KEY CONCEPT Mendel’s research showed that traits are inherited as discrete units.

Genetics: is the study of biological inheritance patterns and variation in organisms. The groundwork for much of our understanding was laid down in the middle of the 1800s by Gregor Mendel. “Father of Genetics”

When we think of how offspring resemble or differ from their parents, we refer to specific traits. Traits: are distinguishing characteristics that are inherited. Ex: eye color, leaf shape, tail length

Many people thought that traits were blended. As in your traits were a perfect mixture of your mother’s and father’s traits.

But this failed to explain how certain traits remained with out being “diluted”

Mendel’s data revealed patterns of inheritance. Mendel made three key decisions in his experiments. use of purebred plants control over breeding observation of seven “either-or” traits Purebred: genetically uniform

Pea shape: round OR wrinkled Pea color: green OR yellow Either/Or traits Pea shape: round OR wrinkled Pea color: green OR yellow Pod shape: smooth OR constricted Pod color: green OR yellow Plant height: tall OR short Flower color: purple OR white Flower position: axial OR terminal

Mendel used pollen to fertilize selected pea plants. interrupted the self-pollination process by removing male flower parts Mendel controlled the fertilization of his pea plants by removing the male parts, or stamens. He then fertilized the female part, or pistil, with pollen from a different pea plant.

P P p p What did Mendel find in his first Generation (F1) Genotype: Phenotype:

P P p Pp Pp p Pp Pp What did Mendel find in his first Generation (F1) Genotype: Pp Phenotype: 100% Purple Flowers

P p P p What did Mendel find in his second Generation (F2) Genotype: Phenotype:

P p P PP Pp p pp Pp What did Mendel find in his second Generation (F2) Genotype: PP, Pp, pp Phenotype:75% Purple flowers, 25% white flowers

P F1 F2 Mendel allowed the resulting plants to self-pollinate. Plants in generation 1 (F1) were all purple Most plants ( ¾ )in generation 2 (F2) were purple, but white began to appear in some offspring (¼ ) P F1 F2

Mendel observed patterns in the first and second generations of his crosses.

Mendel drew three important conclusions. purple white Traits are inherited as discrete units/ individually. (genes) LAW OF SEGREGATION 2. Organisms inherit two copies of each gene, one from each parent. 3. The two copies separate during gamete formation (Meiosis).