ch2 - Chapter 2 Hereditary traits = characters...

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Chapter 2 Hereditary traits = characters: characteristics of an individual that are transmitted from one generation to another; under the control of genes (= Mendel’s “factors”) Genes provide potential for developing a particular phenotype, which also depends on interactions w/ other genes and environmental influences o Thus, same genotype can produce different phenotypes, and vice versa Mendel’s experiment o Garden pea good model – easy to grow, short reproductive cycle, lots of offspring o Self-fertilization = selfing: how garden peas usually reproduce Opposite: cross-fertilzation = cross o Worked w/ true-breeding = pure-breeding strains o Garden pea characteristics studied Gray seed coat w/ purple flower vs white seed coat & flower Yellow vs green seed color Smooth vs wrinkled seed shape Green vs yellow pod color Inflated vs pinched pod shape Tall vs short stem height Axial vs terminal flower position Monohybrid Crosses & Mendel’s Principle of Segregation o Terms P generation = parental F1 = first filial F2 = second filial, etc Monohybrid crosses – between true-breeding pea strains that differ in a single trait Reciprocal crosses – mating done both ways Smooth female * wrinkled male & wrinkled female * smooth male Convention writes female first in crosses of plants If results are same, trait is not sex-dependant Principle of uniformity in F1: all offspring of monohybrid cross of true-breeding parents are alike Ex: smooth * wrinkled all smooth Homozygous vs heterozygous o After produce F1, Mendel allowed F1 to self-fertilize non-uniform F2 (smooth + wrinkled seeds in F2): concluded that -- alternative traits in cross (smoothness or wrinkledness) were determined by particulate factors (aka genes, now) since trait disappeared and then reappeared since there were two types of traits, each factor existed in alternative forms (aka alleles, now; smooth vs. wrinkled allele) conventions: dominant trait always written firs, but base letter assignment on recessive phenotype) b/c F2 had both traits and F1 had only one, each F1 individual must have had both factors
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each child had 2 factors, one from each parent
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