6 3 Mendel and Heredity KEY CONCEPT Mendels

6. 3 Mendel and Heredity KEY CONCEPT Mendel’s research showed that traits are inherited as discrete units.

6. 3 Mendel and Heredity 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 1800 s by Gregor Mendel. “Father of Genetics”

6. 3 Mendel and Heredity 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

6. 3 Mendel and Heredity Many people thought that traits were blended. • As in your traits were a perfect mixture of your mother’s and father’s traits.

6. 3 Mendel and Heredity But this failed to explain how certain traits remained with out being “diluted”

6. 3 Mendel and Heredity 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

6. 3 Mendel and Heredity 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

6. 3 Mendel and Heredity • 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.

6. 3 Mendel and Heredity What did Mendel find in his first Generation (F 1) P p p Genotype: Phenotype: P

6. 3 Mendel and Heredity What did Mendel find in his first Generation (F 1) P p Pp Pp Genotype: Pp Phenotype: 100% Purple Flowers

6. 3 Mendel and Heredity What did Mendel find in his second Generation (F 2) P P p Genotype: Phenotype: p

6. 3 Mendel and Heredity What did Mendel find in his second Generation (F 2) P p P PP Pp pp Genotype: PP, Pp, pp Phenotype: 75% Purple flowers, 25% white flowers

6. 3 Mendel and Heredity • Mendel allowed the resulting plants to self-pollinate. P F 1 F 2 – Plants in generation 1 (F 1) were all purple – Most plants ( ¾ )in generation 2 (F 2) were purple, but white began to appear in some offspring (¼ )

6. 3 Mendel and Heredity • Mendel observed patterns in the first and second generations of his crosses.

6. 3 Mendel and Heredity • Mendel drew three important conclusions. 1. Traits are inherited as discrete units/ individually. (genes) purple LAW OF SEGREGATION 2. Organisms inherit two copies of each gene, one from each parent. 3. The two copies separate during gamete formation (Meiosis). white