Presentation on theme: "Invitation to the Life Span by Kathleen Stassen Berger"— Presentation transcript:
1Invitation to the Life Span by Kathleen Stassen Berger Chapter 2 – Genes and Prenatal DevelopmentThese colors actually are a template design in PPT, but match the scheme of the book…do you agree? If so, this will be an easy formatting task. The cover has been revised to reflect the new title “Invitation to the Life Span”. I’ve been waiting to get it, that’s why this slide has been delayed getting to you…but I didn’t want to wait any longer. So the cover needs to be swapped in/out when it arrives. Lastly, I got rid of the chapter outline…as it’s repetitive. Do you agree?PowerPoint Slides developed byMartin Wolfger and Michael JamesIvy Tech Community College-Bloomington
2The Beginning of Life DNA (deoxyribonucleic acid): Chromosomes: Molecule that contains the chemical instructions for cells to manufacture various proteinsPromotes growth and sustains lifeChromosomes:Molecules of DNADNA consists of 46 chromosomes arranged in 23 pairs
3The Beginning of Life Gametes: Zygote: Genes: Reproductive cells (sperm and ova)Each gamete consists of 23 chromosomes.Zygote:Two gametes (sperm and ovum) combine and produce a new individual with 23 chromosomes from each parent.Genes:Specific sections of a chromosome that carry instructions via four chemicals.Chemicals are organized in four pairs (AT, TA, CG, GC).Each person has about 3 billion pairs.
5Genetic Variations and Similarities Genes are passed down from generation to generationGenotype:An organism’s genetic inheritance, or genetic potentialUnique for each organismPhenotype:The observable characteristics of an organism, including appearance, personality, intelligence, and all other traits.
6Genetic Variations and Similarities Many genes are identical for every human being.Some genes vary slightly in their codes from one person to another.Allele:Variation of a gene or any of the possible forms in which a gene for a particular trait can occur.Effects of variations vary greatly from causing life-threatening conditions to having no detectable effect at all.
7The Human Genome Genetic Diversity Genome: Distinguishes each person Allows the human species to adapt to pressures of the environment (e.g. climate changes, illnesses).Genome:The full set of genes that are the instructions to make an individual member of a certain speciesSimilarity between two people: 99.5%Similarity between humans and chimpanzees: 98%Similarity between humans and every other mammal: 90+%
8Human Genome Project and HapMap Found “only” about 20,000 genes in humansExact number is unknownHapMap:International project trying to spot all variations in the human genomeFound 11 million variations among the billion chemical pairs
9Siblings and Twins Sibling Similarities Monozygotic (identical) twins: Each sibling gets abut 10,000 genes from each parent.Millions of variations and billions of combinations are possible.Full siblings are not necessarily alike.Monozygotic (identical) twins:Originate from one zygote that splits apart very early in development.Incomplete split results in conjoined twins.Same genotype but slight variations in phenotype are possible due to environmental influences.
10Siblings and Twins Dizygotic (fraternal) twins Result from fertilization of two separate ova by two separate sperm.Dizygotic twins have half their genes in common and occur twice as often as monozygotic twins.Incidence is genetic and varies by ethnicity and age.
11Male and Female Humans usually possess 46 chromosomes. 44 autosomes and 2 sex chromosomesFemales: XXMales: XYSex of offspring depends on whether the father’s Y sperm or X sperm fertilizes the ovum.
13Genetic Interactions Almost every trait is: Regulator genes polygenic (affected by many genes)multifactorial (influenced by many factors)Regulator genesDirect the interactions of other genes, controlling their genetic expression, duplication, and transcriptionResponsible for differences between species
14Additive Heredity Additive genes Genes that add something to some aspect of the phenotypeEffects of additive genes add up to make the phenotypeExample: Height is affected by the contributions of about 100 genes
15Dominant-Recessive Heredity Dominant gene is far more influential than the recessive gene (non-additive).Dominant gene can completely control the phenotype with no noticeable effect of recessive gene.Genes for blood type B and Rh-positive blood are dominant.Effect of recessive genes can sometimes be noticed.Dominant brown eye gene and recessive blue eye gene can result in hazel eyes.
16CarrierA person whose genotype includes a gene that is not expressed in the phenotypeUnexpressed gene occurs in half of the carrier’s gametes and is passed on to half of the carrier’s offspringOffspring can be carrier or express the gene in the phenotype (e.g. when unexpressed gene is inherited by both parents)
17HeritabilityStatistical term that indicates what portion of the variation in a particular trait within a particular population is inherited.Example: 90% of the height differences among children of the same age is genetic.Environment can affect the expression of inherited genes.
