11-1 The Work of Gregory Mendel

1. Flora Biology I 11-1The Work of Gregory Mendel

2. Genetics • Genetics – the study of heredity • Essential to understanding biology

3. Mendel • Mendel knew the following: • Each part of each flower produces pollen (anther) • Other portions produce female reproduction cells • The two join and fertilization occurs • Gametes – sex cell • Fertilization – male and female reproduction cells join to form a new cell • True-breeding – if allowed to self-pollinate, they would produce offspring identical to themselves

4. Genes and Dominance • Mendel studied plant traits • Trait – specific characteristic of an organism • Ex: seed color, plant height, etc. • Mendel studied 7 traits: • Seed shape • Seed color • Seed coat • Pod shape • Pod color • Flower position • Plant height

5. Cont. • Mendel crossed plants with these seven contrasting traits and studied their offspring • Parents – called “P” generation • Offspring – called “F1” generation A cross between parents with different traits are known as hybrids

6. Mendel’s Two Conclusions • Biological inheritance is determined by factors that are passed on from one generation to the next • These traits are called genes • Genes – sequence of DNA that codes for a specific protein thus determining the trait • Some genes have contrasting forms called alleles • Alleles – one of a number of different forms of a gene

7. Cont. Mendel’s Two Conclusions • The principal of dominance states that some alleles are dominant and others are recessive • An organism with a dominant allele for a specific trait will always exhibit that form of that trait. • Recessive alleles will only exhibit that trait when the dominant allele is absent • Ex: Mendel’s Experiment

8. Segregation • Did the alleles present in the P generation disappear from the F1 generation? • Mendel allowed 7 kinds of F1 hybrid plants to self-pollinate producing an F2 generation • See page 265

9. Law of Segregation • when any individual produces gametes, the copies of a gene separate, so that each gamete receives only one copy. A gamete will receive one allele or the other • Each F1 plant produces two types of gametes • Ex: Tt x Tt