopause l Ovulation: rupture of a mature follicle in either ovary or expulsion of its ovum. The ovum is swept along through one of the fallopian tubes by tiny hair cells, called cilia, toward the uterus, or womb l Sperm are produced in the testicles of a mature male at a rate of several hundred million a day and are ejaculated in the semen at climax l Once in the vagina, they try to swim through the cervix into the fallopian tubes, but only a tiny fraction make it that far l Fertilization normally occurs while the ovum is passing through the fallopian tube. If fertilization does not occur, the ovum and any sperm die. The sperm is absorbed by woman’s white blood cells and ovum passes through the uterus and exits through the vagina l Multiple births l Dizygotic twins: fraternal twins resulting from two separate eggs being fertilized by two different sperm to form two unique individuals l Tend to run in families and are the result of multiple eggs being released at one time l Passed from a woman’s mother, when it skips generations, it is normally because a mother has only sons whom she cannot pass the gene to l Black women are more likely to have twins than whites who in turn are more likely than Asian women l Monozygotic twins: identical twins resulting from the cleaving of one eggs and are genetically identical l Twin-to-twin transfusion syndrome: blood vessels of the placenta form abnormally and the placenta is shared unequally among the twins. While mortality is high, if they both survive, they appear different at birth l Rate of 4/1000 births is constant at all times and places l Semi-identical twins: result of two sperm cells fusing with a single ovum which then splits into two separate zygotes l More similar than fraternal twins but less similar than identical twins l Only one case thus far l Incidence of multiple births in US has grown since 1980. But birthrate for triplets and higher multiples has taken a 21% downturn l Trend toward delayed childbearing and increased use of fertility drugs, and IVF l Multiple births associated with increased risks, premature delivery, low birth weight, disability or death of infant l Among 249 mothers who used ART, each additional child increased the risk of maternal depression, more than doubled the chances of a lower quality of life, and sense of stigma, and quadrupled chance of meeting basic material needs l American Society of Reproductive Medicine recommends limitations on artificial procedures involving 3 or more embryos Infertility: inability to conceive after 12 months of trying l Women’s fertility declines in late 20s, and men ‘s declines in late 30s l Ancient doctors advised men to eat fennel and women to drink the saliva of lambs and wear necklaces of earthworms. After sex, women were to lay flat with legs crossed avoid becoming angry l Causes l Men l Most common cause is production of too few or insufficiently motile sperm. A sperm count lower than 60-200 million per ejaculation makes conception unlikely l An ejaculatory duct may be blocked, preventing exit of sperm l Sperm may not be able to swim well enough to reach cervix l Some men appear to have gene mutations or chromosome deletions affecting the quality and quantity of sperm they produce l Women l Failure to produce ova or produce normal ova l Mucus in cervix, preventing sperm from penetrating l Disease of uterine lining, preventing implantation of fertilized ovum l After age 30, deterioration in quality of ova l Most common is blocking of fallopian tubes, preventing ova from reaching the uterus l Treatments l Hormone treatment, drug therapy, or surgery l Fertility drugs increase the likelihood of multiple, high risk birth l Men may take daily supplements of coenzyme Q10 to increase sperm motility. But men increase risk of producing sperm with chromosomal abnormalities l Unless there is a known cause for failure to conceive, the chances of success after 18 motnhs-2 years are high l Assisted reproductive technology ART: methods used to achieve conception through artificial means l Louise Brown was first “test-tube baby” 1978 by Patrick Steptoe and Robert Edwards l In vitro fertilization IVF: a woman receives fertility drugs to stimulate the production of multiple ova. . The ova are surgically removed, fertilized in a laboratory dish, and implanted in the woman’s uterus. These are less likely to become established in the womb and more likely to result in miscarriage l Often multiple ova are implanted to increase odds of pregnancy, but it increases the likelihood of multiple, premature births l Women are cautioned not to engage in sexual activity before removal of eggs because they risk fertilization of multiple eggs l Intracytoplasmic sperm injection ICSI: single sperm injected into the ovum l Used in majority of IVF l Single infants conceived through IVF or ICSI are 2-4x more likely to have certain types of heart defects, cleft lip, and gastrointestinal defects l In vitro maturation IVM: performed earlier in monthly cycle, when egg follicles are developing. Harvesting a large number of follicles before ovulation is complete and then allowing them to mature in the lab can make hormone injections unnecessary and diminish likelihood of multiple births. l Artificial insemination: injection of sperm into a woman’s vagina, cervix, or uterus l Used if man has low sperm count l Artificial insemination by donor AID: if man is infertile l If there is no known cause of infertility, chance of success can be increased by stimulating ovaries to produce excess ova and injecting semen directly into uterus l Only 35% of women who attempted ART in 2005 had live births l Ovum transfer: a donor egg, provided by a fertile younger woman is fertilized in a lab