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Genetics and Prenatal Development

2. Genetics and Prenatal Development. Genetic Basics Building Blocks of Life. Chromosomes DNA Genes Genomes. Genetic Basics Expression of Traits. Genotype-The totality of an individual ’ s genes Phenotype-Actual Characteristics

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Genetics and Prenatal Development

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  1. 2 Genetics and Prenatal Development

  2. Genetic BasicsBuilding Blocks of Life • Chromosomes • DNA • Genes • Genomes

  3. Genetic BasicsExpression of Traits • Genotype-The totality of an individual’s genes • Phenotype-Actual Characteristics • This is what is seen or observed and can include a wide range of things

  4. Studies of identical twins illustrate how different factors like smoking, sun exposure, depression and weight gain can influence aging. Age 52. The twin on the left smokes and has a history of more sun exposure, resulting in an older appearance than her twin of the same age. Photo: Dr. Bahman Guyuron

  5. Genetic BasicsExpression of Traits • Dominant Genes-Expressed characteristics • Recessive Genes-Not expressed, although it is a part of the genotype (genetic background) • Allele-Alternate form of a gene • Dominant-Recessive Inheritance

  6. Table 2.1 Traits With Single-Gene Dominant–Recessive Inheritance

  7. Genetic BasicsExpression of Traits • Incomplete Dominance • Phenotype influenced primarily but not exclusively by the dominant gene • Polygenic Inheritance • Interaction of multiple genes

  8. Genetic BasicsThe Sex Chromosomes • The 23rd chromosomes pair determine male or female • Males more vulnerable to X-linked recessive disorders

  9. Genetic BasicsGenes and Environment • Behavior Genetics • Estimating influence of genes and environment on development • Utilize twins to understand importance of genetics and tease out environment effects

  10. Genetic BasicsGenes and Environment • Heritability • An estimate of the extent to which genes are responsible for differences among persons within a specific population • Concordance Rates • Percentage that indicates degree of similarity in phenotype among pairs of family members

  11. The Human ExperienceConception and Prenatal Development

  12. Sperm and Egg FormationCell Division

  13. The Beginning of LifeConception • For conception to occur there must be a released ovum and a sperm. • Ovulation releases the ovum, and if sperm available, fertilization can occur.

  14. The Germinal PeriodFirst 2 Weeks of Life • During the travel from the fallopian tube to the uterus cell division is taking place • Blastocyst • Trophoblast • Embryonic disk

  15. The Embryonic PeriodWeek 3-Week 8 • Key Developments • Embryonic Layers • Ectoderm • Mesoderm • Endoderm

  16. The Embryonic PeriodWeek 3-Week 8 • Key organs and structures are forming including • Heartbeat • Eyes, nose and mouth • Bone development • Arm and leg buds • Digestive system

  17. The Fetal PeriodWeek 9-Birth • The longest period of prenatal development • Heartbeat can be heard • Movement can be felt • Responds to sounds • Main impediment to viability is lung development

  18. The Fetal PeriodWeek 9-Birth

  19. Prenatal CareTraditional Cultures and Beliefs • Prenatal beliefs are impacted by generational wisdom of the time • These beliefs can include • Avoiding wine • Specific types of meat • Certain types of hot, cold food • Witches • Strong foods

  20. Prenatal CareScience Driven Prenatal Care • Some current science-driven prenatal methods are derived from traditional cultures which includes massages • Current care can vary by ethnicity and SES • Developing world less likely to receive prenatal care • Current focus on diet, exercise, and teratogens

  21. Map 2.1 Ethnic Variations in Prenatal Care within the United States How does prenatal care differ for White women compared with other ethnic groups? What economic factors might account for these variations?

  22. Prenatal CareDiet • Two key vitamins are iodine and iron • Iodine deficiency tends to be a bigger issue in developing countries • Iron is necessary for a healthy pregnancy

  23. Prenatal CareExercise • Continued physical activity is encouraged during pregnancy • Aerobic exercise encourages good cardiovascular health and positively benefits the fetus • A Non-aerobic exercise called Kegel exercises are also encouraged

  24. Prenatal CareTeratogens • Teratogens are environmental and bodily conditions that could be harmful • They can include tobacco, alcohol, prescription medications and other drugs • The physical environment could also be a teratogen due to malnutrition or exposure to hazardous chemicals

