BIOL239 Study Guide - Final Guide: Dna Polymerase Iii Holoenzyme, Ribosome-Binding Site, Allele Frequency
12 Apr 2013
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Phenotype: observable characteristic (largely determined by genotype). Monohybrid cross: matings between individuals that only differ in one trait. Allele: alternative form of a single gene. Polymorphic: more than one wildtype allele; allele frequency greater than 1% Monomorphic: only one wildtype allele; only one allele above 1% frequency. The two alleles for each trait separate (segregate) during gamete formation then unite at random, one from each parent, at fertilization. At the dna level, alleles vary in nucleotide sequence. This can result in: new amino acid sequence, change in the amount of protein, e. g. Garden peas r allele gives the pea a round shape because this version of the starch branching enzyme is normal. The r allele has a different amino acid sequence and the enzyme is non-functional (i. e. no branched starch). Test cross: breeding an unknown genotype with a homozygous recessive will reveal its genotype. If it was homozygous dominant, all progeny are heterozygous and have the same phenotype.
