Chapter 3 Notes
Chapter 3 Notes PSYC 225
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This 11 page Class Notes was uploaded by Ashley Notetaker on Friday September 11, 2015. The Class Notes belongs to PSYC 225 at Northern Illinois University taught by Elizabeth Rusnak in Summer 2015. Since its upload, it has received 136 views. For similar materials see Lifespan Development: Child-Adult in Psychlogy at Northern Illinois University.
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Date Created: 09/11/15
Forming a New Life Ch 3 How Fertilization Takes Place Fertiization Union of sperm and ovum to produce a zygote Point of conception Zygote Onecelled organism resulting from fertilization Contains 23 chromosomes from each parent Women are born with roughly 2 million ova each in its own follicle small sac Sexually mature women ovulate once every 28 days Egg travels through the fallopian tubes to the uterus A mature male produces sperm at a rate of several hundred million a day Sperm try to swim through the cervix to the fallopian tubes Released at sexual climax lf released during sex sperm try to swim through the cervix to the fallopian tubes many don t make it What Causes Multiple Births Dizygotic Twins Twins conceived by the union of two different ova or an ovum that has split with two different sperm cells Fraterna twins no more alike genetically than regular siblings May run in families Monozygotic Twins Twins resulting from the division of a single zygote after fertilization ldentica twins genetically similar Occur by chance Semildentical Twins The result of two sperm cells fusing with a single ovum More genetically similar than dizygotic twins but less similar than monozygotic twins Rare Rate of monozygotic twins is 4 per 1000 live births Rate of dizygotic twins varies More likely in West African and African American women than Caucasian women More likely in Caucasian than Chinese orJapanese women Incidence of multiple births has increased recently What Determines Sex A child s sex is genetically determined by the father s sperm Sex Chromosomes Pair of chromosomes that determines sex XX in the normal human female XY in the normal human male Every ovum is an X chromosome Sperm can be either an X or Y chromosome Y chromosome contains the gene for maleness SRY gene Patterns of Genetic Transmission Dominant and Recessive Inheritance Alleles Two or more alternative forms of a gene that occupy the same position on paired chromosomes and affect the same trait Homozygous Possessing two identical alleles for a trait Heterozygous Possessing differing alleles for a trait Dominant Inheritance Pattern of inheritance in which when a child receives different alleles heterozygous only the dominant one is expressed Recessive Inheritance Pattern of inheritance in which a child receives identical homozygous recessive alleles resulting in expression of a nondominant trait Freckles are a dominant trait controlled by a single gene Poygenic Inheritance Pattern of inheritance in which multiple genes at different sites on chromosomes affect a complex trait Mutations Permanent alterations in genes or chromosomes that may produce harmful characteristics EpigeneticsEpigenesis Mechanism that turns genes on or off and determines functions of body cells Genotypes and Phenotypes Multifactorial Transmission Phenotype Observable characteristics of a person ysical appearance Genotype Genetic makeup of a person Contains both expressed and unexpressed characteristics Genetic and Chromosomal Abnormalities Babies with serious birth defects are at a high risk of dying shortly after birth or during infancy and childhood Most birth disorders are rare Affect about 3 of live births Leading cause of infant death in the United States In 2007 they accounted for 195 of all deaths in the rst year Dominant or Recessive Inheritance of Defects Norma genes are usually dominant When an abnormal gene is dominant and a parent is heterozygous for the gene the children have a 5050 chance of inheritance 1800 disorders are transmitted by dominant inheritance including achondroplasia and Huntington s disease These defects are less likely to be lethal at an early age Recessive defects are only expressed if the child is homozygous for the gene If the parents are heterozygous they may not know their child is at risk lncudes disorders like TaySachs and cystic brosis Defects passed on through recessive inheritance tend to be lethal at an earlier age SexLinked Inheritance of Defects SexLinked Inheritance Pattern of inheritance in which certain characteristics carried on the X chromosome inherited from the mother are transmitted differently to her male and female offspring lncudes hemophilia and color blindness Males are more likely to be affected by traits carried on the X chromosome because they only have one whereas females have two Femaes may be affected if their father has the condition and their mother is a carrier Chromosomal Abnormalities Typicaly occur because of errors in cell division Results in an extra or a missing chromosome Some errors happen during meiosis like Klinefelter XXY and Turner XO syndromes These errors may be increased in the offspring of women age 35 and older Other abnormalities occur in the autosomes Down syndrome Chromosomal disorder characterized by moderatetosevere mental retardation and by such physical signs as a downwardsloping skin fold at the inner corners of the eyes Trisomy 21 Accounts for 40 of all cases of moderateto severe mental retardation Affects roughly 1 in 700 live births Risk increases with mothers age though a higher number of young mothers have children with Down syndrome Prenatal Development First clear sign of pregnancy is usually a missed period Gestation Period of development between conception and birth Usualy 3741 weeks Gestational Age Age of an unborn baby usually dated from the rst day of an expectant mother s last menstrual cycle Stages of Prenatal Development Three stages Germinal Embryonic Feta Developmental process occurs from the top down and from the center of the body outward Germinal Stage Fertilization to 2 weeks First 2 weeks of prenatal development characterized by Rapid cell division Blastocyte uid lled sphere formation lmpantation in the wall of the uterus About 6 days after fertilization In the rst 36 hours the zygote rapidly divides and duplicates As it is dividing the ovum is making its way to the uterus Form changes to a blastocyte udi lled sphere which eventually implants itself in the uterine walla bout 6 days after fertilization Only 1020 of zygotes complete implantation and continue to develop Embryonic Stage 2to 8 weeks Second stage