g & d ch. 2

22
CHAPTER 2 CHAPTER 2 Biological Biological Beginnings Beginnings

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Biological Beginnings

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Page 1: G & D Ch. 2

CHAPTER 2CHAPTER 2

Biological Biological BeginningsBeginnings

Page 2: G & D Ch. 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

Page 3: G & D Ch. 2

Important TermsChromosomesRod-shaped portions of DNA organized into 23 pairs

GametesSperm & ova

ZygoteFertilized egg

GenotypeUnderlying combination of genetic material in an organism

PhenotypeObservable trait

Polygenic InheritanceA combination of genes produces a trait

X-Linked GenesLocated on the X chromosomeAllelesVariations of genesHomozygous genesAlleles in a pair of chromosomes that are the sameHeterozygous genesAlleles that are differentDominant genesChemical instructions are followedRecessive genesChemical instructions are ignoredMutationA chromosomal abnormality

Page 4: G & D Ch. 2

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

Page 5: G & D Ch. 2

Twin and Adopted Children Twin and Adopted Children StudiesStudies

Monozygotic Monozygotic Twins:Twins:

Identical Identical twinstwins

Dizygotic Dizygotic Twins:Twins:

Fraternal Fraternal twinstwins

Page 6: G & D Ch. 2

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

Page 7: G & D Ch. 2

Abnormal Abnormal ChromosomesChromosomes

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

Page 8: G & D Ch. 2

Sickle-CellSickle-CellA Blood Disorder that gets its name from the shape of the red blood cells that have itRenders one immune to malaria but tends to die young.

Page 9: G & D Ch. 2

Fragile X Fragile X SyndromeSyndrome

A disorder produced A disorder produced by injury to a gene on by injury to a gene on the X chromosome, the X chromosome, producing mild to producing mild to moderate mental moderate mental retardationretardation

Page 10: G & D Ch. 2

Tay-Sacks DiseaseTay-Sacks DiseaseA genetic A genetic disorder that disorder that produces produces blindness & blindness & muscle muscle degeneration degeneration prior to deathprior to death

Page 11: G & D Ch. 2

Klinefelter’s SyndromeKlinefelter’s SyndromeA Disorder A Disorder due to an due to an extra X extra X chromosomechromosomeIt produces underdeveloped It produces underdeveloped genitals, extreme height, & genitals, extreme height, & enlarged breastsenlarged breasts

Page 12: G & D Ch. 2

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

Page 13: G & D Ch. 2

Genes & The EnvironmentRelations 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 NurtureNonshared Environmental Influences: Family dynamics that make children different

Page 14: G & D Ch. 2

Germinal Period (1 – 2 Germinal Period (1 – 2 Weeks)Weeks)

FertilizationBegins 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

ImplantationWhen 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

Page 15: G & D Ch. 2

Embryonic Period (3 – 8 Embryonic Period (3 – 8 Weeks)Weeks)

EmbryoEmbryo Once the zygote is imbedded in Once the zygote is imbedded in uterine wall it is called uterine wall it is called embryoembryo 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

Page 16: G & D Ch. 2

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

Page 17: G & D Ch. 2

Influences on Prenatal Development

General Risk Factors NutritionMost 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 StressIncreased 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 AgeTeenage motherhood Incomplete education, poverty, & marital difficulties affecting child’s later developmentOlder mothers Less fertility, higher chance of miscarriage & stillbirth, increased chance of Down syndrome

Page 18: G & D Ch. 2

TeratogensTeratogens Agent that causes abnormal Agent that causes abnormal prenatal developmentprenatal development DrugsDrugsCigarette Smoking constricts Cigarette Smoking constricts blood vessels reducing blood vessels reducing oxygen & nutrients to the oxygen & nutrients to the fetusfetusIncreased chance of Increased chance of miscarriage & low birthweightmiscarriage & low birthweight Child will show signs of Child will show signs of impaired attention, language, impaired attention, language, & cognitive skills, as well as & cognitive skills, as well as behavioral problemsbehavioral problems

DiseasesDiseasesAIDS, Genital Herpes, Rubella, AIDS, Genital Herpes, Rubella, SyphilisSyphilis

Environmental HazardsEnvironmental Hazards Lead, Mercury, PCBs, X-rays & Lead, Mercury, PCBs, X-rays & VDTsVDTs (Latest data indicates no (Latest data indicates no risk with VDTs)risk with VDTs)

Influence on Prenatal Influence on Prenatal DevelopmentDevelopment Depends on the genotype Depends on the genotype of the organismof the organismImpact changes over Impact changes over course of prenatal course of prenatal developmentdevelopment Each teratogen affects a Each teratogen affects a specific aspect of prenatal specific aspect of prenatal developmentdevelopment Depends on the dosageDepends on the dosage Damage is not always Damage is not always present at birth but can present at birth but can appear laterappear later

Page 19: G & D Ch. 2

Stages of LaborStages of Labor Stage 1May last from 12 – 14 hours for 1st birthUterus begins contracting weak & irregularly When stronger & more rhythmic, enlarges cervix

Stage 2Baby passes through cervix entering vagina Mother’s pushing helps baby alongwhen top of baby’s head appears (crowning) delivery is in about 1 hour

Stage 3 Lasts only a few minutesMother’s pushing expels the placenta

Page 20: G & D Ch. 2

Approaches to ChildbirthApproaches to Childbirth

Prepared Prepared ApproachesApproachesNatural ChildbirthNatural Childbirth

LaMazeLaMaze

LeBoyerLeBoyer

CesarianCesarian

Page 21: G & D Ch. 2

ComplicationsComplications

Disruptions Irregular Position Breech or Shoulder-first Position

Enlarged Head

Anoxia: Umbilical cord shuts off oxygen

Preterm

Low Birthweight

Page 22: G & D Ch. 2

Infant MortalityInfant Mortality

Number of Infants Number of Infants out of 1000 births out of 1000 births who die before their who die before their 1st birthday1st birthdayU.S. has very HIGH U.S. has very HIGH infant mortalityinfant mortality

Most other countries provide Most other countries provide extensive care for little or no extensive care for little or no

costcost