and implanted in the prospective mother’s uterus l Highly successful l Alternatively the ovum can be fertilized in the donor’s body by artificial insemination. The embryo is retrieved from the donor and inserted into the recipient’s uterus l Gamete intrafallopian transfer GIFT or zygote intrafallopian transfer ZIFT: either the egg and sperm or the fertilized egg are inserted in the fallopian tube l Surrogate mother: fertile woman who is impregnated by the prospective father, usually by artificial insemination. She agrees to carry the baby to term and give it to the father and his partner l Courts in most states view surrogacy contracts as unenforceable and some states have either banned the practice or place strict conditions on it l American Academy of Pediatrics AAP Committee on Bioethics recommended that surrogacy be considered a tentative, preconception adoption agreement and recommends a pre-birth agreement on the period of time in which a surrogate may assert parental rights Heredity: the genetic transmission of heritable characteristics from parents to offspring l Deoxyribonucleic acid DNA: chemical that carries inherited instructions for the development of all cellular forms of life l Double-helix structure composed of base pairs of Thymine and Adenine and Guanine and Cytosine l Genetic code: sequence of bases within the DNA molecule; a set of rules that govern the formation of proteins that determine the structure and functions of living cells l Chromosomes: coils of DNA that consist of genes l Genes: small segments of DNA located in definite positions on particular chromosomes; functional units of heredity l The sequence of bases in a gene tells the cell how to make the proteins that enable it to carry out its specific functions l Human genome: complete sequence of genes in the human body l Reference point that shows the location of all human genes l Every cell in the human body except sex cells has 23 pairs of chromosomes, 46 in all l Through meiosis, type of cell division, each sex cell ends up with only 23 chromosomes, one of each pair. Thus a zygote ends up with 46, 23 from each parent l Mitosis: process by which nonsex cells divide in half over and over again, and DNA replicates itself. As cells divide, they differentiate, specializing in a variety of bodily functions l Genetic action that triggers the growth of body and brain is often regulated by hormonal levels, both in mother and developing baby l Human genome has changed in response to environmental conditions l One team estimated that at least 7% of genome has been evolving during past 40,000 years at a faster rate than ever before due to changes in diet and new diseases such as AIDS, malaria, and yellow fever l After agricultural revolution, when farmers switched from hunting animals to milking them, a new gene that enabled digestion of lactose spread to 80% of European population. But lactose intolerance is still common in Asia and Africa where dairy is less widespread l Gender l Autosomes: 22 chromosomes not related to sexual expression l Sex chromosomes: 23rd chromosome which governs the baby’s sex l Every ovum gives an X chromosome, but sperm contains X or Y l Y chromosome contains SRY gene l When zygote is XX it is female, when XY it is male l Initially, the embryo’s reproductive system is almost identical. 6-8 weeks after conception, male embryos start producing testosterone l Exposure of a genetically male embryo to steady high levels of testosterone ordinarily results in development of a male body with male sexual organs l Research with mice has found that hormones must first signal the SRY gene, which then triggers cell differentiation and formation of the testes. Without this signaling, a male mouse will develop female genitals instead of male ones l Development of female reproductive system depends on signaling of molecule called Wnt-4, a variant form of which can masculinize a genetically female fetus l Researchers discovered that only 75% of genes on the extra X chromosome for women are inactive. About 15% are active and 10% are active in some women but not others l May explain why women are healthier and live longer, harmful changes in a gene on one X chromosome may be offset by a backup copy l 1860s Gregor Mendel crossbred pea plants that produced only yellow seeds with pea plants that produced only green seeds. The resulting hybrids produced only yellow seeds, which meant they were dominant over green. When he bred yellow hybrids with each other, only 75% had yellow seeds, which meant that a trait can be recessive l Recessive: carried by an organism that does not express or show it l He tried breeding two traits at once, round yellow seeds with green wrinkled seeds and found that color and shape were independent of each other l Particulate inheritance: hereditary traits are transmitted separately l Alleles: two or more alternative forms of a gene that can occupy the same position on paired chromosomes and affect the same trait l People receive one maternal and one paternal allele for each trait l Homozygous: possessing two identical alleles for a trait l Heterozygous: possessing differing alleles for a trait l Dominant inheritance: pattern of inheritance in which, when a child receives different alleles, only the dominant one is expressed l Recessive inheritance: pattern of inheritance in which a child receives identical recessive alleles, resulting in the expression of a nondominant trait l Polygenic inheritance: pattern of inheritance in which multiple genes at different sites on chromosomes affect a complex trait l While single genes often determine abnormal traits, there is no single gene by itself that can account for individual differences in any complex