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Forming a New Life

Forming a New Life. OUTLINE. Conceiving new life Mechanisms of Heredity Nature & Nurture Prenatal Development Monitoring/Promoting Prenatal Development. Mechanisms of heredity. Genes: basic functional unit of heredity, genes are made up of DNA

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Forming a New Life

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  1. Forming a New Life

  2. OUTLINE • Conceiving new life • Mechanisms of Heredity • Nature & Nurture • Prenatal Development • Monitoring/Promoting Prenatal Development

  3. Mechanisms of heredity • Genes: basic functional unit of heredity, genes are made up of DNA • Each gene is located by function on a definite position on a particular chromosome • Human Genome: complete sequence of genes in the human body • 23 from mother, 23 from father (22 autsome, 1 pair of sex chromosome)

  4. Mechanisms of reproductive cells • Gametes: sperm (m) and ovum (f) • contain 23 chromosomes • form through meiosis • germ cells pair up • chromosomes replicate • crossing-over occurs • chromosomes separate and cell divides

  5. Genes • Genes are contained on chromosomes • Chromosomes are made up of DNA • Most genes are universal • basic human abilities: language, walking, running, social communication • Some genes are diverse • height, weight, activity levels, eagerness to learn, emotionality, etc. • Genetic expression affected by time, environment

  6. Conception Fertilization: union of ovum & sperm = zygote which then duplicates through cell division • Sperm fertilizes ovum • zygote has 23 + 23 chromosomes • sexdetermined on 23rd pair • XX; XY • Cells continue to divide • 2 separate cell clusters: monozygotic twins • 2 ova + 2 sperm: dizygotic twins Multiple births: fertilization of 2 ovum or splitting of 1 fertilized ovum Dizygotic (fraternal) Monozygotic (identical)

  7. Patterns of genetic inheritance • Dominant/recessive inheritance • Gene pairs include two alleles • provide instructions for physical characteristics • dominant and recessive genes • codominant genes • most characteristics: polygenic inheritance • Allele (alternate forms of a gene) • Homozygous • Heterozygous • Gene pairs include two alleles • provide instructions for physical characteristics • dominant and recessive genes • codominant genes • most characteristics: polygenic inheritance Polygenic/multifactorial transmission along with dominant inheritance explain why a phenotype is not always an exact expression of genotype

  8. Epigenetic Framework & Genetic/Chromosomal Abnormalities • Controls the functions of particular genes and is often affected by environmental factors • Birth defects/diseases: inheritance, mutations, genome imprinting and chromosomal abnormalities • Genetic counseling • Genetic testing

  9. Chromosomal Abnormalities • Chromosomal abnormalities • extra chromosome (e.g., Down syndrome) • missing or wrongly formed chromosome • 1 in 150 births • Single-gene defects • inherited from one or both parents • Other problems • defective gene (e.g., Fragile X syndrome) • problem with multiple genes (e.g., Spina bifida)

  10. Awakening the genetics • Occurs at different times in the lifespan • Some characteristics are canalized • canalization – tight genetic control • basic motor skills: crawling, sitting, walking • Others more influenced by environment • not canalized: reading, writing, math, social skills • Some characteristics awaken during sensitive periods • perception, language, close bond to caregiver

  11. Nature & Nurture…revisited….again

  12. How do we study the influences of heredity and environment; do they work together? • Phenotype for normal traits = subject to a complex network of hereditary & environmental forces • Behavioral genetics: quantitative mode of inquiry (statistics) • Heritability • Studies

  13. Heredity & Environment working together • Passive gene-environment relation • parents’ genetic tendencies influence child’s environment • parents’ choice • Active gene-environment relation • child’s genetic characteristics influences his/her environment • child’s choice • Evocative gene-environment relation • child’s genetic characteristics elicit responses from environment • someone’s response to the child; not the child’s choice

  14. How the interactions function

  15. Familial Differences • Siblings tend to be more different than alike • Genetic differences may lead to children needing/seeking different forms of stimulation even within a similar environment • Nonshared environmental effects (NEE) • Heredity accounts for most of the similarity and NEE accounts for most of the difference

  16. Characteristics influenced by heredity and environment • Physical/Psychological Traits • Obesity • Intelligence • Personality • Temperament • Psychopathology

  17. Prenatal Development:3 Stages • Prenatal Development: 3 stages of gestation • Germinal • Embryonic • Fetal

  18. Development post conception • 3 Phases of Prenatal Growth • zygote • conception – 2 weeks post • embryo • 2 weeks – 8 weeks • fetus • 8 weeks – birth

  19. Germinal period: • First 14 days post fertilization • Ends w/ implantation • 66% failure rate! • Cell divides many times 1, 2, 4, 16, 256, 65536….. • Cannot detect pregnancy here.

