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Day 3 Notes: Genetics

June 20, 2013 by  

Genetics: building blocks of life

Genetics

Stuff goes here….random words about hallucinations and delusions, schizophrenia is chronic, severe and disabling condition. There is no clear cause and no known cure.

Let’s try to make an outline:

  • Genetics
  • Gregor Mendel (1822-1884)
    • 1st experimental study genetics
    • Took long walks, found unusual ornamental plant
    • Planted it next to typical variety
    • Grew progeny side by side
    • Found
      • Offspring show essential traits of parents
      • Not influenced by environment
      • Each transmits only half its hereditary factors to its offspring
      • Different offspring of same parents receive diff set of hereditary factors
      • Traits inherited in certain ratios
      • Genes dominant or recessive
      • Factors are inherited intact
  • Humans
    • 46 chromosomes
    • 23 from each; paired
    • 25,000 genes (all together)
    • Two copies, 1 from each
    • Matching is by chance
      • Shuffling
      • Unique combination
    • Genes affect structures
    • No single gene causes any behavior
  • Dominant = single copy from either parent carries trait
    • Heterozygous = coded differently
  • Recessive
    • Copy from each parent required
    • Can unknowingly carry disease
    • Can be hidden for generations
    • Affected parent (Dad or Mum)
    • All children have equal chance of inheritance
  • Dominant-Recessive
    • Dominant Wins ¾ Times
    • Dominant Dominant
    • Dominant Recessive
    • Recessive Dominant
    • Recessive Recessive
  • Mendel’s peas
    • smooth or wrinkled
    • green or yellow
    • short or tall
  • Incomplete Recessive
    • In some flowers
    • Red and white produce pink
  • In humans
    • Most cases that look incomplete
    • Multiple mutations
      • Tay-Sachs disease
        • 2 different recessive mutations
      • Sickle Cell Anemia
        • Carriers show no symptoms
        • Unless climb mountains (low oxygen)
  • Single Traits
    • 1. Autosomal Traits
      • Not X or Y
      • Autosomal = equal in each sex
        • Single gene on an autosome (non-sex chromosome)
      • Dominant Trait Examples:
        • Huntington’s disease
        • Neurological disease
        • Many copies of gene segment
        • Recessive Trait Examples:
          • Albinism
          • Cystic Fibrosis
      • Affected parent (Dad or Mum)
        • Children have 50% of inheriting one mutated allele
        • Either get yours or spouse’s
        • Makes you a carrier
      • Carrier
        • One mutated allele
        • One normal allele
        • Allele = gene option (green or yellow)
        • Put two carriers together
          • 25% chance will transmit mutated gene
          • 1 will be unaffected
          • 2 will be carriers
          • 1 will be affected
          • Get 2 bad copies
    • 2. Sex-Linked Traits
      • Sex-linked = appear in only one sex
      • X-Chromosome Linked
        • Females
        • Inherit X from mother
        • Inherit X from father’s mother
        • Healthy copy beats unhealthy
        • Problems in women only when both copies flawed
          • Rare
        • Have 1 bad copy = carrier
        • Have 2 bad copies = show trait
      • Y-Chromosome
        • Most genes come in pairs
        • Except males
        • One Y chromosome
        • One X chromosome
        • Get X chrom. from mother
        • Only one copy
        • No backup
      • Y-Linked Traits
        • Only in men
        • Traits passed from father to son
        • Few genes on Y chromosome
        • Coffin-Lowry Syndrome
          • Mutation in ribosomal protein gene
          • Mental retardation
          • Short stature
          • Craniofacial
          • Skeleton
        • Male Pattern Baldness
          • Begins in front, move backward
          • M shape, then U-shaped
          • Current best gues
          • Susceptibility Y-linked; can pass on to son
          • Hair structure X-linked
    • 3. Sex-limited Traits
      • Autosomal traits that are expressed differently in males & females
      • Sex-limited = appear in both
      • Male & female elephant seals
  • Single Gene Disorders
    • 4000+
    • Cystic Fibrosis
    • Hemophilia
    • Sickle cell
    • PKU (Phenylketonuria)
      • Autosomal Recession
      • 100% genetic
      • Nonfunctional hepatic enzyme
      • Can’t process amino acid (phenylalanine)
      • Can lead to
        • mental retardation & seizures
        • death at young age
      • Diet without substances that need enzyme
        • 100% environment
      • Two factors
      • Gene
      • Diet
  • Polygencic Disorders
    • Complex & multifactorial
    • Multiple genes in combination
      • 10 genes involved in eye color
    • Cluster in families
      • No clear pattern
      • Run in families
    • Also lifestyle and environment
    • Examples
      • Multiple Sclerosis
      • Heart disease & hypertension
      • Asthma
      • Mood disorders
      • Cleft palate
      • Obesity
      • Cancer

 

 

 

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