Earliest Development

  • Gametes­ sex cells that form new cell at conception o Sperm, ovum
  • Zygote­ new cell formed by fertilization o Genes­ basic units of genetic information o DNA molecules­ make up genes
    • Chromosomes­ rod­shaped portions of DNA
  • 46 arranged into 23 pairs
  • Males are heterogametic= XY
  • Females are homogametic= XX
  • Father determines the sex of the zygote

Multiple Births

  • Rare in humans­ less than 3% of births are multiples
  • Triplets, quadruplets, ect.­ more common with fertility treatments, advanced age of mother
  • Monozygotic­ aka identical, maternal twins­ 30% of twins­ 1 zygote Dizygotic­ aka fraternal twins­ 70% of twins­ 2 zygotes
  • Identical not really identical­ different fingerprints, ect.
  • Further along in pregnancy before zygote splits, more similarity
  • Dizygotic= no more similar than any other siblings From Genotype to Phenotype
  • Genotype­ inherited genes
  • Phenotypes­ expression of genes Influences on Gene Expression
  • Genetic interactions­ genes can contain conflicting info; may split the difference o Dominant­recessive patter­ ex: eye color
    • Polygenetic inheritance­ combination of several genes responsible for a trait
  • Gene­environment interactions­ environment can affect how genes are expressed
    • Ex: height
    • Reaction range­ range of possibilities determined by genes
  • Inherited and Genetic Abnormalities o Failure of chromosomes to divide evenly; spontaneous mutations o Up to 1/2 of zygotes have chromosomal abnormalities; most miscarried o 1 in 200 live births
  • Down Syndrome: aka trisomy 21. 3 chromosomes at 21 chromosome pair

   Characteristics facial features; heart defects; hearing problems; developmental delays (highly variable)

  • Kleinfelter’s Syndrome: 1/400 males; extra X chromosome

               Underdeveloped genitals; enlarged breasts; extreme height; learning disabilities

  • Fragile X Syndrome: males and females; malformation on X chromosome

             Some, no signs; others, mild­ moderate developmental delays

  • Turner Syndrome: only females; only 1 X chromosome

   Short; webbed neck; little breast development; learning disabilities; difficulty recognizing emotional facial cues

  • Sickle cell Anemia: more common in AA populations; disorder of red blood cells
    • Normal red blood cells= doughnut without the hole
    • Sickle cells= crescent shaped; sticky and stiff
    • Block blood flow to limbs and organs
  • Tay­Sachs disease: born without enzyme that clears out unwanted material in brain  Affects sight, hearing, movement, mental dev.
    • More common in certain groups­ Ashkenazi, Jews, ect.
    • No treatment, always fatal

Genetic Counseling

  • Evaluating family history, medical records
  • Genetic testing
  • Evaluating results
  • Helping parents understand results; decide what to do next
  • *Review different types of prenatal tests in text*

Behavioral Genetics

  • Effects of heredity on behavior
  • Some char’s determined entirely by genes; others by interactions between genes and environment
  • Relative weight of each
  • Heritability applies to populations; NOT individuals
  • Ex: height
  • Methods of Investigation:
  • Family Studies­ easy to find
    • Problem: share environments as well as genetics
    • Good place to start
    • Twin studies­ comparing similarity for a trait in MZ vs DZ twin sets
    • Both types share the environment (though MZ may share more than DZ); difference lies

in amount of shared DNA

  • If MZ twins are more similar than DZ= genetic component
    • In both types, equally similar= shared environmental imput
  • Adoption studies­ compare child to adoptive and biological parents for similarity on a characteristic.
  • More similar to bio= genetic influence
  • More similar to adoptive= environmental influence
    • Cons­ difficult to find kids; privacy issues; difference in parents
  • Adoptive­ older, richer, healthier

 

Prenatal Growth and Change

The Stages of Prenatal Development

  • 1.The Germinal Stage­ fer­2 weeks
    • Fertilization occurs in fallopian tubes; zygote must travel to uterus to implant
    • Cells divide exponentially­ a 8 cell stage, cell differentiation starts
    • Outer cells­ placenta­ connection between mother and fetus; nutrition/ oxygen via umbilical cord
    • Inner cells­ embryo
  • 1.Embryonic­ 2­8 weeks. Embryo­ 3layers
    • Ectoderm­ skin and nervous system
    • Endoderm­ dif]gestive and respitory system
    • Mesoderm­ muscle and skeletal systems
    • 22 days afetr fertilization­ neural tube
  • 1.Fetal stage­ 8 weeks­ birth. Fetus
    • Organ development, overall growth
    • Becoming more obvious
    • By the end of the month, all parts of the body are present. 3 oz
    • 7 months­ birth­ putting on weight, getting ready for life outside womb Threats to Development
    • Teratogens­ harmful environmental effects that can affect fetus o Timing is important; in general, earlier in pregnancy, more harmful effects will be o Different organs/systems have different critical periods
  • 1.Mother’s Diet­ not usually a problem in WEIRD cultures o Malnutrition harms mother and fetus
  • 2.Mother’s Age­ usually young/ old­ difficult pregnancy, premature birth, low birth weight
  • 3.Maternal Drug Use­ legal and illegal o Thalidomide­ morning sickness
  • Phocomelia­ stunted arms, legs
    • Smoking­ low oxygen levels
      • Low birth weight­ compromised immune system; poor respiration, mental retardation,

miscarriage, asthma, SIDS

  • Alcohol­ fetal alcohol syndrome­ heart defects, facial/body abnormalities, mental retardation
    • Most common non­genetic form of mental retardation
  • Cocaine­ low birth weight, low oxygen levels, neurological impairment
    • Difficult to separate bad prenatal care from effects of drug
    • .Maternal Disease­ herpes, rubella, AIDS o AIDS­ with antivirals, less than 5% born with HIV o Herpes­ Cesarean section can prevent transmission