18Genetic Problems Chromosomal Abnormalities Down Syndrome (Trisomy-21) Three copies of chromosome 21Specific facial characteristics (thick tongue, round face, slanted eyes)Hearing losses, heart abnormalities, muscle weakness, short statureSlow to develop languageAccelerated aging (cataracts, dementia, certain forms of cancer common at age 40)
19Genetic Problems Abnormalities of the Sex Chromosomes Turner Syndrome (X only):Unusually short, underdeveloped female organs, infertileSlow to developProblems in spatial understandingKlinefelter Syndrome (XXY):Symptoms include learning problems and infertilityBoy’s penis does not grow during puberty and fat accumulates around the breast areaSometimes not recognized until adulthood
20Genetic Problems Gene Disorders Dominant Disorders Half of the offspring of parents with a dominant disorder will have the disorder.Most dominant disorders begin in adulthood (fatal dominant childhood conditions cannot be passed on).Many dominant disorders have relatively mild or variable symptoms.Tourette syndromeSome who inherit the dominant gene exhibit uncontrollable tics and explosive outburstsMost have milder, barely noticeable symptoms
21Genetic Problems Recessive Disorders Millions of different types, lethal conditions are rareSickle-cell traitOffers some protection against malariaAfrican carriers are more likely than non-carriers to surviveCystic fibrosisMore common among people with northern European ancestorsCarriers may have been protected against cholera
23Sex-Linked Conditions All X-linked conditions are more common in boys; girls are likely to be protected by their second XFragile X SyndromeMost common form of inherited mental retardationAdditional symptoms include muscle weakness, shyness, and poor social skillsHemophiliaBlood clotting is inhibitedBlood transfusions can save children’s livesColor blindnessMost common sex-linked conditionOften passed on because it is not debilitating
25Advising Prospective Parents Genetic CounselingConsultation and testing by trained professionalsEnables prospective parents to learn about their genetic heritage, including harmful conditions that may be passed on to their offspringEthical GuidelinesTest results are kept confidentialDecisions regarding sterilization, adoption, abortion, or carrying a pregnancy to term are made by the clients
27Presenting the Facts Potential genetic counseling issues Prospective parents must base some decisions on oddsTests often reveal that more tests are neededFalse positives and false negativesTrue positives may cause additional stress
28PKU: A Success Story Phenylketonuria (PKU) Recessive condition Results in inability to metabolize phenylalanine (amino acid found in many foods)Buildup of phenylalanine causes brain damage, progressive mental retardation, and other symptomsEarly testing and a special diet usually results in normal development
29From Zygote to Newborn Three main periods of prenatal development Germinal Period (first two weeks after conception): rapid cell division and beginning of cell differentiationEmbryonic Period (3rd through 8th week): basic forms of all body structures developFetal Period (9th week until birth): fetus grows in size and matures in functioning
30The Germinal PeriodZygote begins duplication and division within hours of conceptionDevelopment of the placentaOrgan that surrounds the developing embryo and is attached to the wall of the uterusSustains life via the umbilical chord (nourishes organism and carries waste products away)Implantation (about 10 days after conception)Developing organism burrows into the placenta that lines the uterusOrganism grows rapidlyPregnancy can be detected due to new chemicals in the mother’s urine
33The Embryonic Period Embryo Developing human organism from about the 3rd through the 8th week after conceptionBegins when the primitive streak appears down the middle of the cell massPrimitive streak becomes the neural tube and later forms the brain and spine of the CNSHead takes shapeEyes, ears, nose, and mouth formHeart begins to pulsateExtremities develop and webbed fingers and toes separate
35The Fetal PeriodFetusDeveloping human organism from the start of the 9th week after conception until birthGenitals form and sex hormones cause differences in fetal brain organizationCephalocaudal and proximodistal growthHeartbeat detectable via stethoscopeAll body parts and systems complete prenatal developmentCortex is not fully mature at birth (e.g. prefrontal lobes)Brain at birth is far bigger than any other part of the baby
36The Fetal Period Age of viability Age at which a preterm newborn may survive outside the mother’s uterus if medical care is availableAbout 22 weeks after conceptionBrain is able to regulate basic body functions (e.g. breathing)Chances of survival increase with each day after the 22-week mark
38BirthFetal brain signals the release of hormones to trigger the female’s uterine musclesLabor beginsAverage duration for firstborn babies: 12 hoursQuicker labor for later-born babiesApgar scaleQuick assessment of newborn’s heart rate, breathing, muscle tone, color, and reflexesCompleted twice (1 minute and 5 minutes after birth)Score of 0, 1, or 2 in each categoryDesired score: 7 or above
40Traditional and Modern Birthing Practices Home birthsHospital birthsDoulaWoman who helps with labor, delivery, breast-feeding, and newborn careMay be related to lower rate of cesarean sections
