New Title - Mrs. West's 7-1 Site



Mendel’s WorkIn the mid nineteenth century, a priest named Gregor Mendel tended a garden in a central European monastery. Mendel’s experiments in that peaceful garden would one day revolutionize the study of heredity. Heredity is the passing of physical characteristics from parents to offspring. Gregor Mendel was curious about the different forms of characteristics, or traits, of pea plants. Mendel’s work was the foundation of genetics, the scientific study of heredity.-16192526797000The picture below shows a pea plant’s flower. The flower’s petals surround the pistil and the stamens. The pistil produces female sex cells, or eggs. The stamens produce pollen, which contains the male sex cells, or sperm. A new organism begins to form when egg and sperm join in the process called fertilization?.?Before fertilization can happen in pea plants, pollen must reach the pistil of a pea flower. This process is called pollination. Pea plants are usually self-pollinating, meaning pollen from a flower lands on the pistil of the same flower. Mendel developed a method by which he cross-pollinated, or “crossed,” pea plants.Mendel crossed two pea plants that differed in height. He crossed purebred tall plants with purebred short plants. A? HYPERLINK "javascript:openGlossaryWnd('e_gcpurebred')" \o "Glossary Term, link opens in new window" purebred?organism is the offspring of many generations that have the same trait. These parent plants, the P generation, were purebred because they always produced offspring with the same trait as the parent. The offspring from this cross are the first filial (fil?ee ul) generation, or the F1?generation. The word?filial?comes from?filia?and?filius, the Latin words for “daughter” and “son.” When the plants in the F1?generation were full-grown, Mendel allowed them to self-pollinate. Surprisingly, the plants in the F2?(second filial) generation were a mix of tall and short plants. The shortness trait had reappeared, even though none of the F1?parent plants were short. Mendel counted the tall and short plants. About three fourths of the plants were tall, while one fourth were short.-3619504762500 In all of Mendel’s crosses, only one form of the trait appeared in the F1 generation. However, in the F2 generation, the “lost” form of the trait always reappeared in about one fourth of the plants.From his results, Mendel reasoned that individual factors, one from each parent, control the inheritance of traits. Today, scientists call the factors that control traits genes. The different forms of a gene are called alleles. An organism’s traits are controlled by the alleles it inherits from its parents. Some alleles are dominant, while other alleles are recessive. A dominant allele is one whose trait always shows up in the organism when the allele is present. A recessive allele is hidden whenever the dominant allele is present. A trait controlled by a recessive allele will only show up if the organism does not have the dominant allele.4686935168211500In Mendel’s cross, the purebred tall plant has two alleles for tall stems. The purebred short plant has two alleles for short stems. The F1 plants are all hybrids: (organisms that have two different alleles for the trait)—one allele for tall stems and one for short stems. Geneticists use a CAPITAL letter to represent a DOMINANT allele. For example, the allele for tall stems is represented by T. A lowercase version of the same letter is used for the recessive allele. So, the allele for short stems is represented by t. When a plant inherits two dominant alleles for tall stems, its alleles are written as TT. When a plant inherits two recessive alleles for short stems, its alleles are written as tt. When a plant inherits one allele for tall stems and one allele for short stems, its alleles are written as Tt.Mendel’s discovery was not recognized during his lifetime. In 1900, three different scientists rediscovered Mendel’s work. Because of his work, Mendel is often called the Father of Genetics.Name_________________________ Date:___________________ Mendel’s WorkGregor Mendel experimented with hundreds of pea plants to understand the process of_____________________.Match the term with its definition.TermDefinition 2. heredity 3. genetics 4. traitsThe scientific study of heredityPhysical characteristicsThe passing of traits from parents to offspringWhat is the process when sperm and egg join called? ________________________________In a flower, the female sex cells, or eggs, are produced by the________________________. Pollen, which contains the male sex cells, is produced by the _________________ ._________________________ is the process where pollen reaches the pistil of a flower. What are purebred organisms?106362525146000104457542672000-209550233045008. What is the P generation? ____________________________9. What does F in F1 offspring mean? Where does the word come from?_________________________________________________________________________________10. How many of Mendel’s plants after they were cross bred were tall? ________How many were short? __________11. What was Mendel’s hypothesis as to why this happened?_________________________________________________________________________________________________________________________________________________________12. What are the factors that control traits? ___________.13. What are the different forms of a gene are called? _______________________14. What is a dominant allele? _____________________________________________________________________________________________________________________________ 15. Circle the letter of each sentence that is true about alleles.Recessive alleles are never present when dominant alleles are present.Alleles are different forms of a gene.Dominant alleles always show up in the organism when the allele is present.Recessive alleles hide dominant alleles.16. True or False? Only pea plants that have two recessive alleles for short stems will be short. 17.What is a hybrid? ____________________________________________________________________________________________________________________________________Match the pea plant with its combination of alleles.Pea PlantCombination of Alleles 12. purebred short 13. purebred tall 14. hybrid tallTwo alleles for tall stemsOne allele for tall stems and one allele for short stemsTwo alleles for short stems15. A dominant allele is represented by a(n) __________________ letter.16. A recessive allele is represented by a(n) _____________________________________________________________letter.17. How would a geneticist write the alleles to show that a tall pea plant has one allele for tall stems and one allele for short stems? _____________________18.True or False? Some scientists during Mendel's time thought Mendel should be called the Father of Genetics. ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download