Ch9 Genetics

Ch9 Genetics - Chapter 9- Genetics 1. Mendel's Experiments...

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Chapter 9- Genetics 1. Mendel’s Experiments : Gregor Mendel: Austrian monk who worked ~ 1850-1870 a. What Mendel did i. He grew garden peas [9.3] ii. He controlled parentage: 1. Self-fertilized (natural) 2. Cross fertilized- pollen from different variety (artificial) [9.4] iii. He identified true-breading varieties iv. He crossed varieties that differed only in one characteristic to make hybrid [9.4] 1. Parents : P generation 2. Offspring: F1 generation v. He inbred the F1 (F1 mated with F1 or self ferrilized) 1. To make F2 generation [9.6] vi. He counted the # of each phenotype b. Mendel’s Law of Segregation i. One phenotype only in F1=dominant trait 1. Recessive trait is “hidden” in F1 and reappears in F2 [9.6] 2. F2 had 3:1 ration of dominant to recessive phenotypes 3. Therefore two “factors” (genes) from parents determine phenotypes a. Alternative forms of genes= alleles b. Genotype= actual alleles present 4. True-breeding peas are homozygous- both alleles same (both dominant or both recessive) 5. When gametes form, the two alleles “segregate” into different gametes [9.6] a. = Mendel’s Law of Segregation- each parent gives 1 allele 6. F1 hybrid gets two different alleles(to offspring) heterozygous a. But only dominant allele is “expressed” in hybrid (uppercase letter)
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7. Two different alleles of F1 hybrid go into different gametes 8. Gametes combine randomly to form zygote, following Laws of Probability a. Punnett Square b. Recessive trait (homozygous recessive genotype ) reappears in F2 9. Alleles are on homologous chromosomes a. Law of Segregation due to Anaphase 1 10. Examples of monohybrid crosses a. Look at notes! b. Ex. Eye color i. Bb=blue eyes “pigmentless” ii. B_ = pigmented eyes (brown, hazel, ets) iii. Hazel eyed mom X blue eyed dad child with blue eyes iv. What is Mom’s genotype? 1. B_ X bb
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This note was uploaded on 03/27/2008 for the course BIOL 113 taught by Professor Any during the Spring '07 term at Texas A&M.

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Ch9 Genetics - Chapter 9- Genetics 1. Mendel's Experiments...

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