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Exploring Mendelian Genetics

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Exploring Mendelian Genetics Two trait Crosses 11.3 Dihybrid crosses Two-Factor Cross Mendel crossed pure-breeding plants for two traits Round, Yellow x wrinkled ... – PowerPoint PPT presentation

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Title: Exploring Mendelian Genetics


1
Exploring Mendelian Genetics
  • Two trait Crosses
  • 11.3

2
Dihybrid crosses
  • All of the crosses discussed so far have involved
    only a single trait.
  • Ex. Tt
  • However, Mendel also conducted crosses that
    examine the inheritance of two different traits.
  • He wondered if both traits would always appear
    together or if they would be expresses
    independently of each other.

3
Two-Factor Cross
  • Mendel crossed pure-breeding plants for two
    traits
  • Round, Yellow x wrinkled, green
  • RRYY x rryy
  • All F1 offspring produced were Round, Yellow
  • Yellow is dominant to Green
  • Round is dominant to wrinkled
  • Genotype of F1 offspring is RrYy

4
A dihybrid cross involves two traits.
  • Mendels dihybrid crosses with heterozygous
    plants ( F1 generation) yielded a 9331
    phenotypic ratio for the F2 generation.
  • Mendels dihybrid crosses led to his second
    law,the law of independent assortment.

5
  • The law of independent assortment states that
    allele pairs separate independently of each other
    during meiosis.
  • Independent assortment helps account for the many
    genetic variations observed in plants, animals,
    and other organisms.

6
Dihybrid Cross
RrYy x RrYy
7
Dihybrid Cross
8
Dihybrid Cross
9
Summary of Mendels Principles
  • Principle of Heredity
  • Inheritance of biological characteristics is
    determined by individual units known as genes.
    Genes are passed from parents to offspring.
  • Principle of Dominance
  • In cases in which two or more alleles of the gene
    for a single trait exist, some gene forms may be
    dominant and others recessive.

10
Summary of Mendels Principles
  • Principle of Segregation
  • In most sexually reproducing organisms, each
    adult has two copies of each gene- one from each
    parent. These genes are segregated from each
    other when gametes are formed.
  • Principle of Independent Assortment
  • The alleles for different genes usually segregate
    independently from one another.
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