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Unformatted text preview: EXAM 3 Gene Discrete unite of hereditary information consisting of specific sequence of DNA Often codes for polypeptide chain Gene Locus A particular position along a specific chromosome where a given gene is located. Allele Alternative form of a gene E.g., A,a Genetics Problems Posted on moodle A guide to the kinds of problems that will be on exam. Homozygous Having 2 identical alleles for a trait AA aa I A I A Heterozygous Having two different genes (alleles) for a trait. Aa I A I B FIGURE 14.4 Genotype The genetic makeup of an individual PP or Pp Phenotype The physical manifestation of a trait How it appears Determines by the genotype Dominant Allele Allele that is fully expressed in phenotype or a heterozygote Only a single copy is required to express the trait Represented Recessive allele In heterozygouse individual the allele that is completely masked (not expressed) in the phenotype Represented by a lowercase letter, a CLICKER QUESTIONS :Recessive alleles are not expressed bc they code for an inactive or defective enzyme? TRUE Why is recessive allele is not expressed? Bc it is inactive or defective enzyme. Generations P Parental F1 Filial one-offspring of the parental generation hybrids F2 Filial 2- offspring cross between f1 (hybrid) individuals Mendels first law The two members of gene pair segregate (separate) from each other into the gametes. CLICKER QUESTION: when does mendelian segregation occur? Anaphase 1 of meiosis. March 19, 2010 Friday, March 19, 2010 Test Cross (Fig. 14.7) How do you determine whether an individual is homozygous dominant or heterozygous? Phenotype is A (dominant) Genotype is A- (other dominant) Could be AA or Aa Cross unknown individual with a homozygous recessive individual Test Cross Outcomes Unknown ( homozygous dominant ): all offspring display the dominant trait Unknown ( heterozygous ): half the offspring display the dominant trait; half the offspring display the recessive trait Configure a Punnett Square for a test cross Figure 14.7 If the unknown is homozygous dominant All offspring from the test cross have the dominant phenotype Half the offspring will display the recessive phenotype Clicker Question: In a testcross, what is the phenotype of the unknown individual? Answer: Dominant Clicker Question: in a testcross, if the unknown is heterozygous, the offspring phenotypes will be. Answer: Half dominant, half recessive Clicker Question: In a testcross, if the unknown is homozygous, the offspring phenotypes will be Answer: All dominant Figure 14.7 A testcross Incomplete Dominance Heterozygous individuals are intermediate between the dominant and the recessive traits Three phenotypes which can relate directly to the genotypes Incomplete dominance in carnations Pictures On Moodle...
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