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Study_Guide_for_Chapter_13_14_and_15(2)

Study_Guide_for_Chapter_13_14_and_15(2) - Study Guide for...

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Study Guide for Chapter 13 1. What were the positive advantages of Mendel’s experimental system and why is it important to the success of an experiment to choose an appropriate experimental system? 2. Know the genetics vocabulary: true-breeding, homozygous, heterozygous, dominant, recessive, alleles, genotype, phenotype, F 1 generation, test cross, pedigree, genetic recombination, wild type, linkage, nondisjunction True-breeding : transmitting unchanged from generation to generation. Pea plants with white flowers, for example, when crossed with each other, produced only offspring with white flowers, regardless of the number of generations. Homozygous – When two haploid gametes containing exactly the same allele of a factor fuse during fertilization to form a zygote, the offspring that develops from that zygote is said to be homozygous. Heterozygous – When two haploid gametes contain different alleles, the individual offspring is heterozygous. Dominant – Mendel referred to the form or trait expressed in the F1 plants as dominant. Recessive – to the alternative form that was not expressed in the F1 plants as recessive. Alleles – In modern terms, the alternative forms of a factor, leading to alternative forms of a character are called alleles. Genotype – To distinguish between the presence of an allele and its expression, modern geneticists refer to the totality of alleles that an individual contains as the individual’s genotype. Phenotype – and to the physical appearance of that individual as its phenotype. F1 Generation – Employing these simple symbols, we can now go back and reexamine the crosses Mendel carried out. Because a white flowered parent (pp) can produce only p gametes, and a pure purple flowered parent (PP) can produce only P gametes, the union of an egg and a sperm from these parents can produce only heterozygous pP offspring in the F1 generation. They will all be purple. Test Cross – To test his hypothesis further, Mendel devised a simple and powerful procedure called the testcross. Consider a purple flowered plant. It is impossible to tell whether such a plant is homozygous or heterozygous siply by looking at its phenotype. To learn its genotyple, you must cross it with some other plant. What kind of cross would prvide the answer? If you cross it with a homozygous dominant individual, all of the progeny will show the dominant phenotype whether the test plant is homozygous or heterozygous.
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Pedigree A consistent graphical representation of matings over multiple generations for a particular trait. Genetic recombination –Crossing over creates new combinations of genes, and is thus a for of genetic recombination. Wild Type By convention, the most common allele of a gene is often denoted with the symbol “+” and is designated as wild type.
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