Genetics

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Genetics

• Chapter 11-1 11-2

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Genetics is the scientific study of heredity
(traits that are passed from parent to
offspring).
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The Work of Gregor Mendel

• Father of Genetics
• a teacher in a monastery
• cared for the garden where he worked
• was curious about how certain
• characteristics of pea plants were
• passed from parent plant to offspring
• changed biology forever

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Mendels Peas

• Mendel studied 7 different pea plants
  true-breeding traits.
• Looked at the following pea plant traits seed
  shape, seed color, seed coat color, pod shape,
  pod color, flower position, and plant height.

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What exactly is a trait??

• Trait a specific characteristic, that varies
  from one individual to another.
• True-breeding plants that were able to self
  pollinate and produce offspring that were
  identical to themselves.
• The offspring of crosses between parents with
  different traits are called hybrids.

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Mendels Pea Plant Traits
Seed Shape
Pod Color
Pod Shape
Seed Color
Seed Coat Color
Flower Position
Plant Height
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Mendel's Experimentation
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Genes

• In Mendels first generation of hybrid offspring
  the (F1) generation had the traits of only one
  parent (P). The other seemed to disappear.
• Mendel determined that
• Traits are inherited as a result of factors
  passed from parents to offspring
• We now know that these factors are genes

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Genes (contd.)

• Allele the different or alternate form of a
  gene.
• For example Flower color in pea plants has 2
  alleles purple and white

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Principle of Probability
- Used to predict traits of offspring produced by
genetic crosses
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Principle of Dominance

• States that some alleles are dominant and others
  are recessive.
• Dominant - a dominant allele is the trait that is
  always expressed.
• Written as a capital letter.
• Example plant height tall capital T.
• Recessive - a recessive allele is the trait that
  is covered unless there are two forms of the
  recessive allele.
• Written as a lower case letter.
• Example plant height lower case t.

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Principles of Dominance
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
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Law of Segregation

• During meiosis the two alleles separate from each
  other so that each gamete will carry only a
  single copy of each gene.
• Each F1 plant produces two types of gametes
• Example Pea Plant Height If the parent has two
  alleles, one for tall and one for short (Tt) so
  the gametes produced with have either T or t.

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Mendel in Summary
Gregor Mendel
concluded that
experimented with
which is called the
which is called the
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Genotype vs. Phenotype

• Phenotype is the physical characteristic of a
  trait of an organism.
• Example Tall or short
• Genotype is the genetic makeup of a trait.
• Example Tt, TT, or tt.

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Homozygous vs. Heterozygous

• Homozygous two identical alleles for a
  particular trait.
• Example TT or tt
• Heterozygous two different alleles for the same
  trait.
• Example Tt