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This 5 page Class Notes was uploaded by Meghana Reddy on Friday January 15, 2016. The Class Notes belongs to 2130 at University of North Carolina - Charlotte taught by Dr.Benedetto in Spring 2016. Since its upload, it has received 333 views. For similar materials see BIOL 2130 - 004 in Biology at University of North Carolina - Charlotte.
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If Meghana isn't already a tutor, they should be. Haven't had any of this stuff explained to me as clearly as this was. I appreciate the help!
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Date Created: 01/15/16
Chapter 12 Patterns of Inheritance Study Questions 1. Describe the early viewpoints on inheritance. Before the 20 th century, these two concepts provided the basis for most thinking of heredity: ∙ Heredity occurs within species. ∙ Traits are transmitted directly from parents to offspring. 2. Look up “Blending Model” of inheritance and “Particulate Model” of inheritance. Compare these two. ∙ Blending Model: When these viewpoints were taken together, it led to a view of inheritance as resulting from a blending of traits within fixed unchanged species. According to this hypothesis, if a red flowered plant was crossed with a white flowered plant, it would produce offspring that are white colored flowers (an intermediate between the two). ∙ Particulate Model: Characteristics can be passed from generation to generation through “discrete particles” (genes). According to this theory, if a purpled colored flowering plant were to be crossed with a white colored flowering plant, an offspring of either of the color would be produced and not an intermediate of the two. This is the difference between the two models of inheritance. 3. Which model did Mendel’s work support? ∙ Mendel’s work supported the “particulate model” of inheritance since he worked with each trait as related to a particular gene. 4. What does “true breeding” mean? Offsprings that are produced from selffertilization that remains uniform in its genetic constitution, from one generation to the next. 5. What would have happened if Mendel did not use truebreeding strains? He would not be able to tell the recessive alleles that would show up in the F2 progeny. Since the F1 generation would have showed the dominant trait regardless, the only way to show the recessive alleles carry to the F2 is to have true breeding parents. 6. What is a monohybrid cross? Give an example. What is a dihybrid cross? Give an example. ∙ Monohybrid cross – Mating between two individuals with different alleles at one genetic locus of interest. ∙ Example: Rr × Rr: Heterozygous dominant round seeds. ∙ Dihybrid cross – Cross between two different lines (varieties, strains) that differ in two observed traits. ∙ Example: RrYy × RrYy: Heterozygous dominant round, yellow seeds. 7. Define the nomenclature “P”, “F1”, and “F2”. Explain their use in understanding inheritance. The parent plants in the experiments are referred to as the “P” generation. The offspring of the “P” generation are called the “F1” (filial) generation and the offspring of “F1” generation are called “F2” generation. 8. How do the terms gene, allele, homozygous, and heterozygous relate to the principle of segregation? Genes: Located on the chromosome and consist of DNA. Allele: Alternative forms of genes. Homozygous: Two alleles representing identical traits. Heterozygous: Two alleles with different traits. The principle of segregation: When Mendel crossed two heterozygous pea plants; he discovered that the traits in the offspring of his crosses did not always match the traits in the parental plants. This meant that the pair of alleles encoding the traits in each parental plant had separated or segregated from one another during the formation of the gametes. From this data Mendel formulated the Principle of segregation. 9. In a monohybrid cross, how do the events of meiosis explain Mendel’s law? The segregation of Chromosomes in Anaphase I of meiosis explains Mendel’s observation that each parent gives one allele for each trait at random to each offspring, regardless of whether the allele is expressed. 10. What is a pedigree? Describe the relationships that pedigree indicates. A pedigree is a chart of a person’s ancestors that is used to analyze genetic inheritance of certain traits especially diseases. Female Unaffected ⬤Female Affected ⬜Male Unaffected ⬛Male Affected Each generation is labeled with a roman numeral. Siblings are placed in birth order from left to right. 11. Explain the principle of independent assortment using your own words. During gamete formation, the segregation of alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair. 12. In a dihybrid cross, how does meiosis explain Mendel’s second law? The law of Independent assortment reflects that each homologous pair of chromosomes aligns independently of other chromosomes during Metaphase I of meiosis. 13. Use your own words to explain what a testcross is and how it is useful. A testcross is a mating between a homozygous recessive individual and an individual of unknown genotype. The genotype of the unknown parent can be deduced from the ratio of phenotypes in the F1 generation. 14. Distinguish between the different manners of inheritance in the table below by giving a description of the inheritance and an example: Form of Inheritance Description Example Polygenic A trait that is Height, skin color, controlled by many hair, eye color. genes. Codominance Produces phenotypes Roam fur in cattle. that are intermediate between or the combination of two traits. Incomplete The appearance in a Pink Roses dominance Heterozygote of a trait that is intermediate between either of the traits. Multiple Alleles Three or more forms ABO system of blood of a gene that can groups. occupy the same locus. Only two can be present in a single organism. Pleiotropy Occurs when one Phenylketonuria. gene influences two or more seemingly phenotypic traits. Epistasis Phenomenon that The gene for total consists of the effect baldness is epistasis to of one gene being those for blond hair or dependent on the red hair. presence of one or more ‘modifier genes’.
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