normal behavior l Mutations: permanent alterations in genes or chromosomes that usually produce harmful characteristics but provide the raw materials of evolution l Multifactorial transmission: combination of genetic and environmental factors to produce certain complex traits l Phenotype: observable characteristics of a person l Product of genotype and any relevant environmental influences l Genotype: genetic makeup of a person, containing both expressed and unexpressed characteristics l Epigenesis/ epigenetics: mechanism that turns genes on or off and determines functions of body cells l Affected by a continual bidirectional interplay with nongenetic influences l Chemical molecules attached to a gene that alter the way a cell reads the gene’s DNA. Because every cell inherits the same DNA sequence, the function of the chemical tags is to differentiate various types of body cells l Epigenetic changes can occur throughout the lifespan in response to environmental factors such as nutrition, sleep habits, stress, and physical affection l Errors can lead to disease l One twin study showed epigenetic differences in 35% of the sample associated with age and lifestyle factors l Explains why one twin could be susceptible to disease such as schizophrenia and one is not l Cells are particularly susceptible to epigenetic modification during critical periods such as puberty and pregnancy. And modifications, especially early in life, can be heritable l Genome/genetic imprinting: differential expression of certain genetic traits, depending on whether the trait has been inherited from mother or father. In imprinted gene pairs, genetic information inherited from the parent of one sex is activated while the information from the other parent is suppressed l When normal imprinting patterns are disrupted, abnormal fetal growth or congenital growth disorders may result l Evolutionary theory says that father benefits from having large offspring with minimal cost, while women incur the cost of bearing a large infant. Thus fathers imprint growth enhancing genes such as IGF2, whereas mothers silence those genes, keeping a fetus’s growth balanced in order to preserve bodily resources l If both parents’ copies of a growth-enhancing gene are expressed, a fetus will be overgrown. If both copies are silenced, the growth will be restricted l Helps explain why children who receive a certain allele from their mothers are more likely to have autism than those who receive that allele from their fathers Genetic abnormalities l Birth disorders affect only abut 3% of live births but are leading cause of infant death in US, accounting for 19.5% of all deaths in first year l Although they can be quite serious, defects transmitted by dominant inheritance are less likely to be lethal at an early age than those transmitted by recessive inheritance l If a dominant gene is lethal at an early age, then affected children would be likely to die before reproducing, therefore that gene would not be passed on l Because recessive genes are not expressed if the parent is heterozygous for that trait, it may not always be apparent that a child is at risk for receiving two alleles of a recessive gene n Certain ethnic groups are more likely to carry particular recessive genes, so this can be used to gauge likelihood of child being affected l Incomplete dominance: pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait n People with only one sickle-cell allele and one normal allele do not have sickle-cell anemia with abnormally shaped blood cells, nor are they normal round, they are an intermediate shape l Sex-linked inheritance: pattern of inheritance in which certain characteristics carried on the X chromosome inherited from the mother and transmitted differently to her male and female offspring n In humans, the Y chromosome is smaller and carries far fewer genes than the X chromosome. Males receive only one copy of any gene carried on the sex chromosome and females receive two copies n If a woman has a bad copy of a particular gene, she has a backup copy. If a male has a bad copy of a particular gene, that gene will be expressed n Heterozygote females who carry one bad copy of a recessive gene and one good copy are called carriers u If she has children with an unaffected male, she has a 50% chance of passing the disorder to any sons they may have because the father must have contributed the Y, so the X has a 50% chance of being the good or bad gene from mother l Daughters may be protected because father will pass good copy of gene from father. Thus they have 50% chance of being unaffected, or carrying a hidden recessive copy of the gene u If the mother was a carrier and the father had a bad gene, it is possible for a female to inherit a sex-linked condition u Sex-linked recessive disorders are more common in men l Red-green color blindness, hemophilia, Duchene muscular dystrophy Chromosomal abnormalities l Typically occur due to errors in cell division, which result in an extra or missing chromosome. Some of these errors happen in the sex cells during meiosis o Likelihood of errors in meiosis may increase in offspring of women age 35 or older l Sex chromosome abnormalities o XYY 1 in 1000 male births Tale stature Tendency to low IQ, especially verbal No special treatment o XXX (triple X) 1 in 1000 female births Normal appearance Menstrual irregularities Learning disorders, mental retardation Special education o XXY (Kleinfelter syndrome) 1 in 1000 male births Sterility, small testes Underdeveloped secondary sex characteristics Learning disorders Hormone therapy and special education o XO (Turner syndrome) 1 in 1500-2500 female births Results from missing X chromosome Short stature, webbed neck