Human%20Genetics

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Human Genetics

• BSC 2010L

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Note that we have 22 pairs of autosomal
chromosomes and 1 pair of sex chromosomes

• Humans
• Haploid of chromosomes 23
• Diploid 46
• Remember
• Have 23 pairs
• 1 of each pair came from mom
• 1 of each pair came from dad

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Dominant vs. Recessive Traits

• Each pair of chromosomes is referred to as
  HOMOLOGOUS CHROMOSOMES
• Have the same genes
• For each gene there can be 2 alleles (different
  forms)
• Look at picture below
• B brown eyes
• b blue eyes
• Brown is dominant so this persons phenotype
  would be brown eyes

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Dominant vs. Recessive Traits

• Incomplete Dominance
• Form of inheritance where heterozygous alleles
  are both expressed, combined phenotype
• Example a plant with white flowers and plant
  with red flowers has offspring with pink flowers
• Codominant
• Both alleles are expressed
• Example Blood types in humans
• If a person has the A allele and the B allele,
  then both A and B are expressed on the surface of
  the red blood cell

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Autosomal Traits

• Some Dominant Traits in Humans
• Widows peak
• Unattached earlobes
• Freckles

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Chromosomal Abnormalitiesresulting from
nondisjunction

• Down Syndrome (Trisomy 21)
• 3 21 chromosomes
• Sex Chromosomal Abnormalities
• Turner Syndrome XO
• Never reaches puberty
• Poly-X Syndrome (XXX)
• Tend to have learning disabilities
• Klinefelter Syndrome (XXY)
• Testes underdeveloped, long limbs, poor muscle
  growth
• Jacob Syndrome (XYY)
• Taller, speech and reading problems

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Sex-linked Genes

• Genes located on the sex chromosomes (23rd pair
  in humans)
• Examples
• Color-blindness
• Hemophilia
• Males only need 1 gene on X chromosome to have
  trait look at boy on far right

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Pedigrees

• Method that allows tracking of a genetic disorder
  within a family
• Circles Females
• Squares Males
• Affected individuals filled in
• Carriers half filled in

http//www.sciencegeek.net/Biology/review/Sem1Revi
ew.htm
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Pedigrees

• Patterns of inheritance
• Autosomal Dominant many children affected
• Autosomal Recessive few children affected
• X-linked recessive mostly males affected

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Pedigrees

• Patterns of inheritance
• Autosomal Dominant many children affected
• Autosomal Recessive few children affected
• X-linked recessive mostly males affected

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Pedigrees

• Patterns of inheritance
• Autosomal Dominant many children affected
• Autosomal Recessive few children affected
• X-linked recessive mostly males affected

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