g & d ch. 2
DESCRIPTION
Biological BeginningsTRANSCRIPT
CHAPTER 2CHAPTER 2
Biological Biological BeginningsBeginnings
Mechanisms of Heredity
23 Chromosomes in Each Egg and Sperm
22 Pairs Plus Sex
Chromosomes
Polygenetic Inheritance
Behavioral Genetics
Twin and Adopted Children
Studies
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
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
Twin and Adopted Children Twin and Adopted Children StudiesStudies
Monozygotic Monozygotic Twins:Twins:
Identical Identical twinstwins
Dizygotic Dizygotic Twins:Twins:
Fraternal Fraternal twinstwins
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
Approaches to ChildbirthApproaches to Childbirth
Prepared Prepared ApproachesApproachesNatural ChildbirthNatural Childbirth
LaMazeLaMaze
LeBoyerLeBoyer
CesarianCesarian
ComplicationsComplications
Disruptions Irregular Position Breech or Shoulder-first Position
Enlarged Head
Anoxia: Umbilical cord shuts off oxygen
Preterm
Low Birthweight
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