Introduction to Genetics

1
Introduction to Genetics

• Chapter 11

2
The Work of Gregor Mendel

• Section 11.1

3
The Experiments of Mendel

• Heredity is the delivery of characteristics from
  parent to offspring.
• Scientific study of heredity is genetics.
• Austrian monk Gregor Mendel is the father of
  genetics.
• Used pea plants (a model system)

4
The Experiments of Mendel

• The Role of Fertilization
• Fertilization is when male/female reproductive
  cells join to make a new cell.
• Pea plants normally self pollinate true
  breeding
• Offspring identical
• Each plant had certain traits.
• These traits may vary between individuals.

5
The Experiments of Mendel

• Mendel crossed his true breeding plants to see
  how traits would be expressed.
• He studied 7 different traits.
• Each had two contrasting characters.
• Offspring of a cross between different parents
  are called hybrids.

6
The Experiments of Mendel

• Genes and Alleles
• Each original pair of plants is the P generation.
• Offspring are F1 first filial
• Genes are the factors (traits) passed from one
  generation to the next.
• Alleles are alternative forms of a gene.

7
The Experiments of Mendel

• Dominant and Recessive Alleles
• Principle of Dominance (Mendels 2nd Conclusion)
• Dominant trait will show if one allele present
  (masks other allele)
• Recessive need two alleles for trait to appear

8
Segregation

• Mendel didnt stop with crossing the parent
  plants.
• He thought Where did the recessive alleles go?
• He allowed all 7 kinds of plants to self
  pollinate.
• Called these the F2

9
Segregation

• The F1 Cross
• The F2 plants showed the recessive alleles!
• ¼ of the plants showed this trait.
• How could this be?
• At some point, the recessive allele had separated
  from the dominant.
• Another word for separationSEGREGATION
• Alleles segregate during the formation of gametes.

10
Segregation

• During gamete formation, the alleles for each
  gene segregate.
• Each gamete carries only one allele for each gene.