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

6.3 Mendel and Heredity Important Terms Heredity-the passing of characteristics form parents to offspring. Traits-characteristics that are inherited and have variation. RULE of DOMINANCE-in a heterozygote, the dominant trait will prevent the recessive trait from being expressed. The recessive trait is present and the allele can be passed to next generation. Tt, Bb, Ss- heterozygous, hybrid TT, BB- homozygous dominant, pure bred, true breeding tt,bb,ss-homozygous recessive, pure bred, true breeding

6.3 Mendel and Heredity Genotype- allele (gene factor) combination Expected results, probability Phenotype- observed, expressed traits, physical characteristics. Gamete- sex cell Zygote- fertilized egg Test cross- mating of the sex cells and producing truebreeding or hybrids

6.3 Mendel and Heredity Law of Segregation- The two alleles for a trait must separate when the gametes are formed; therefore, each parent only passes one allele for each trait. After fertiliztion, the offspring has inherited one allele (gene factor) from each parent.

6.3 Mendel and Heredity Mendel laid the groundwork for genetics. Traits are distinguishing characteristics that are inherited. Genetics is the study of biological inheritance patterns and variation. Gregor Mendel showed that traits are inherited as discrete units. Many in Mendel’s day thought traits were blended.

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

6.3 Mendel and Heredity

Mendel used pollen to fertilize selected pea plants. 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. –Cross mating of two organisms –P1-(purebred) generation crossed to produce F 1 generation –interrupted the self-pollination process by removing male flower parts

6.3 Mendel and Heredity Mendel allowed the resulting plants to self-pollinate. –Among the F 1 generation, all plants had purple flowers –F 1 plants are all heterozygous –Among the F 2 generation, some plants had purple flowers and some had white

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

6.3 Mendel and Heredity Results--3:1 ratio or 75%/25% phenotype Mendel conclusions: Traits are inherited as discrete units –The law of Segregation. –Organisms inherit two copies of each gene, one from each parent. –The two copies segregate during gamete formation. purplewhite