BIO 10 Lecture 10

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BIO 10 Lecture 10

• REPRODUCTION
• CHROMOSOMES AND HEREDITY

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An Introduction to Mendel and His Peas1856-1863

• Research in Brno, Czech Republic
• Observed the inheritance patterns of seven
  inherited physical characteristics in several
  generations of pea plants and applied mathematics
  to discover the two basic laws that govern their
  behavior
• Did his work before chromosomes (1880's) or DNA
  (1950's) had been discovered
• Was a monk who grew his pea plants in the
  monastery garden

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Mendel's First Law Law of Segregation

• -Genetic information is carried by discrete
  entities (genes)
• Complex organisms carry two copies of each gene
  but pass only one copy to each gamete
• Each gene controls a single trait (e.g. seed
  color) but different forms of the same gene
  (alleles) can confer different expressions of
  that trait (e.g. yellow vs. green seeds)

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Law of Segregationcontinued...

• An individual that carries two of the same allele
  for a gene is homozygous. An individual that
  carries two different alleles for a gene is
  heterozygous.
• In a heteroygote, only one allele is physically
  expressed this allele is dominant (A) over the
  unexpressed, recessive (a) allele.

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Genotype vs. Phenotype

• The phenotype of an organism is its physical
  appearance or behavior
• This is all Mendel could actually study
• "The mature seed is yellow" phenotype
• The genotype of an organism is its genetic
  make-up
• Mendel inferred how genes behaved based on his
  observations of the patterns in which phenotypes
  were inherited
• Yy genotype

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Mendel's First Law and Meiosis
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Mendel's Second Law Law of Independent
Assortment

• - When two genes and their alleles are followed
  through a genetic cross, the alleles of the two
  different genes are randomly shed into the
  gametes without regard to one another - i.e.
  independently
• Therefore, a dihybrid will create 4 different
  types of gametes in equal proportions AB, ab,
  Ab, and aB

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Meiosis and the Law of Independent Assortment
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Short Review of Lecture 10

• How many gametes, and what types, can be produced
  by a pea plant with the genotype PP? How about
  Pp? pp?
• How many gametes, and what types, can be produced
  by a pea plant with the genotype PpTt? How about
  PPTt?
• How many gametes, and what types, can be produced
  by a pea plant with the genotype PpTtYy? How
  about PPTtYy?