  25. Safety sign. Source: http://www.compliancesigns.com

  26. Pregnancy Problems

  27. Chromosomal Disorders • Chromosomal disorders can occur because of an issue during meiosis • This may cause too many or too few chromosomes in the cells of the zygote • Two types of chromosomal disorders are: • Sex chromosome disorders • Disorder on the 21st chromosome (Down Syndrome)

  28. Sex Chromosome Disorders • Sex chromosomal disorder can result from extra X, an extra Y, or only an X and no second chromosome • Common consequences of sex chromosome disorders include: • Cognitive Deficit • Abnormality in reproductive system at puberty

  29. Down SyndromeTrisomy 21 • Identifiable by physical characteristics • Cognitive Deficits • Speech problems • Mental retardation • Social development varies • Lower life expectancy

  30. Parental Age and Chromosomal Disorder • Chromosomal disorders tend to NOT be passed from parent to child • Relationship between maternal age and chromosomal disorders • There may be a relationship between a father’s age and chromosomal disorders but it isn’t as clear

  31. Figure 2.7 Chromosomal Disorders and Maternal Age Why does the risk rise so steeply after age 40? Source: Reproductive Medicine Associates of New Jersey, 2002

  32. Teratogens • Major teratogens exist in both developed and developing countries • Malnutrition • Infectious Disease • Alcohol • Tobacco

  33. TeratogensTiming of Teratogens • Teratogens can impact the developing fetus and embryo at any time • There does appear to be a critical period of prenatal development centered in the embryonic period

  34. TeratogensTiming of Teratogens

  35. TeratogensMalnutrition • Rural nature of half the world’s population impacts nutrition • Children’s health could vary based on country or area of conception

  36. TeratogensMalnutrition • Developed countries have food available but may have malnutrition • May be deficient in specific vitamins or improper diet may lead to obesity • Maternal obesity is linked to baby complications • Prenatal nutrition can also cause prenatal problems

  37. TeratogensInfectious Diseases • Rubella (German Measles) • Exposure during embryonic stage can lead to heart abnormalities and mental retardation • Exposure during the fetal stage can lead to hearing problems and low birth weight • Vaccination can help but Rubella remains widespread in less developed countries

  38. TeratogensInfectious Diseases • AIDS (Acquired Immune Deficiency Syndrome) • Three strategies can help prevent transmission • Effective medicines • Cesarean sections for AIDS-infected moms • Infant formula in place of breast feeding

  39. TeratogensDrugs-Alcohol • Widespread damage in developed countries • Fetal Alcohol Spectrum Disorder • Increased effects as child develops

  40. TeratogensDrugs-Tobacco • Maternal smoking increases risk of miscarriages, premature birth and low birth weight • Infant effects include difficulty breathing and impaired heart functioning

  41. TeratogensDrugs-Tobacco • Childhood effects include poorer language skills, attention and memory problems and behavior problems • Second hand smoke by fathers is also detrimental

  42. TeratogensDrugs • Malnutrition and diseases are common in developing countries • Alcohol and tobacco are common in developed countries • Prescription drugs can be damaging • Other teratogens include non-prescription drugs, severe stress, pollution and radiation

  43. Prenatal Diagnosis • Ultrasounds-Uses high frequency sound waves • Amniocentesis-Utilizes amniotic fluid • ChorionicVillusSampling-Utilizes cells from forming umbilical cord

  44. InfertilityCauses • For men three main causes • Too few sperm • Quality of sperm • Low motility • For women many causes • One is ovulation

  45. Figure 2.9 Fertility and Maternal Age Why does fertility decline after the mid-twenties? Source: Reproductive Medicine Associates of New Jersey, 2002

  46. InfertilityTreatments • Historical treatments of infertility included: • Giving more attention to wife to achieve mutual orgasm • Surgery on a woman’s anatomy • Bloodletting • Current treatments are more advanced

  47. InfertilityTreatments • Many treatments utilize Assisted Reproductive Technologies (ART) • Artificial Insemination • Injects sperm into woman’s uterus • Fertility Drugs • Mimic hormones involved in ovulation • In-vitro fertilization • Ova removed and fertilized outside the womb then placed into uterus

  48. Map 2.2 The “Infertility Belt” In certain countries in Central Africa, infertility rates are as high as 30%. The reasons for this are unclear although malnutrition and high rates of STIs are probable factors.

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