Hereditary Influences on Development

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Hereditary Influences on Development

• Chapter 3

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The Genetic Code

• Chromosomes
• Rodlike
• Store and transmit genetic information
• Matching pairs
• 46 chromosomes, 23 pairs
• Comprised of deoxyribonucleic acid, DNA

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Gametes/Sex Cells

• Sperm, ovum
• Contain only 23 chromosomes
• Formed through meiosis
• Regular body cells ? mitosis
• Sex cells ? meiosis
• Crossing over

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Multiple Offspring

• Identical/monozygotic twins
• Fraternal/dizygotic twins

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Patterns of Genetic Influence

• Phenotype
• Genotype
• Can have same phenotype but different
  genotypeswhy?

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How Are Genes Expressed?

• Simple dominant-recessive inheritance
• Each different form of a gene is called an allele
• Alleles alike homozygousAlleles different
  heterozygous

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How Are Genes Expressed?

• Dominant-recessive

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Examples of Dominant-Recessive Genes Dominant
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
• widows peak normal hairline
• sex-linked characteristic

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Examples of Dominant-Recessive Genes Dominant
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

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Examples of Dominant-Recessive Genes Dominant
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

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How Are Genes Expressed?

• If heterozygous, can pass on a recessive allele
  to children
• Carriers
• Phenylketonuria (PKU)

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How Are Genes Expressed?

• Sex-linked inheritance
• Codominance
• Polygenic inheritance

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Hereditary Disorders

• Chromosomal abnormalities

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Hereditary Disorders

• Autosomal abnormalities
• Most frequent is Down syndrome (trisomy 21)
• Mental retardation
• Distinctive physical features
• Mutations

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Detecting Hereditary Disorders

• Amniocentesis
• Chorionic villus sampling
• Ultrasound
• Know the procedures, advantages, and
  disadvantages of each

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Genetic-Environmental Interactions

• Reaction range

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Range of Reaction
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Canalization

• Heredity restricts development of some
  characteristics
• Examples babbling, motor development

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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

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Behavioral Genetics

• Twin studies
• Identical/fraternal reared together
• Adoption studies
• Identical twins reared apart
• Calculate concordance rates
• Heritability coefficient

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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)

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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

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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

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Molecular Genetics

• To discover the precise locations of genes that
  determine an individuals susceptibility to
  various diseases and other aspects of health and
  well-being
• Genome complete set of instructions for making
  an organism
• Human Genome Project