2.  Austrian monk in the mid-1800’s  Spent two years studying in the University of Vienna ◦ Was heavily influenced by two professors, one of whom was Christian Doppler  These years were important since he learned about the scientific method  Began breeding pea plants there  Great choice as they had many varieties, and had a short generation time

3.  In particular, he focused on inheritance  The variances found within the pea plants are called characters ◦ A variant on this character is a trait  Mendel could control mating  Reproductive organs are in the flowers, and each plant has both parts ◦ Pollen produced in stamens ◦ Eggs produced in carpel

5.  Achieved cross-pollination by removing immature stamens from one plant, then transferred sperm-bearing pollen from another  Zygote develops into plant embryo encased in a pea  He tracked characteristics that had only two variations (such as colour)  Also used plants that, over many generations of self pollination, produced the same colour  Called these true-breeding

6.  Mendel studied seven pea plant characters, each with two contrasting traits  He crossed plants with each of the seven contrasting characters and studied their offspring  Each original pair of plants is the P (parental) generation  The offspring are called the F 1, or “first filial,” generation

7.  The offspring of crosses between parents with different traits are called hybrids  The F 1 hybrid plants all had the trait of only one of the parents

8. Mendel’s F 1 Crosses on Pea Plants

9.  Mendel's first conclusion was that biological inheritance is determined by factors that are passed from one generation to the next  Today, scientists call the factors that determine characteristics genes  Each of the characters Mendel studied was controlled by one gene that occurred in two contrasting forms that produced different characters for each trait  The different forms of a gene are called alleles  Mendel’s second conclusion is called the principle of dominance

10.  The principle of dominance states that some alleles are dominant and others are recessive  An organism with a dominant allele or trait will always exhibit that form  An organism with the recessive allele will exhibit that form only when the dominant allele is not present

11.  Mendel crossed the F 1 generation with itself to produce the F 2 (second filial) generation  The traits controlled by recessive alleles reappeared in one fourth of the F 2 plants

12. Copyright Pearson Prentice Hall  Mendel's F 2 Generation P Generation F 1 Generation Tall Short F 2 Generation

13.  Mendel assumed that a dominant allele had masked the corresponding recessive allele in the F 1 generation  The trait controlled by the recessive allele showed up in some of the F 2 plants  The reappearance of the trait controlled by the recessive allele indicated that at some point the allele for shortness had been separated, or segregated, from the allele for tallness

14.  When each F 1 plant flowers and produces gametes, the two alleles segregate from each other so that each gamete carries only a single copy of each gene  Therefore, each F 1 plant produces two types of gametes—those with the allele for tallness, and those with the allele for shortness

15.  Alleles separate during gamete formation