of gestation characterized by Rapid growth Development of major body systems and organs Critica period during which the embryo is most vulnerable to destructive in uences Most severely defective embryos usually do not survive beyond the rst trimester 3 month period Spontaneous Abortion Natura expulsion from the uterus of an embryo that cannot survive outside the womb After 20 weeks it is generally characterized as a stillbirth Occurs in about 1 in 4 recognized pregnancies but could be as high as 1 in 2 pregnancies 5070 involve chromosomal abnormalities Smoking drinking alcohol and drug use increase the risk More common among African American Native American and Alaskan native women Both younger and older mothers ln pregnancies with twins or higher order multiples Males are more likely to be spontaneously aborted or to be stillborn More likely to die early in life and at every age they are more susceptible to many disorders Feta Stage 8 weeks to Birth Fina stage of gestation characterized by lncreased differentiation in body parts Greatly enlarged body size A fetus breathes kicks turns exes their body does somersaults squints swallows makes sts hiccups and can suck its thumb A fetus can also feel pain presumably around the third trimester Male fetuses are more active and tend to move more vigorously Mature taste cells appear around 14 weeks of gestation The sense of smell is also well developed before birth Responses to sound and vibration begin at 26 weeks of gestation increase and then plateau around 32 weeks Environmental In uences Maternal Factors The mother s body is the prenatal environment Everything that in uences her wellbeing may alter the embryofetus environment Teratogen Environmenta agent such as a virus a drug or radiation that can interfere with normal prenatal development and cause developmental abnormalities Environmental In uences Maternal Factors Drug lntake Medical Drugs Originally thought to be stopped by the placenta In the 19605 thalidomide was found to have caused stunted and missing limbs severe facial deformities and defective organs in roughly 12000 babies Other harmful drugs include Tetracycine Certain barbiturates opiates and other CNS depressants Hormones including diethylstilbestrol DES and androgens Anticancer drugs like methotrexate Accutane ACE inhibitors and NSAle such as naproxen and ibuprofen Certain antipsychotics Alcohol Most common cause of mental retardation and the leading preventable cause of birth defects in the United States Fetal Alcohol Syndrome FAS Combination of mental motor and developmental abnormalities affecting the offspring of some women who drink heavily during pregnancy FAS and other less severe alcoholrelated conditions occur in nearly 1 in every 100 births Nicotine Single most important factor in low birth weight in developed countries lncreased risk of Miscarriage Growth retardation Stillbirth Small head circumference Sudden infant death Coic uncontrollable extended crying for no apparent reason Longterm respiratory neurological cognitive attentional and behavior problems Caffeine Mixed results Does not appear to be a teratogen for human babies Mothers are at an increased risk for miscarriage though Also increases risk of sudden death in infancy Marijuana Cocaine and Methamphetamine Heavy marijuana use can lead to Birth defects Low birth weight Withdrawallike symptoms at birth lncreased risk of attention disorders and learning problems later in life Prenata use of marijuana has also been linked to lmpaired attention impusivity Dif culty in using visual and perceptual skills after age 3 Cocaine use during pregnancy has been associated with Spontaneous abortion Deayed growth Premature labor Low birth weight Small head size Birth defects lmpaired neurological development Acute withdrawal symptoms and sleep disturbances after birth Some studies have reported no link between prenatal cocaine exposure and physical motor cognitive emotional or behavioral de cits that could not E be attributed to other risk factors Methamphetamineexposed infants are more likely to have low birth weight and to be small for their gestational age Prenatal exposure to methamphetamines has been implicated in fetal brain damage to areas of the brain involved in learning memory and control Fetal Alcohol Syndrome Probems in infancy Reduced responsiveness to stimuli Slow reaction time Reduced visual acuity Probems throughout childhood Short attention span Distractibility ResUessness Hyperactivity Learning disabilities Memory de cits Mood disorders Aggressiveness and problem behavior Environmental In uences Maternal Factors Maternal IHnesses Acquired Immune De ciency Syndrome AIDS Viral disease caused by the human immunode ciency virus HIV that undermines effective functioning of the immune system Perinatal transmission may occur The virus may cross over to the fetus s bloodstream through the placenta during pregnancy labor or delivery or after birth through breast milk Biggest risk is when the mother is unaware she has HIV Rate of perinatal HIV infection is now less than 2 RubeHa German measles If contracted before the 11th week of pregnancy will almost certainly cause deafness and heart defects Chances of infection are greatly reduced in Europe and the United States Toxoplasmosis Can cause Feta brain damage Severely impaired eyesight Seizures Miscarriage Stillbirth Avoid raw or rare meat peel and thoroughly wash raw fruit and vegetables do not dig where cat feces may be buried Diabetes Offspring of mothers with diabetes are 3 to 4 times more likely to develop a wide range of birth defects Blood glucose levels need to be under control BEFORE becoming pregnant Risks can be reduced by using multivitamin supplements for the 3 months prior to conception and the rst 3 months of pregnancy Environmental In uences Paternal Factors Abnormal or poorquality sperm may result from exposure to Lead Marijuana or tobacco smoke Large amounts of alcohol or radiation DES Pesticides High ozone levels Offspring of male workers at a British nuclear processing plant were at elevated risk of being stillborn Fathers who had diagnostic X rays within the year prior to conception or who had high lead exposure tended to have babies with low birth weights and slowed fetal growth Men who smoke are more likely to transmit genetic abnormalities Older fathers may be a signi cant source of birth defects due to damaged or deteriorated sperm Associated with increased risk for rare conditions including dwar sm May be a factor in the higher number of cases of schizophrenia bipolar disorder and autism related disorders
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