Impaired spatial abilities No menstruation, infertility, underdeveloped sex organs Incomplete development of secondary sex characteristics Hormone therapy and special education o Fragile X 1 in 1200 male births; 1 in 2000 female births Minor to severe mental retardation Symptoms more severe in males Delayed speech and motor development Hyperactivity Most common form of mental retardation l Down syndrome: chromosomal disorder characterized by moderate to severe mental retardation and by such physical signs as a downward sloping skin fold at the inner corners of the eyes o Most common genetic disorder in children, 1 in 700 babies born alive o Known as trisomy-21 because it is characterized by an extra 21 chromosome in 90% st of cases, or in 3-4% of cases, by the translocation of part of the 21 chromosome onto another chromosome before or at conception o Translocation: rearrangement of genetic material within the same chromosome or the transfer of a segment of one chromosome to another nonhomologous one o Slowed growth, poor muscle tone, congenital heart defects, thick hands o Ear infections, and early hearing loss, gastrointestinal defects or issues o Impaired communication, language, memory, and motor skills o Although risk of having down syndrome child rises with age, because of the higher birthrates of younger women, there are more young mothers with children with Down syndrome 95% of cases the extra chromosome comes from the mother, 5% the father o Brains appear normal at birth but shrink in volume by young adulthood, particularly in the hippocampal area and prefrontal cortex, resulting in cognitive dysfunction, and in the cerebellum, causing problems with motor coordination and balance o Children benefit cognitively, socially, and emotionally when placed in regular classrooms than in special schools and when provided with regular intensive therapies designed to help them achieve important skills o As adults many live in small group homes and support themselves; and do well in structured job situations o More than 70% live into 60s but they are at elevated risk of early death from various causes such as leukemia, cancer, Alzheimer’s, cardiovascular disease th l Edwards syndrome: a condition in which a child is born with an extra 18 chromosome and suffers from a variety of birth defects, including abnormalities of the heart, kidneys, gastrointestinal system, and brain l Genetic counseling: clinical service that advises prospective parents of their probable risk of having children with hereditary defects o Since so many Jewish couples have been tested for Tay-Sachs, far fewer Jewish babies have been born with the disease o Genetic counselor takes a family history and gives prospective parents and any biological children physical examinations. Blood, skin, urine, or fingerprints tested o Karyotype: chart showing chromosomes from body tissues that are arranged and photographed, and photographs are enlarged and arranged according to size and structure. Can show chromosomal abnormalities and can indicate whether a person who appears normal might carry a genetic defect that could be transmitted to a child l Genetic testing o Genomics: scientific study of the functions and interactions of the various genes o Medical genetics: the application of genetic information to therapeutic purposes o Scientists are able to identify genes that cause, trigger, or increase susceptibility to particular disorders and tailor drug treatments to specific individuals o Some courts have ruled that blood relatives have a legitimate claim to information about a patient’s genetic health risks that may affect them, even though such disclosures violate confidentiality o Genetic determinism: misconception that a person with a gene for a disease is bound to get the disease o Genetic Information Nondiscrimination Act 2008 prohibits discrimination based on genetic testing o Experts recommend against testing for diseases where there is no cure o Could be used to justify the sterilization of people with wrong genes or abortions o Gene therapy: experimental technique for repairing or replacing defective genes or regulating the extent to which a gene is turned on or off Has successfully treated congenital blindness, advanced melanoma, and myeloid blood disorders Nature and Nurture l Behavioral genetics: quantitative study of relative heredity and environmental influences on behavior o Heritability: statistical estimate of contribution of heredity to individual differences in a specific trait within a given population at a particular time If the environment exerts a large influence on a trait, people who live together should be more similar on traits than people who do not live together, and this variable can be used to determine heritability Heritability is expressed as a percentage ranging from 0.0-1.0. The higher the number, the greater the heritability. An estimate of 1.0 would meant hat genes are 100% responsible, 0% would mean that environment shaped the trait Does not refer to influences that shaped any one person because those influence are impossible to separate. And does not tell us how traits develop Family studies: measure the degree to which biological relatives share certain traits and whether the closeness of the familial relationship is associated with the degree of similarity Cannot rule out environmental influences Adoption studies: look at similarities between adopted children and their adoptive families and also between adopted children and their biological families Twin studies: compare pairs of monozygotic twins with same-sex dizygotic twins Same sex twins used to avoid confounding effects of gender Concordant: term describing the tendency of twins to share the same