  20. Zygote • Begins at conception • ovum prevents additional sperm from entering • chromosomes combine to form zygote • Mitosis occurs • Attaches to uterine wall (~ 16 cells) • Separates into embryo & placenta • Releases hormones telling body to cease menstruation • Cells begin to specialize • nervous system, brain

  21. Embryo • Life support system formed • placenta grows larger, stronger, and more refined • umbilical cord develops • provides food, liquid, oxygen; removes waste • secretes hormones to sustain embryonic growth • Basic body structures develop • from top to bottom (head first, feet last) • from inside to outside • torso before limbs; internal organs • arms & legs before hands & feet • fingers and toes recognizable at 8 weeks

  22. Embryonic • Weeks 3 through 8 • Starts w/ __________________? (seepreviousslide- rhymes w/vimplantation) • Embryo receives nourishment- • (and other things see teratogens) • Basic body structures develop. • At 8 weeks weighs 1 gram (three paperclips) and is about 1 inch. FYI: ontogeny recapitulates phylogeny

  23. Fetal period Week 9 to birth. Very rapid development- 1g to 3000 g 3rd month: • sex organs develop • Major systems are all present • First movement 4th, 5th, and 6th months (middle three) • Preparing to survive • Digestive, heart, and respiratory systems develop • Getting fat!

  24. Age of viability ~ 22 weeks (beginning of fourth month) • Fetus can survive in hospital (intensive care). Brain function is vital: • Lower brain areas produce “automatic” functions • Breathing- • Sucking Body weight is also vital

  25. Fetus • Third month • head is large but growing slowly • eyes move into place; increasingly human-looking • genitalia form • reflex and muscular movement (although not felt) • Fourth month • rapid growth in length (height) • slow weight increase • hair growth on head and eyebrows • Fifth month • rapid growth in length (height) continues • fine hair growth covers body • movement felt by motherSixth month (avg. weight 1 lb. 13 oz.) • skin red, wrinkled; body lean; fingernails evident • development of respiratory & central nervous system • Seventh month (avg. weight 2 lb. 14 oz.) • eyes open; eyelashes and toenails form • body fills out • Eighth month (avg. weight 4 lb. 10 oz.) • skin becomes pink, smooth; fat grows beneath skin • testes descend (in males) • Brain development • preparation for reflexes • sucking, swallowing, looking away from light • activates circuits for sensing stimulation • can hear/remember music • can taste/recognize flavors

  26. T/F Germinal development requires nutrients to be constantly delivered via the mother. F Embryonic development begins at implantation. T Embryonic development is all about getting bigger, not about making new stuff. F The Age of viability refers to the minimum amount of gestation (prenatal development) required for survival outside the womb. T It depends on brain development but not on organ development. F Both? T Also technology & the “medical context?” T

  27. Environmental Influences affect prenatal development • Effect contingent on timing/intensity of event • Important environmental influences (effect sperm and egg) • Nutrition • Smoking alcohol/drug intake • Transmission of disease • Stress • Maternal age • External environmental hazards • Chemicals • Radiation

  28. Brain development: (More in Ch 5) Brains grow very rapidly: Neurons are: • being produced • growing axons and dendrites • forming functional connections. Synaptogenesis: Synapse creation. • “Use it or lose it” • Neurons that form connections are nourished and live-

  29. Supporting Healthy Development • Starts before conception • Watch diet, take approved vitamin supplements • Exercise • Avoid alcohol and drugs (includes OTC meds) • See genetic counselor AVOIDING TERATOGENS • Potentially harmful substances • prescription or non-prescription drugs • infectious agents, e.g., rubella, syphilis, HIV • environmental chemicals, e.g., lead • maternal stress • Effects depend on amount, timing, genetic makeup of mother & child • embryonic: development of body • fetal: development of brain • Ultrasonography • CVS (Chorionic Villus Sampling) • 10-12 weeks • high-risk pregnancies • identifies chromosomal abnormalities, X-linked disorders, some blood diseases • Amniocentesis • 13-18 weeks • identifies neural tube defects & chromosomal abnormalities

  30. Risk reduction “despite many dangers- the vast majority of newborns are healthy” Most hazards can be avoided or treated.

  31. Teratogens: • Substances or conditions that can cause prenatal damage. • Some can alter brain development. Risk analysis: • Evaluating the likelihood that a teratogen will cause damage. • how likely is it that teratogen “x” will damage fetus “y”

  32. X3 factors: 1. Timing: see chart p. 99 • Early damage causes “downstream” effects. • Some systems develop in sequence- • AB  C  D  E…. • Damage at “C” can damage D  E  F…. Critical periods: • The time when a “part” is most vulnerable to damage. Note: usually at a time of rapid cellular division/growth.

  33. X3 factors (cont): 2. Amount: • How much of a teratogen is present. • Threshold effect: • level at which a substance becomes a toxin. • E.g. Vitamin A • Interaction effect: • Some teratogens when combined become more toxic (e.g. alcohol + tobacco) • Combinations can increase toxicity- decrease threshold!

