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Hereditary Influences on Development. Chapter 3. The Genetic Code. Chromosomes Rodlike Store and transmit genetic information Matching pairs 46 chromosomes, 23 pairs… Comprised of deoxyribonucleic acid, DNA. Gametes/Sex Cells. Sperm, ovum Contain only 23 chromosomes

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the genetic code
The Genetic Code
  • Chromosomes
    • Rodlike
    • Store and transmit genetic information
    • Matching pairs
    • 46 chromosomes, 23 pairs…
  • Comprised of deoxyribonucleic acid, DNA
gametes sex cells
Gametes/Sex Cells
  • Sperm, ovum
  • Contain only 23 chromosomes
  • Formed through meiosis
  • “Regular” body cells  mitosis
  • Sex cells  meiosis
  • Crossing over
multiple offspring
Multiple Offspring
  • Identical/monozygotic twins
  • Fraternal/dizygotic twins
patterns of genetic influence
Patterns of Genetic Influence
  • Phenotype
  • Genotype
  • Can have same phenotype but different genotypes…why?
how are genes expressed
How Are Genes Expressed?
  • Simple dominant-recessive inheritance
    • Each different form of a gene is called an allele
    • Alleles alike = homozygousAlleles different = heterozygous
how are genes expressed12
How Are Genes Expressed?
  • Dominant-recessive
examples of dominant recessive genes dominant traits recessive traits
Examples of Dominant-Recessive GenesDominant Traits Recessive Traits

Eye color brown eyes grey, green, hazel, blue

Vision farsightedness normal vision

normal vision nearsightedness

normal vision night blindness

normal vision color blindness*

Hair dark hair blonde, light, red hair

non-red hair red hair

curly hair straight hair

full head of hair baldness*

widow’s peak normal hairline

*sex-linked characteristic

examples of dominant recessive genes dominant traits recessive traits15
Examples of Dominant-Recessive GenesDominant Traits Recessive Traits

Facial features dimples no dimples

unattached earlobes attached earlobes

freckles no freckles

broad lips thin lips

Appendages extra digits normal number

fused digits normal digits

short digits normal digits

fingers lack 1 joint normal joints

limb dwarfing normal proportion

clubbed thumb normal thumb

double-jointedness normal joints

examples of dominant recessive genes dominant traits recessive traits16
Examples of Dominant-Recessive GenesDominant Traits Recessive Traits

Other immunity to poison ivy susceptibility to poison ivy

normal pigmented skin albinism

normal blood clotting hemophilia*

normal hearing congenital deafness

normal hearing and speaking deaf mutism

normal – no PKU phenylketonuria (PKU)

*sex-linked characteristic

how are genes expressed17
How Are Genes Expressed?
  • If heterozygous, can pass on a recessive allele to children
    • Carriers
  • Phenylketonuria (PKU)
how are genes expressed18
How Are Genes Expressed?
  • Sex-linked inheritance
  • Codominance
  • Polygenic inheritance
hereditary disorders
Hereditary Disorders
  • Chromosomal abnormalities
hereditary disorders21
Hereditary Disorders
  • Autosomal abnormalities
    • Most frequent is Down syndrome (trisomy 21)
    • Mental retardation
    • Distinctive physical features
  • Mutations
detecting hereditary disorders
Detecting Hereditary Disorders
  • Amniocentesis
  • Chorionic villus sampling
  • Ultrasound
  • Know the procedures, advantages, and disadvantages of each…
canalization
Canalization
  • Heredity restricts development of some characteristics
  • Examples = babbling, motor development
behavioral genetics
Behavioral Genetics
  • The scientific study of how genotype interacts with the environment to determine behavioral attributes such as intelligence, personality, and mental health
  • Methods of studying hereditary influences
    • Selective breeding
    • Family studies
      • Twin studies
      • Adoption studies
behavioral genetics27
Behavioral Genetics
  • Twin studies
    • Identical/fraternal reared together
    • Adoption studies
    • Identical twins reared apart
  • Calculate concordance rates
  • Heritability coefficient
behavioral genetics28
Behavioral Genetics
  • Heritability coefficient (H) = (r identical – r fraternal) X 2
  • Environmental influences
    • Nonshared environmental influences (NSE)
      • 1 – r identical twins reared together
    • Shared environment influences
      • 1 - (H + NSE)
behavioral genetics29
Behavioral Genetics
  • Anxiety scale score
    • Monozygotic twins: r = .78
    • Dizygotic twins: r = .51
    • Heritability:
      • 2(.78-.51)
      • 2(.27)
      • .54
    • Nonshared:
      • 1 - .78 = .22
    • Shared:
      • 1 – (.54 + .22)
      • 1 - .76 = .24
behavioral genetics30
Behavioral Genetics
  • Favorite color
    • Monozygotic twins: r = .26
    • Dizygotic twins: r = .23
    • Heritability:
      • 2(.26-.23)
      • 2(.03)
      • .06
    • Nonshared:
      • 1 - .26 = .74
    • Shared:
      • 1 – (.06 + .74)
      • 1 - .80 = .20
molecular genetics
Molecular Genetics
  • To discover the precise locations of genes that determine an individual’s susceptibility to various diseases and other aspects of health and well-being
  • Genome = complete set of instructions for making an organism
  • Human Genome Project