Pea Plants and Genetics

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Pea Plants and Genetics
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Mendel

• The field of genetics started with Gregor Mendel.
• Breeded pea plants and observed the results.
• Noticed that certain traits were inherited in the
  offspring generation.

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Pea Experiment

• Used pea plants because he could either
  self-pollinate or cross pollinate the plant

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Cont

• Peas have many different traits that can be
  observed. One example is flower color.

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Genetics Terms

• Mendel cross-bred 2 types of plants- the
  offspring are called hybrids.
• P Generation-the parent generation (red flower
  and white flower)
• F1 Generation- First offspring. (All red flowers
  
• F2 Generation-The offspring of a cross between
  two from the F1 generation.

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Results

• Mendel noticed that the F1 generation of all his
  crosses exhibited the same pattern of
  inheritance.
• Hypothesis Principle of segregation
• Pairs of genes separate during gamete formation
  (Meiosis)
• Now called alleles alternate forms of the same
  genes in a pair of homologous chromosome.

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Alleles

• Dominant Allele -The form of the gene that is
  expressed.
• Recessive Allele -The form of the gene that is
  overshadowed by the dominant allele.
• Dominant Allele is always a capital letter-D
• Recessive Allele is always a lower case letter of
  the same letter- d

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Punnett Squares

• To predict the outcome of a cross-breed-the
  alleles are separated out and a Punnett square is
  used.
• Example A purple flower is crossed with a white
  flower. Purple is the dominant color.

P P
p
p
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Using Punnett Squares

• By using a Punnett square, one is able to
  determine the genotype of the offspring.
• Genotype The genetic makeup of an organism.
• By knowing which alleles are dominant, one is
  able to determine the phenotype that aligns with
  each genotype.
• Phenotype the physical characteristics that a
  gene expresses.

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Genotype terms

• When an organism has two of the same allele types
  it is considered homozygous.
• Example RR Homozygous dominant
• rr Homozygous recessive
• When an organism has different allele types it is
  considered heterozygous.
• Example Rr Heterozygous

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Practice

• A round pea is crossed with a wrinkled pea.
  Round is dominant. What are the genotypes of the
  F1 generation?
• What are the genotypes of the F2 generation?