41Cesarean Section (C-Section) Surgical birthFetus can be removed quicklyRates and reasons for c-sections vary greatlyLower rates in poorer countries (emergencies)Higher rates in richer countries (planned for the convenience of mother and/or obstetrician)1/3 of births in the United StatesLess trauma for the newborn but slower recovery for the motherSubsequent cesarean deliveries may be necessary
43Medical InterventionInfant mortality has decreased due to better medical care1900: 5%Today: <1 in 200Childbirth has become safer for mothersDeath rate in poorest nations: 1 in 20 womenExcessive medical care also has disadvantagesIncrease in unnecessary c-sections is associated with higher rate of low-birth weight babies
44Low Birthweight Low birthweight (LBW) Very low birthweight (VLBW) Less than 2,500 grams (5½ pounds) at birthUnited StatesSteady increase in LBW over the past 25 years8% of newborns are seriously underweightMore susceptible to teratogens, higher birth risks, lower survival rateVery low birthweight (VLBW)Under 1,500 grams (3 pounds, 5 ounces) at birthExtremely low birthweightUnder 1,000 grams (2 pounds, 3 ounces) at birth
46Preterm or Slow Growing? Birth that occurs at 35 or fewer weeks after conceptionUsually associated with low birthweightSmall for gestational age (SGA)Birthweight is significantly lower than expected, given the time since conceptionSuggests impairment throughout prenatal development and serious problems
47Causes of Low Birthweight Genetic factorsMaternal illnessExhaustionInfectionMalnutritionDrug useMultiple births
48Mothers, Fathers, and a Good Start The Father’s RoleSupportive father helps mother stay healthyFather can decrease or increase mother’s stress (affects fetus)Most fathers are helpful to their pregnant wivesTwo way street: Pregnant mothers should support, involve, and encourage fathers
49The Importance of Close Contact Birth complications can have lingering impact on later lifeMothers and fathers should help with early caregiving if newborn must stay in the hospitalKangaroo careChild-care technique in which the mother of a low-birthweight infant holds the baby between her breastsAllows baby to hear mother’s heartbeat and feel her body heatResearch confirms beneficial effects
50Postpartum Depression Sadness and inadequacy felt by 8-15% of new mothers in the days and weeks after giving birthSymptoms range from baby blues to postpartum psychosisDepressed mothers find baby care burdensome and may think about mistreating the infantPaternal involvement can have beneficial effectSome fathers are depressed themselvesCauses for Postpartum Depression vary
51Bonding Parent-Infant Bond The strong, loving connection that forms as parents hold, examine, and feed the newbornEarly skin-to-skin contact is not essentialCross-fostering in monkeysNewborns are removed from their mothers and raised by another female or maleStrong and beneficial relationship sometimes develops
52Nature, Nurture, and the Phenotype Four general research conclusionsGenes affect every aspect of human behaviorNongenetic influences begin at conception and continue lifelong, sometimes altering genetic instructionsMost environmental influences on children raised in the same home are NOT shared, partly because parents treat each child differentlyChildren , adolescents, and adults “niche-pick,” choosing environments that are compatible with their genetic inheritance
53Nearsightedness or Myopia “High” (more severe) and “low” (less severe) nearsightednessLow nearsightedness runs in families and is associated with minor variations in the Pax6 geneEnvironment also plays a roleIncrease in nearsightedness among East Asian schoolchildrenIncreased schoolwork may have caused nearsightedness in children with a Pax6 allelle
54Alcoholism Alcoholism probably has a genetic basis Genes can cause an overpowering addictive pull in some peopleEnvironmental conditions can modify the genetic effectsNature and nurture must combine to create an alcoholicFetal Alcohol Syndrome (FAS)A cluster of birth defects that may occur in the child of a woman who drinks alcohol while pregnantIncludes abnormal facial characteristics, slow physical growth, and retarded mental development
55Prenatal TeratogensSubstances and conditions that can impair prenatal development and result in birth defects or even deathNot all teratogens can be avoidedStructural abnormalities are obvious at birthBehavioral teratogensAffect the child’s developing brainCan cause developmental retardation, hyperactivity, and learning disabilitiesEffects do not become evident for months or years
57Significant Factors Genetic Vulnerability Some zygotes carry genes that make them vulnerableCertain genes increase likelihood of cleft lip in Japanese peopleSome women do not metabolize folic acid wellIncreases rates of neural-tube defects (e.g. spina bifida)Folic acid was added to many foods in the United States and Canada and rates have decreased
58Significant Factors Timing of Exposure Critical period: time when a body part developsFirst two months for structural abnormalitiesOften before woman knows she is pregnantTime when most spontaneous abortions occurSensitive period: time when teratogens can interfere with recent growth
60Significant Factors Amount of Exposure Threshold effect: Certain teratogens are relatively harmless until exposure reaches a certain levelBisphenol A (BPA)Chemical compound used to make clear plasticSmall doses are harmless but threshold for humans is unknownPregnant mothers should avoid plastic containers and dishwarePrescription drugsVitamin AHigh doses can be harmful
61Resolving Uncertainties Pregnancy does not have to be an anxious timeGood prenatal care canteach women what they can do to have healthy babiessave livesreassure parents that all is well