Mendelian Inheritance

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Mendelian Inheritance
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Mendelian Genetics

• Heredity
• Historical Aspects (before Mendel)
• Hereditary fluids
• blood relatives
• Gregor Mendel
• Austrian monk
• 1865
• Pea plants

• Pea plants
• Cross
• Statistics
• Quantitative work
• Looked at only 7 pea plant traits

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Mendels Work

• First found plants that bred true.
• Plant Anatomy
• Flower
• Pistil
• Stigma
• Style
• Ovary

• Stamen
• Anther
• Filament
• Self-pollination
• Cross-pollination

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Mendels Crosses

• Monohybrid Crosses
• Concerned with only one trait at a time.
• Produced hybrids.
• P generation
• F1 generation
• F2 generation

• Dihybrid Crosses
• Trihybrid Crosses

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Mendels Results and Conclusions

• Mendel concluded that
• 1. Each trait is controlled by 2 genes or
  alleles.
• 2. Some alleles are dominant, while other
  alleles are recessive.

• Important terms
• Homozygous
• Pure bred
• Heterozygous
• hybrid
• Phenotype
• genotype

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Mendels Conclusions

• 3. Law of SegregationDuring meiosis, each
  allele separates in an orderly manner from its
  partner, the two always go to different gametes.

• 4. Law of Independent AssortmentDuring
  Metaphase and Anaphase I of meiosis, the alleles
  for different traits segregate independently.
  This mixes chromosomes from your father and
  mother.

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More on Mendel

• Punnett Squares
• Probability
• Product Rule
• Test Cross
• Dihybrid and Trihybrid Crosses

• Incomplete DominanceNeither gene is completely
  dominant over the other. Snapdragons.
• CodominanceBoth alleles are expressed
  simultaneously.
• Human ABO blood type

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More on Mendel

• Mutiple allelessometimes more than 2 different
  alleles exist for a trait. (ABO blood type).
• Sometimes several gene pairs work together to
  bring about a trait.

• Polygenetic inheritance (skin color)
• Continous variation
• Epistatisa process whereby a pair of recessive
  alleles at one locus masks the effect of genes at
  other loci.(albinism)
• PleiotropyThe effect of one can can have many
  secondary effects. (cystic fibrosis)

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Mutations

• Wild type
• Mutant forms
• Point mutations
• Frameshift mutations
• Natural selection
• Biological evolution