The Work of Gregor Mendel

1
The Work of Gregor Mendel

• Chapter 11, Section 1

2
Chapter 11 Introduction to Genetics

• Genetics is the scientific study of heredity, or
  the passing of characteristics from one organism
  to another

3
Gregor Mendel (1822-1884)

• An Austrian monk who used a scientific approach
  to study inheritance
• He is considered the Father of Genetics
• There was no knowledge of genes or DNA at the
  time
• He studied inheritance patterns in pea
  plantsWhy?
• Contrasting traits or characteristics
• Reproduce sexually, quickly, and have many
  offspring
• Accessible and easy to handle

4
Controlled Reproduction

• Stamen(?) produces pollen
• Carpel/Pistel(?) produces ovules (eggs)
• Removing immature stamen prevents
  self-fertilization

5
Sexual Reproduction in Plants

• Fertilization Occurs when male and female sex
  cells join
• Cross-pollination Pollen from one plant
  fertilizes(pollinates) egg of another plant
• Self-pollination Pollen and eggs come from the
  same flower

6
Mendels 7 Traits of Pea Plants
7
Mendels Experiments

• Mendel identified stocks of plants that were
  TRUE-BREEDING for a particular trait
• Tall Plant ? self-pollination ? All Tall
  Offspring
• Mendel crossed two true-breeding plants with
  contrasting characteristics
• (ex purple flowers and white flowers)
• He called them the P generation (for Parental)
• What do you think the offspring looked like?

8
Mendels F1 Generation
F1 (for Filial) or son in Latin!

• The offspring were
• 100 Purple Flowering
• Mendel repeated this experiment and observed
  similar results with all 7 of the traits he
  studied!
• He called the F1 generation HYBRIDS

9
A Second Generation

• Mendel let the F1 generation self-pollinate and
  created a F2 generation
• The white-flowering trait reappeared in the 2nd
  Generation!!
• (3 Purple to 1 White)

10
Mendels Principles (in modern terms)

• Traits are passed from one organism to another by
  units called genes. There are different forms of
  genes called alleles.
• Ex Gene height
• Alleles tall, dwarf
• Genes are inherited in pairs, one allele from
  each parent
• Homozygous identical alleles
• Heterozygous different alleles
• In a hybrid, only the dominant allele (T) will be
  expressed (or seen). The other allele is
  recessive (t).
• Alleles segregate (separate) from each other
  during gamete formation and rejoin during
  fertilization to make the offspring

11
Principle of Segregation
What process segregates the alleles during gamete
formation???
12
MEIOSIS!!