Mendelian
Genetics 

Cross Review Answers: 1. B  This problem requires the product rule to be applied in order to determine the results from two separate events. Therefore, the chances for getting heads on both coins is 1/2 * 1/2, for getting tails on both coins is 1/2 * 1/2, and for getting one head and one tail is the remaining 50%. 2. C  The only way for the recessive phenotype to be expressed is if both recessive alleles are present in the genotype. 3. D  The offspring of a cross between two hybrids should yield a 3:1 phenotypic ratio; therefore, approximately 90 offspring should be yellow. 4. A  This question is referring to a test cross; therefore, the homozygous recessive individual must be mated to the unknown. 5. C  Since the wife of the man had a father with blue eyes, she must be carrying the blueeyed allele; therefore, their children have a 50/50 chance of having blue eyes. 6. A  The product rule must be applied to solve this problem. The probability of the gametes containing an A allele is 1/2; B allele  1/1; C allele  1/1; D allele  1/1; E allele  1/1; therefore, (1/2*1*1*1*1) yields only 2 distinct kinds of gametes. 7. B  The higher the frequency of crossing over between two genes, the farther apart they are on a chromosome; therefore, the correct sequence is represented by letter B. 8. E  By definition, a dominant allele is expressed whether it is homozygous dominant or heterozygous. 9. C  Codominance exists when the heterozygote expresses both phenotypes of the homozygotes as in Sickle Cell Anemia. 10. D  Incomplete dominance exists when the heterozygote expresses a phenotype intermediate of the homozygotes as in the pink heterozygotes of the Snapdragon Flowers. 
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