Presentation on theme: "Biological foundations: Heredity, Prenatal development and birth"— Presentation transcript:
1Biological foundations: Heredity, Prenatal development and birth Chapter Two
2In The Beginning Learning Objectives What are chromosomes and genes?How do they carry hereditary information from one generation to the next?What are common problems involving chromosomes and what are the consequences?How is a child’s heredity influenced by the environment in which they grow?
3Mechanisms of Heredity Human eggs contain 23 chromosomes (threadlike structures in the nucleus) selected from the mother’s 46one chromosome is selected from each of the 23pairsHuman sperm contains 23 chromosomes selectedfrom the father’s 46
4Mechanisms of Heredity The human egg and sperm unite resulting in a zygote-contains a complete set of 46 chromosomes- first 22 chromosomes are called autosomes-23rd pair determines the gender of the child andis called the sex chromosomes-the 46 chromosomes contain around 30,000genes
5Mechanisms of Heredity The 23rd Pair of Chromosomes-Males carry XY Chromosomes-X from mother and Y from father-Females carry XX chromosomes-X from mother and X from father
6Mechanisms of Heredity Each chromosome actually consists of one molecule of deoxyribonucleic acid. (DNA)To understand the structure of DNA, imagine:Four different chemical compounds placed on two stringsWhen two compounds (adenine, thymine, guanine, cytosine)line up exactly they make chemical compounds which are like a secrete codeEach group of compounds that provides a specific set of biochemical instructions is called a geneThe strings wrap around each other to create a double helix
9Mechanisms of Heredity Each group of compounds that provide a set of instructions is a gene (functional unit of heredity)Fewer than 1% of genes cause differences between peopleAlleles – different forms ofgenes i.e. sickle cells (recessive) and normal red cells (dominant)The complete set of genes that make up a person’s heredity is called a genotypePhenotype - combinedeffect of genotype andenvironmental influences
10AllelesCharacteristics are determined my the interaction of genes on the two chromosomes in a pairEach chromosome of a pair contains one parent’s contribution to a specific traitWhen genes (alleles)are the same, they are call homozygousWhen different alleles, they are called heterozygous
11Alleles Homozygous Alleles -When alleles are the same, both parents havecontributed similar genes for a traitHeterozygous Alleles-The parents have contributed different versions ofthe traitDominant alleles- instructions followedRecessive alleles- instructions ignored
12AllelesIncomplete dominance results when one allele does not dominate another completely. The result is a trait as a sickle cell trait. In this instance the person may have tempory problems only when seriously short of O2 as when at high altitudes or when exercising.
13Some Common Phenotypes Associated with Single Pair Genes Dominant PhenotypeRecessive PhenotypeCurly HairStraight HairNormal HairPatterns of BaldnessDark HairBlond HairCheek dimplesNo dimplesNormal HearingSome type of deafnessNormal VisionNearsightednessFarsightednessNormal color visionGreen red blindnessType A or B bloodType O bloodRh positive bloodRh negative blood
14Genetic DisordersInherited disorders involve dominant or recessive alleles-Sickle-Cell Disease, PKU and Huntington’s DiseaseExtra, missing or damaged chromosomes result inabnormalities of development-Down’s Syndrome (extra 21st chromosome provided by the egg), Turner’s Syndrome (X),andKlinefelter’s Syndrome (XXY)
15Heredity, Environment and Development Behavioral GeneticsThe study of the inheritance of behavioral andpsychological traits. Characteristics are not either/or but are complex. Includes intelligence and personality.
16Polygenetic Inheritance When many genes affect the phenotype of a traitMany psychological and behavioral characteristics are polygenetic and areimpossible to trace to a single gene.Aa, Bb, Cc, Dd 4 genes can produce multiple genotypes and phenotypes. Makes study difficult. Studies easier on twins and adopted persons. Environment also plays a role. Conclusions depend on many different studies and study methods.Now can study DNA markers.
17TwinsDizygotic (fraternal) twins come from two different eggs fertilized by two different spermMonozygotic (identical) twins come from the union ofone egg and one sperm that splits in two soon after conception
18Twins Fraternal twins -share much of the same experience and environment- have no more genetic similarity than other siblingsIdentical twins-share much the same experience-genetically identicalAdopted siblings have different experiences and some genetic similarity
19Path From Genes to Behavior Genes impact on behavior depends on the environment-reaction rangeHeredity and environment interact throughout developmentGenes can influence the kind of environment to which a person is exposedEnvironment influences typically make children within a family different
20Path From Genes to Behavior Genes can influence the kind of environment to which one is exposed.Niche-picking (a bright child will seek like friends etc.) – deliberately seeking environments that fir one’s heredityEnvironmental influences typically make children within a family different due to nonshared environmental influences.
