1. Mendelian Genetics 1

2. Gregor Mendel (1822-1884) Father of genetics Austrian Monk Between 1856 – 1863 he studied ~28,000 pea plants Importance of his work not realized until 20 th century, ~20 years after death 2

3. Mendel’s Experiments 3

4. The Peas Advantages of Pea Plants: – Grown in small areas – distinct heritable features – Each feature has two variants – Lots of offspring – Can self-fertilize or cross fertilize 4

5. Reproduction in Flowering Plants Pollen (produced by stamen) contain sperm Ovary contains egg Pollen grows tube down style to carry sperm to egg Self-fertilization - sperm and egg from same flower Cross-fertilization - sperm and egg from different flower 5

6. His Experiments First created true- breeding peas by allowing them to self- fertilize True breeding = only produces offspring with one specific trait 6

7. His Experiments Then, he cross-fertilize (hybridized) two contrasting, true-breeding varieties (P 1 generation - parent) Offspring is the F 1 Generation – first filial Then allowed the F 1 hybrids to self-pollinate to produce an F 2 generation – 2 nd filial 7

8. His Experiments 8 P 1 Generation F 1 Generation All tall F 1 Generation F 2 Generation 3 tall, one short

9. His Experiments 9 Results: F 1 generation: all dominant phenotypes F 2 generation: 3:1 ratio of dominant to recessive phenotypes

10. His Experiments Created three Laws of Inheritance – Law of Dominance – Law of Segregation – Law of Independent Assortment 10

11. Mendel’s Laws of Inheritance 11

12. Law of Dominance In a cross of true-breeding parents, only one form of the trait will appear in the next generation The apparent trait is dominant, the other is recessive 12

13. Law of Segregation The pair of factors (alleles) is segregated, or separated, during formation of gametes (sperm and egg) 13

14. Law of Independent Assortment Factors (alleles) for different traits are distributed in gametes independently of each other 14

15. Applying Mendel’s Laws – Punnet Squares Two types – used to show expected genotype of offspring Monohybrid – 2 gametes from each parent – 2x2 grid Dihybrid – 4 gametes from each parents – 4x4 grid 15

16. Applying Mendel’s Laws – Test Cross A mating between an organism with unknown genotype and a homozygous recessive organism Example: – Mice can either be brown (B) or white (b). You have a mouse with a brown coat. – Can be BB or Bb – If Bb: offspring half brown/half white – If BB: offspring all brown 16