G & D Ch. 2

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Biological Beginnings

Biological Beginnings

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  • 1. CHAPTER 2 Biological Beginnings
  • 2. Mechanisms of Heredity
    • 23 Chromosomes in Each Egg and Sperm
    • 22 Pairs Plus Sex Chromosomes
    • Polygenetic Inheritance
    • Behavioral Genetics
    • Twin and Adopted Children Studies
  • 3. Important Terms
    • Chromosomes
    • Rod-shaped portions of DNA organized into 23 pairs
    • Gametes
    • Sperm & ova
    • Zygote
    • Fertilized egg
    • Genotype
    • Underlying combination of genetic material in an organism
    • Phenotype
    • Observable trait
    • Polygenic Inheritance
    • A combination of genes produces a trait
    • X-Linked Genes
    • Located on the X chromosome
    • Alleles
    • Variations of genes
    • Homozygous genes
    • Alleles in a pair of chromosomes that are the same
    • Heterozygous genes
    • Alleles that are different
    • Dominant genes
    • Chemical instructions are followed
    • Recessive genes
    • Chemical instructions are ignored
    • Mutation
    • A chromosomal abnormality
  • 4. Behavioral Genetics
    • Branch of genetics that deals with the inheritance of behavioral & psychological traits
    • Polygenetic inheritance:
    • Phenotypes reflecting the combined activity of many separate genes
  • 5. Twin and Adopted Children Studies
    • Monozygotic Twins:
    • Identical twins
    • Dizygotic Twins:
    • Fraternal twins
  • 6. Genetic Disorders
    • PKU
    • Inherited disorder where an individual lacks an enzyme that converts phenylalanine;
    • Phenylalanine accumulates & produces toxins that harm the nervous system resulting in mental retardation
    • Huntington’s Disease
    • Inherited disorder caused by dominant gene that produces a progressive dementia;
    • On chromosome 4
  • 7. Abnormal Chromosomes
    • Abnormal Complement of 46 Chromosomes
    • May have extra, missing, or damaged chromosomes
    • Down syndrome:
    • Trisomy 21
    • For woman over 40, risk is 1 in 50
  • 8. Sickle-Cell
    • A Blood Disorder that gets its name from the shape of the red blood cells that have it
    • Renders one immune to malaria but tends to die young.
  • 9. Fragile X Syndrome
    • A disorder produced by injury to a gene on the X chromosome, producing mild to moderate mental retardation
  • 10. Tay-Sacks Disease
    • A genetic disorder that produces blindness & muscle degeneration prior to death
  • 11. Klinefelter’s Syndrome
    • A Disorder due to an extra X chromosome
    • It produces underdeveloped genitals, extreme height, & enlarged breasts
  • 12. Genes & The Environment
    • From Genes to Behavior
    • Genes influence Behavior Indirectly
    • Genetic predispositions
    • Consequences of Genetic Instructions Depend on the Environment
    • Reaction Range
    • A Genotype is Manifested in Reaction to the Environment where Development Takes Place
  • 13. Genes & The Environment
    • Relations Between Nature & Nurture
    • Passive Gene-environment Relation:
    • Genotypes & early environment passed from parents to children
    • Evocative Gene-environment Relation:
    • Differing responses from the environment evoked by different genotypes
    • Active Gene-environment Relation:
    • Seeking environments related to genetic makeup
    • The Nature of Nurture
    • Nonshared Environmental Influences:
    • Family dynamics that make children different
  • 14. Germinal Period (1 – 2 Weeks)
    • Fertilization
    • Begins period of Zygote
    • Zygote is term for fertilized egg
    • Of the 200 – 500 million sperm only a few hundred will make the journey up the fallopian tubes
    • Implantation
    • When zygote burrows into uterine wall and makes connections w/blood supply
    • Germ Disc
    • Small cluster of cells near center of zygote that eventually develop into a baby
    • Placenta
    • Structure through which nutrients & wastes are exchanged between mother & baby
  • 15. Embryonic Period (3 – 8 Weeks)
    • Embryo
    • Once the zygote is imbedded in uterine wall it is called embryo
    • Dermal layers:
    • Ectoderm-
    • Outer layer that develops into hair, outer layer of skin & nervous system
    • Mesoderm-
    • Middle layer that develops into muscles, bones, & circulatory system
    • Endoderm-
    • Inner layer that develops into digestive system & lungs
  • 16. Fetal Period (9 – 38 Weeks)
    • Final & Longest Phase of Prenatal Development
    • Ends in birth
    • Baby grows & bodily systems begin working
    • Age of Viability
    • 22 – 28 Weeks
    • Most systems function well enough that fetus has chance of surviving
  • 17. Influences on Prenatal Development
    • General Risk Factors
    • Nutrition
    • Most women need to increase calorie intake by 10% to 20%
    • Needs adequate vitamins & minerals
    • Inadequate nourishment during the last months of pregnancy can affect the nervous system & immune system of infant
    • Stress
    • Increased stress is harmful
    • Mother’s stress can reduce the flow of oxygen to the fetus which increases heart rate & activity level
    • can weaken mother’s immune system making her more susceptible to illness damaging fetal development
    • Stress can provoke smoking & drinking ending in FAS &/or premature or low-birthweight babies
    • Mother’s Age
    • Teenage motherhood
    • Incomplete education, poverty, & marital difficulties affecting child’s later development
    • Older mothers
    • Less fertility, higher chance of miscarriage & stillbirth, increased chance of Down syndrome
  • 18. Teratogens
    • Agent that causes abnormal prenatal development
    • Drugs
    • Cigarette Smoking constricts blood vessels reducing oxygen & nutrients to the fetus
    • Increased chance of miscarriage & low birthweight
    • Child will show signs of impaired attention, language, & cognitive skills, as well as behavioral problems
    • Diseases
    • AIDS, Genital Herpes, Rubella, Syphilis
    • Environmental Hazards
    • Lead, Mercury, PCBs, X-rays & VDTs (Latest data indicates no risk with VDTs)
    • Influence on Prenatal Development
    • Depends on the genotype of the organism
    • Impact changes over course of prenatal development
    • Each teratogen affects a specific aspect of prenatal development
    • Depends on the dosage
    • Damage is not always present at birth but can appear later
  • 19. Stages of Labor
    • Stage 1
    • May last from 12 – 14 hours for 1st birth
    • Uterus begins contracting weak & irregularly
    • When stronger & more rhythmic, enlarges cervix
    • Stage 2
    • Baby passes through cervix entering vagina
    • Mother’s pushing helps baby along
    • when top of baby’s head appears (crowning) delivery is in about 1 hour
    • Stage 3
    • Lasts only a few minutes
    • Mother’s pushing expels the placenta
  • 20. Approaches to Childbirth
    • Prepared Approaches
    • Natural Childbirth
    • LaMaze
    • LeBoyer
    • Cesarian
  • 21. Complications
    • Disruptions
    • Irregular Position
    • Breech or Shoulder-first Position
    • Enlarged Head
    • Anoxia: Umbilical cord shuts off oxygen
    • Preterm
    • Low Birthweight
  • 22. Infant Mortality
    • Number of Infants out of 1000 births who die before their 1st birthday
    • U.S. has very HIGH infant mortality
    • Most other countries provide extensive care for little or no cost