21Path From Genes to Behavior Epigenesis – interplay between genes and multiple levels of the environment from cellular level to cultureHeritability coefficient – estimates the extent to which differences between people reflect heredity. Intelligence has a coefficient of 0.5 applied to specific groups of people in a particular environment. 50% of the differences in intelligence between people is due to heredity.
22From Conception to Birth Learning Objectives What happens to a fertilized egg in the first two weeks after conception?When do structures and internal organs emerge in prenatal development?When do body systems begin to function well enough to support life?
23Periods of Prenatal Development Period of Zygote (Weeks 1-2)From fertilization, the zygote travels down thefallopian tube dividing every 12 hours, to the time of implantation in the uterine wall.Germ disk – cluster of cells in the zygote that become the babyPeriod of the Embryo (Weeks 2-8)Body structures, internal organs, and the three layers of the embryo (ectoderm - hair, outer layer of skin, nervous system, mesoderm-muscles, bones, circulatory system, and endoderm- digestive system, lungs ) developThe amniotic sac fills with fluid and the umbilical cord connects the embryo to the placenta
24Periods of Prenatal Development Amnion – sac containing embryo and amniotic fluidUmbilical cord houses vassals that exchange nutrients and wastes with mother’s bloodGrowth occurs by the cephalocaudal and proximodistal principles
25The period of the zygote spans 14 days that begin with fertilization of the egg in the fallopian tubes and end with implantation of the fertilized egg in the wall of the uterus.
27Periods of Prenatal Development Period of the Fetus (Week 9-38 weeks Birth)Week 9- Differentiation of the ovaries and testes, cartilage becomes boneWeek 12- Circulatory system begins to function, heart has been beating almost two monthsWeek 16- Movement felt by the motherWeek Age of viability
28Periods of Prenatal Development Fetuses move – more active fetuses are more likely to be unhappy difficult babiesDiscern flavorsHearRemember after birth
29The baby-to-be becomes much larger during the period of the fetus and its bodily systems start to work.
30Conception in the 21st Century -In Vitro fertilization-inserting sperm directly into the Fallopiantubes-injecting sperm directly into the eggInserting fertilized eggs into the wombSurrogate mothersPicking sperm donors - is this engenics (improving the human species by only allowing certain people to mate)
31Principles of Growth Cephalocaudal Principle -Growth from head to spineProximodistal Principle-Growth from areas close to the body to farthestfrom body
32Influences of Prenatal Development Learning Objectives How is prenatal development influence by a pregnant woman’s age, her nutrition, and the stress she experiences while pregnant?How do diseases, drugs, and environmental hazards sometimes affect prenatal development?What general principles affect the ways that prenatal development can be harmed?How can prenatal development be monitored? Can abnormal prenatal development be corrected?
33General Risk Factors Nutrition Stress -Inadequate maternal nutrition may result in premature birth and low birth weight. Need to increase caloric intake by 10-20% and gain25 – 35 lbs. Take additional protein, vitamins, minerals.Lack of folic acid during the first month may increase risk for spina bifidaStress-Studies show extreme maternal stress is associatedwith low birth weight and premature births
34General Risk Factors Mother’ Age -Older mothers are more likely to have difficultygetting pregnant, miscarriages, and stillbirths-Nearly 50% of pregnancies among women in their40’s and 50’s result in miscarriages
35TeratogensTeratogen = an agent that causes abnormal prenatal development3 categories:DrugsDiseaseEnvironmental hazards
36Teratogens: Drugs Known harmful agents include: Alcohol - FAS, Aspirin – Defects in intelligence,attention, motor skills,Caffeine – rotated growth irritabilityNicotine – growth and cognitive impairmentsMarijuana – low birth rate, less motor controlCocaine, heroin – retarded growth, irritabilityFetal Alcohol Syndrome-Results from overuse of alcohol during pregnancy-Children with FAS may have mental retardation,facial deformities, and heart defects, retarded growthLeading caues of developmental disabilities in US
37Teratogens: DiseasesAIDS, Cytomegalovirus, Rubella (German Measles), Syphilis attack embryo of fetus directly, Chicken Pox, Chlamydia, Genital Herpes, ToxoplasmosisAids and herpes attack as fetus passes through birth canal-Effects include:-neurological disorders-deafness-blindness-mental disability-damage to bones, eyes, ears, or heart-frequent infections-death-prematurity- miscarriage-encephalitis-damage to eyes, teeth, bones
38Teratogens: Environmental Hazards Lead, Mercury, PCB’s, X-Rays-Effects may include:-mental disability-retarded growth-cerebral palsy-impaired memory and verbal skill-leukemia