  34. X3 factors (cont.): 3. Genes: Genes affect vulnerability.

  35. Prenatal Care • Techniques to assess fetus health, is the unborn baby developing normally? • Good care can lead to detection of defect or disorder and may help reduce these events as well as enhance wellbeing, quality of life of mother, infant, and family • Disparities in prenatal care • Need for preconception care

  36. Birthing • Triggered by mother’s hormonal changes & maturation of fetus • Braxton Hicks contractions begin • Fetus settles in head-downward position • Caesarean delivery if breech or sideways • Just before labor: • baby descends into pelvis • mother may experience • rush of energy • weight loss (1 to 4 pounds) • vaginal secretions • difficulty sleeping • First stage • regular contractions • widening of cervix • pelvis and back pain • Second stage • cervix dilated (10 cm) • baby proceeds down birth canal • Third stage • afterbirth expelled by uterus (placenta & fetal membranes) • Fourth stage • mother’s body readjusts • Induced labor using Pitocin • Analgesics • epidural analgesia (spinal injection) • Anesthetics • Opioids/narcotics • Caesarean delivery • in U.S., currently 30% • Medical personnel do their best to accommodate women’s cultural practices

  37. Latest ResearchAmerican Society for Reproductive Medicine (ASRM). Age and Fertility: A Guide for Patients. ASRM, Birmingham, AL, 2003, accessed 2/5/09 Does age affect fertility? Women usually have some decrease in fertility starting in their early 30s. It often takes a woman in her mid-30s or older longer to conceive than a younger woman. Men also may have some decrease in fertility starting in their late 30s (2). • Women over age 35 may be less fertile than younger women because they tend to ovulate (release an egg from the ovaries) less frequently. Certain health conditions that are more common in this age group also may interfere with conception. These include (3): • Endometriosis (a condition in which tissue attaches to the ovaries or fallopian tubes) • Blocked fallopian tubes (sometimes resulting from past infections) • Fibroids (non-cancerous growths in the uterus) • A woman over age 35 should consult her health care provider if she has not conceived after 6 months of trying. Studies suggest that about one-third of women between 35 and 39 and about half of those over age 40 have fertility problems (4). Many fertility problems can be treated successfully. • While women over age 35 may have more difficulty conceiving, they also have a greater chance of having twins (5). The chances of having twins increases naturally with age. Women over 35 also are more likely to undergo fertility treatment, which also increases the chance of twins (as well as triplets and other multiples).

  38. Latest ResearchAmerican Society for Reproductive Medicine (ASRM). Age and Fertility: A Guide for Patients. ASRM, Birmingham, AL, 2003, accessed 2/5/09 Are women over age 35 at increased risk of having a baby with a birth defect? A woman's risk of having a baby with certain birth defects involving chromosomes (the structures in cells that contain genes) increases with age. Down syndrome is the most common chromosomal birth defect. Affected children have varying degrees of intellectual disabilities and physical birth defects. A woman's risk of having a baby with Down syndrome is (1): • At age 25, 1 in 1,250 • At age 30, 1 in 1,000 • At age 35, 1 in 400 • At age 40, 1 in 100 • At 45, 1 in 30 • At 49, a 1 in 10 • The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women, regardless of age, be offered a screening test for Down syndrome and certain other chromosomal birth defects (6). Screening tests are blood tests done in the first or second trimester, sometimes with a special ultrasound.  They help evaluate a woman's risk for having a baby with certain birth defects, but they cannot diagnose a birth defect.

  39. Risk & Care • Born early (“premature”) • before the end of week 37 • risk of breathing problems, anemia, brain hemorrhages, feeding problems, instability in temperature • Born small for date • possible neurological deficiencies, structural problems with body parts, difficulty with breathing & vision • often due to exposure to teratogens or chromosomal abnormalities • Reduce infant’s exposure to light and noise. • Regulate amount of handling of infant by medical staff. • Position baby to increase circulation. • Encourage parents to participate in care. • Inform parents about infant’s needs. • Arrange activities such as diapering & changing clothes to minimize interruptions to sleep and rest. • Encourage parents to cuddle and carry infant. • Swaddle baby, with hands placed near the mouth. • Massage baby. • Educate parents about caring for the child as he or she grows.

  40. Low Birthweight Low Birthweight (LBW) less than 5 1/2 lbs. grows too slowly or weighs less than normal more common than 10 years ago second most common cause of neonatal death Preterm Birth that occurs at less than 37 weeks gestational age. Timing of embryonic development begins with fertilization

  41. Small for Gestational Age (SGA) maternal illness maternal behavior cigarette smoking (25% of SGA births) most commonly defined as a weight below the 10th percentile for the gestational age maternal malnutrition poorly nourished before and during pregnancy underweight, under eating, and smoking tend to occur together Low Birthweight, cont.

  42. Kangaroo care Holding newborn against skin for at least an hour a day. • Decreases infant stress • Increases suckling • Increases immune response

  43. Assessment—Apgar scale five factors, score of 7 or better: normal score under 7: needs help breathing score under 4: needs urgent critical care (Appearance, Pulse, Grimace, Activity, Respiration) --each criterion scored on a 0-2 scale The Apgar score was devised in 1952 by the eponymous (namesake) Dr. Virginia Apgar as a simple and repeatable method to quickly and summarily assess the health of newborn children immediately after birth. Apgar was an anesthesiologist who developed the score in order to ascertain the effects of obstetric anesthesia on babies. The Newborn’s First Minutes

  44. Human Development

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