trait or disorder When monozygotic twins are more concordant on a trait than dizygotic twins, the likelihood of a genetic factor can be studied further through adoption studies Studies of monozygotic twins separated in infancy and reared apart have found strong resemblances between the twins o Critics of behavioral genetics claim that its methods tend to maximize importance of hereditary effects and minimize environmental ones. They say that a high heritability estimate, does not imply that the environment should not be able to make a difference in the expression of that trait Great variations depending on source of data. Twin studies suggest more heritability than adoption studies do o Even if a trait is strongly influence by heredity, environmental interventions can overcome genetically determined conditions l Developmental system: from conception on, a combination of constitutional (biological and psychological), social, economic, and cultural factors help shape development o Reaction range: potential variability, depending on environmental conditions, in the expression of a hereditary trait Body size depends largely on biological processes, but a range of sizes is possible depending on environmental opportunities and constraints and a person’s own behavior Heredity can influence whether a reaction range is wide or narrow. The genotype places limits on the range of possible phenotypes o Canalization: limitation on variance of expression of certain inherited characteristics After a storm, the rainwater needs to go somewhere. If a street has deep canals, the rain will go down there. It would take an extreme change in environment to alter the water’s course. Highly canalized traits are strongly programmed by genes and there is little opportunity for variance in their expression Normal babies follow predictable sequence of motor development: crawling, walking, running. The sequence is canalized because children will follow this blueprint irrespective of the environment Many highly canalized traits tend to be necessary for survival. Natural selection has designed them in a predictable and reliable way within a variety of environments Cognition and personality are not highly canalized, they are more subject to experience l Genotype-environment interaction: effect of the interaction between genes and the environment on phenotypic variation o Genotype-environment correlation: tendency of certain genetic and environmental influences to reinforce each other, also called geneotype-enviroment covariance Passive correlations: parents, who provide the genes that predispose a child toward a trait, also tend to provide an environment that encourages the development of that trait. The child does not control it; they have inherited the genes and environment. Typically relates to young children Only function when a child is living with a biologically related parent Reactive, or evocative correlations: children with differing genetic makeup evoke different responses from adults Active correlations: as children get older and have more freedom to choose their own activities, they actively select experiences consistent with their genetic tendencies Niche-picking: tendency to seek out environments compatible with one’s genotype l Nonshared environmental effects: the unique environment in which each child grows up, consisting of distinctive influences or influences that affect one child differently from another o Parents could treat siblings differently, illnesses or accidents, experiences outside the home Some characteristics influenced by heredity and environment Obesity o 40-70% of risk is genetic, but environmental influences contribute o A key gene on chromosome 10 normally controls appetite, but an abnormal version stimulates hunger and overeating. Another allele restricts the activity of dopamine, which normally signals when a person is full o The kind of food eaten, how much exercise is encouraged in a particular home can increase or decrease the likelihood Intelligence o Polygenic trait, it is influenced by the additive effects of a large number of genes working together o Depends of brain size and structure o Adopted children’s IQs are closer to biological parents than adopted parents o Genetic influence increases with age as a result of niche-picking o Nonshared environment is influential throughout the life-span and is primarily responsible for changes in cognitive performance Personality o 40-50% heritability of personality traits and little evidence of shared environmental influence o Genes directly linked to neuroticism may contribute to depression and anxiety o Temperament: characteristic disposition or style of approaching and reacting to situations Largely inborn and consistent over the years but responds to special experiences and parental handling Twins and siblings tend to be similar in temperament Psychopathology o Mental disorders such as schizophrenia, autism, alcoholism, and depression tend to run in families but an inherited tendency can be triggered by environmental factors o Schizophrenia: neurological disorder marked by loss of contact with reality; hallucinations and delusions; loss of coherent, logical thought, and inappropriate emotionality Heritability 80-85% A wide array of gene mutations may increase susceptibility Exposure to influenza or mother’s loss of close relative during first trimester of nd rd pregnancy, maternal rubella or respiratory infections in the 2 and 3 trimesters Infants in urban areas or late winter or early spring are at increased risk Fetal malnutrition, mothers with obstetric complications or were poor or severely deprived Advanced paternal age, over 30 years
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