39How Teratogens Influence Prenatal Development The effect of the teratogen depends upon the genotype of the organismThe impact of teratogens changes over the course of prenatal developmentEach teratogen affects a specific aspect of prenatal developmentThe impact of teratogens depends on the dosageDamage from teratogens in not always evident at birth, but may appear later in life
40Prenatal Diagnosis and Treatment Genetic CounselingHelps to assess the chances of inherited disordersPrenatal DiagnosisUltrasound – sound waves used to generate a picture of the developing fetus – 4yh or 5yh week. Determine position ,sex, abnormalities, numberAmniocentesis – needle inserted through the abdominal wall into the uterus to obtain a sample of amniotic fluid, determine genotype, danger miscarriageChorionic Villus Sampling – sample of fetal cells obtained from a part of the placenta ,earlier 9-12 weeks, than amniocentesis, danger miscarriage
42Prenatal Diagnosis and Treatment Fetal Medicine-Administering medicine to the fetus,ie.for hypothyroidism, adrenal hyperplasia, excess androgens-Fetal surgury to correct spina bifida andcirculatory problems-Genetic engineering involves replacing defectivegenes with synthetic normal genes
43Labor and Delivery Learning Objectives What are the different phases of labor and delivery?What are the natural ways of coping with the pain of childbirth? Is childbirth at home safe?What adjustments do parents face after a baby’s birth?What contributes to infant mortality in the developed and least developed countries?
44Stage of Labor Stage 1 -last 12-24 hours for the first birth -contractions and enlargement of the cervix toapproximately 10 centimeters,4-6 hrs for subsequent deliveriesStage 2-actual birth of the baby-lasts about an hour first birth , 2omin subsequentStage 3-lasts a few minutes-expulsion of the placenta
46Approaches to Childbirth Childbirth classes-Explains what happens during pregnancy anddelivery-Teaches techniques to manage the pain ofchildbirth-natural methods, relaxation and coaching-Studies show that mothers who attend childbirthclasses typically use less medication
47Birthing Alternatives Home Births-less expensive-parents have more control over the conditions-birth problems are no more common at home thenat the hospital when pregnancy has beenproblem-freeBirthing Centers-more home-like then hospitals-clinic setting independent of hospital
48Adjusting to Parenthood Physical changes in the woman – breasts producing milk, levels of female hormones drop,Adjustments to infants sleep-wake cycle and neeedsFather often suffers reduced attentionPostpartum depression can last years affecting the child’s development
49Labor and Delivery: Birth Complications Cephalopelvic Disproportion – baby’s head is larger than the pelvis; baby can’t pass through the birth canalIrregular position – shoulder presentation: baby is lying crosswise in the uterus and the shoulder appears first; breech presentation: buttocks appear firstPreeclampsia – a pregnant woman has high BP, protein in her urine, and swelling in her extremities due to fluid retentionProlapsed Umbilical Cord – the umbilical cord precedes the baby through the birth canal and is squeezed shut, cutting off oxygen to the baby (hypoxia) leading to mental retardation or death
50Labor and Delivery Birth Complications Hypoxia, or inadequate blood and oxygen to the babyComplications may result in a cesarean section (C-sectionBirths before the 36th week are called premature or preterm-weighing less the 5.5 pounds (2500 grams) have low birthweight-weighing less than 3.3 pounds 1500 grams) have very low birth weight-weighing 2.2 pounds (1000 grams) or less is call extremely low birth weight
51Labor and Delivery Birth Complications Birth complications can lead to aggression, violence or schizophrenia in the childHigher risk for children born into family adversity and/or povertyExcellent health care needed during pregnancySupportive environment needed throughout childhood
52Infant MortalityInfant mortality is the number of infants out of 1,000 births that die before the age of 1 year-U.S. mortality rate is just under 1%, or 7 of 1,000-15 industrialized nations have lower infantmortality than the U.S.Possible factors include:-low birth weight-lack of free or inexpensive prenatal care-fewer paid leave of absences for pregnant women
53Infant MortalityIn Afghanistan 1in 6 babies die within the first year, has the highest infant mortality rate in the worldIn Czech Republic, Iceland, Finland, Japan odds are 1 in 300 of dying before first birthday13 developed countries have lower infant mortality rates than US mainly because of lacking medical care, due to lack of insurance. Other developed countries have free or low cost medical care.If US reduced it’s mortality rate to 4% AS IN Europe, 8000 babies would not die annually.