Mendel

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Mendels InvestigationsMendelian Genetics
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Gregor Mendel

• Lived in a monastery in Vienna during the 1800s
  (monk)
• Worked primarily with pea plants
• His work changed biology forever with respect to
  Genetics
• Father of Genetics

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Mendels Experiment

• A. Used pure bred pea plants (same alleles from
  each parent)
• B. Most noted for his use of math to make
  conclusions

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Experiment and Observations

• P1 Pure Tall x Pure Short
• ?
• F1 Hybrid Tall
• ?
• Hybrid Tall x Hybrid Tall
• ?
• F2 ¾ Tall ¼ Short

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Mendel drew three important conclusions.

• Traits are inherited as discrete units. DO NOT
  BLEND
• Organisms inherit two copies of each gene, one
  from each parent.
• The two copies segregate during gamete formation.

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Alleles

• Alleles are passed from parent to offspring
• One from mom and one from dad.
• Dominant alleles are the expressed or observed
  traits ( brown eyes )
• Recessive alleles are the disappearing or
  non-expressed traits (blue eyes)

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• Each parent donates one allele for every gene.
• Homozygous describes two alleles that are the
  same at a specific location.
• Heterozygous describes two alleles that are
  different at a specific location.

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Phenotype vs Genotype

• Phenotype is the way an organism appears
• Brown hair with blue eyes, tall, thin, etc.

• Genotype is the genetic combination for the
  organism. (BB, Bb, bb)

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• Heterozygous Example allele from mom codes for
  blue eyes and the allele from dad codes for brown
  eyes.
• Homozygous Example both alleles code for blue
  eyes
• So, the genotype for a heterozygous brown eyed
  offspring would be Bb for example.

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Lets Practice

• Tell whether the following are heterozygous or
  homozygous
• Tt Gg
• TT gg
• Hh GG
• Bb ff
• bb

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Mendels Laws

• 1. Law of Segregation
• Genes separate when gametes form- sex
  cells get one complete set of chromosomes

• Law of Dominance
• When two alleles in a gene pair are
  different, one allele can control the trait while
  the other can be hidden

• Law of Independent Assortment
• Gene pairs separate randomly and independent of
  each other during meiosis
• Important when dealing with the inheritance of
  more than one trait.

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Punnett Square

• Used to help solve genetics problems