* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 11 Section 11_1 The Work of Gregor Mendel
Survey
Document related concepts
Genetic engineering wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Genetically modified crops wikipedia , lookup
Transgenerational epigenetic inheritance wikipedia , lookup
Genomic imprinting wikipedia , lookup
Population genetics wikipedia , lookup
Designer baby wikipedia , lookup
History of genetic engineering wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Genetic drift wikipedia , lookup
Transcript
Chapter 11: Introduction to Genetics 11.1 – The Work of Gregor Mendel Mr. M. Varco Saint Joseph High School The Experiments of Mendel • What is inheritance? The Experiments of Mendel • Every living thing has a set of characteristics inherited from its parent or parents. • The delivery of characteristics from parent to offspring is called heredity. • The scientific study of heredity, known as genetics, is the key to understanding what makes each organism unique. The Experiments of Mendel • The modern science of genetics was founded by an Austrian monk named Gregor Mendel. • Mandel carried out his work using garden peas because a single pea plant could produce hundreds of offspring in a short period of time. The Experiments of Mendel The Role of Fertilization • Mendel knew that the male part of each flower makes pollen, which contains sperm - the plant’s male reproductive cell. The Experiments of Mendel The Role of Fertilization • Mendel knew that the female portion of each flower produces reproductive cells called eggs. The Experiments of Mendel The Role of Fertilization • During sexual reproduction, male and female reproductive cells join in a process called fertilization, to produce a new cell. The Experiments of Mendel The Role of Fertilization • Pea flowers are normally self-pollinating, meaning that sperm cells fertilize egg cells from within the same flower. • A plant grown from seed produced by self-pollination inherits all of its characteristics from a single parent. The Experiments of Mendel The Role of Fertilization • Mendel’s garden had several “true-breeding” pea plants, meaning they were self-pollinating and would produce genetically identical offspring. • A trait is a specific characteristic of an individual, and may vary from one individual to another. The Experiments of Mendel The Role of Fertilization • Mendel decided to “cross” his stocks of true-breeding plants - he caused one plant to reproduce with another plant. The Experiments of Mendel The Role of Fertilization • He prevented self-pollination by cutting the pollen-bearing male parts of each flower, and dusting pollen from another plant onto the female part of that flower. The Experiments of Mendel The Role of Fertilization • This process, known as cross-pollination, produced a plant that has two different parents. • Cross pollination allowed Mendel to breed plants with traits different from those of their parents and then study the results. The Experiments of Mendel The Role of Fertilization • Mendel studied 7 different traits of pea plants, each of which had two contrasting characteristics. • The offspring of crosses between parents with different traits are called hybrids The Experiments of Mendel • When doing genetic crosses, we called each original pair of plants the parental, or P generation. • Their offspring are called the F1, or filial generation. The Experiments of Mendel Conclusion #1 • An individual’s characteristics are determined by factors that are passed down from one parental generation to the next. • These “factors” are known as genes The Experiments of Mendel Conclusion #1 • Each trait is controlled by a single gene that occurred in two different forms. These forms are called alleles. • The expression of a trait is dictated by the combination of alleles for a particular gene. The Experiments of Mendel Conclusion #2 • The Principle of Dominance states that some alleles are dominant and others are recessive. • An organism with at least one dominant allele for a particular trait will express that form of the trait. The Experiments of Mendel Conclusion #2 • An organism with a recessive allele for a particular form of a trait will exhibit that form only when the dominant allele for the trait is absent. Segregation • What happened to the recessive alleles from the F1 generation? • To determine what happened to the recessive alleles, Mendel allowed all 7 kinds of F1 hybrids to self-pollinate. • The offspring of an F1 cross are called the F2 generation. Segregation • The traits controlled by the recessive allele reappeared in the second generation. • Approximately 25% of the F2 plants showed the trait controlled by the recessive allele Segregation • Mendel assumed that a dominant allele had masked the recessive allele in the F1 generation. • The reappearance of the recessive allele in the F2 generation indicated that at some point, the allele for shortness separated from the allele for tallness. • How did this segregation occur? Segregation • Mendel assumed that the two alleles segregated from each other during the formation of the sex cells, or gametes. • During gamete formation, the two alleles for each gene segregated from each other, so that each gamete carries only one allele for each gene. Segregation • A capital letter represents a dominant allele; a lower-case letter represents a recessive allele. • Whenever a gamete carrying the “t” allele paired with the other gamete that carried the “t” allele to produce the F2 plant, that plant was short.