MENDEL

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MENDELS LEGACY

• CH. 9

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Gregor Mendel (1823-1884)
The Father of Modern Genetics!
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Mendel taught natural science to High School
Students.

• Once he crossed peas and mice of different
  varieties for the fun of the thing

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• He determined several laws of inheritance....
• Mendels work became the foundation for Modern
  Genetics.

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Mendels peas

• MENDEL chose a common garden pea (Pisum) for his
  first experiments in hybridization

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Mendels Procedure

• Step ONE find plants that are pure for one
  trait (like height).
• Call them P1

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• Step TWO take opposites for the trait (like tall
  X short) cross pollinate/fertilize

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• Step 3 grow offspring and record results. (F1
  filial offspring)

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• Step 4 Allow self-pollination grow the
  grandchildren of P1. Call this group F2. Record
  results.

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• P1 HH (tall) X hh (short)
• Results All F1 grew tall!
• F1 X F1 F2
• Results, 3/4th peas were tall, 1/4th peas were
  short!

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Mendel discovered...

• ...some traits are masked...they are RECESSIVE
  and may skip generations.
• ...some traits are DOMINANT...they occur often in
  the population.

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• ...traits are determined by a pair of factors.
• Alleles

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Mendel determined...

• The pair of factors are sorted independently of
  each other.
• These factors are separated when the gametes are
  formed.

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HOW TO PLAY GENETICS GAMES

• Traits are expressed as letters of the alphabet.
• HH or hh
• Capital letters denote dominant traits

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• HH or hh are pure strains. They are called
  HOMOZYGOUS
• Hh are mixed strains....carriers of the recessive
  gene, but do not look recessive. They are called
  HETEROZYGOUS

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EXAMPLES

• H TALL
• h short
• HH homozygous tall
• hh homozygous short
• Hh heterozygous tall

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More vocabulary....

• genotype the letters we use to express traits
  genetic makeup
• phenotype what something looks like.

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Phenotypes
fat pod, smooth peas
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or...

• skinny pods, wrinkled peas