My_Ch14_lecture_MendelianGenetics(2009030423480871)

My_Ch14_lecture_MendelianGenetics(2009030423480871) -...

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Chapter 14—Mendelian Genetics Purpose —to understand the basic concepts of Mendelian Genetics, the relationship between genotype and phenotype, and the basic patterns of inheritance. (AP Bio Major Themes: I—Science as a Process (Mendel’s experimental methods and conclusions), IV— What you MUST know from Ch 14: Law of Segregation Test cross Law of Independent Assortment Dominance, codominance, incomplete dominance Multiple alleles Pleiotropy Epistasis Polygenic inheritance Multifactorial Recessive inherited disorders Dominantly inherited disorders Fetal testing Gregor Mendel ’s experimental work with pea plants formed the basis of modern genetics. He used quantitative experiments to test his hypothesis, made astute observations, and used logical thought to develop explanations for his observations. (Science as a Process) Pea plants were chosen because there were many traits that could be observed over many generations. Could manipulate cross-pollination to mate specific plants with specific traits.
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Self-pollination (usual mode of reproduction) allowed him to start his experiments with true- breeding plants. Some genetics vocab: Trait = a particular variant (type) of inherited characteristic Monohybrid cross = mating that tracks 1 trait Dihybrid cross = mating that tracks 2 different traits Gene = segment of DNA on a chromosome that contains the code or instructions for a particular trait Allele = 1 of several varieties or alternative forms of a gene Locus = location of a gene on a particular chromosome. Every gene has a unique locus. Genotype = genetic makeup of an organism (what genes, alleles it has) Phenotype = physical appearance of an organism; results from (depends on) the genotype I’m not going to repeat all information on the various crosses in the book (so, read it!), nor P, F 1 , F 2 generations. .. this should be review; what you need to know are the characteristic ratios for each type of cross. Classic Monohybrid cross : P generation = PP X pp homozygous dominant x homozygous recessive F 1 = ½ Pp + ½ pp 1:1 ratio p p alleles (gametes)
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P P Now, cross the 2 heterozygous F 1 offspring: P p P p F 2 generation = ¼ PP + ½ Pp + ¼ pp Genotype = ½ homozygous dominant ½ heterozygous dominant ¼ homozygous recessive Ratio = 1:2:1 Phenotype = ¾ dominant trait expressed ¼ recessive trait expressed Ratio = 3:1 How did Mendel explain these findings? 1.Different alleles (alternative versions of genes) account
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This note was uploaded on 09/29/2011 for the course BIO 020.152 taught by Professor Pearlman during the Fall '08 term at Johns Hopkins.

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My_Ch14_lecture_MendelianGenetics(2009030423480871) -...

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