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 on 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 selected from the mother’s 46-one 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
8Mechanisms of Heredity The complete set of inherited traits are called a genotypeHow the traits are expressed is called a phenotype-combined effects of genotype ond environmentalinfluences
9AllelesCharacteristics are determined my the interaction of genes on the two chromosomes in a pairEach chromosome of a pair contains on parent’s contribution to a specific traitWhen genes are the same, they are call homozygousWhen different, they are called hterozygous
10Alleles Homozygous Alleles -When alleles are the same, both parents havecontributed similar genes for a traitHeterozygous Alleles-The parents have contributed different versions ofthe trait
11Genetic 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, Turner’s Syndrome andKlinefelter’s Syndrome
12Heredity, Environment and Development Behavioral Genetics-The study of the inheritance of behavioral andpsychological traits
13Polygenetic Inheritance When many genes affect the phenotype of a trait-Many psychological and behavioralcharacteristics are polygenetic and areimpossible to trace to a single gene.
14TwinsDizygotic (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
15Twins 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 identical
16Path 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
17From 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?
18Periods of Prenatal Development Period of Zygote (Weeks 1-2)-After fertilization, the zygote travels down thefallopian tube and is implanted in the uterinewallPeriod of the Embryo (Weeks 2-8)-Body structures, internal organs, and the threelayers of the embryo (ectoderm, mesoderm, andendoderm ) develop-The amniotic sac fills with fluid and the umbilicalcord connects the embryo to the placenta
20Periods of Prenatal Development Period of the Fetus (Week 9-Birth)Week 9- Differentiation of the ovaries and testesWeek 12- Circulatory system begins ot functionWeek 16- Movement felt by the motherWeek 32- Age of viability
21Conception in the 21st Century -In Vitro fertilization-inserting sperm directly into the Fallopiantubes-injecting sperm directly into the egg
22Principles of Growth Cephalocaudal Principle -Growth from head to spineProximodistal Principle-Growth from areas close to the body to farthestfrom body
23Influences 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?
24General Risk Factors Nutrition Stress -Inadequate maternal nutrition may result inpremature birth and low birth weight-Lack of folic acid may increase risk for spinabifidaStress-Studies show extreme maternal stress is associatedwith low birth weight and premature births
25General 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
26Teratogens: Drugs Known harmful agents include: -Alcohol, aspirin, caffeine, nicotineFetal Alcohol Syndrome-Results from overuse of alcohol during pregnancy-Children with FAS may have mental retardation,facial deformities, and heart defects
27Teratogens: Diseases AIDS, Cytomegalovirus, Genital Herpes, Rubella (German Measles), Syphilis-Effects include:-neurological disorders-deafness-blindness-mental disability-damage to bones, eyes, ears, or heart
28Teratogens: Environmental Hazards Lead, Mercury, PCB’s, X-Rays-Effects may include:-mental disability-retarded growth-cerebral palsy-impaired memory and verbal skill-leukemia
29How Teratogens Influence Prenatal Development The effect of the teratogen depends upon the genotype of the organismThe impact of teratogens change 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
30Prenatal Diagnosis and Treatment Genetic Counseling-Helps to assess the chances of inherent disordersPrenatal Diagnosis-Ultrasound-Amniocentesis-Chorionic Villus Sampling
32Prenatal Diagnosis and Treatment Fetal Medicine-Administering medicine to the fetus-Fetal surgury to correct spina bifida andcirculatory problems-Genetic engineering involves replacing defectivegenes with synthetic normal genes
33Labor 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 dveloped and least developed countries?
34Stage of Labor Stage 1 -last 12-24 hours for the first birth -contractions and enlargement of the cervix toapproximately 10 centimetersStage 2-actual birth of the baby-lasts about an hourStage 3-lasts a few minutes-expulsion of the placenta
36Approaches 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
37Birthing 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
38Labor 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 have low birthweight-weighing less than 3.3 pounds have very low birth-weighing 2.2 pounds or less is call extremely low birth
39Infant 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