GENETICS EXAM REVIEWED QUESTIONS AND 100% CORRECT COMPLETE SOLUTIONS

Why do scientists think that all forms of life on earth have a common origin? All living organisms use the same genetic code Related genes from different organisms have similar nucleotide sequences Different organisms have related genes with similar functions Related genes from different organisms have similar amino acid sequences All the choices are correct All the choices are correct If an Ss x Ss mating is performed and the progeny have the following phenotypic ratios of 3 S_ , (- indicates that the other allele is unknown) and 1 ss, it would indicate that Cannot determine the relationship between the alleles based on the information given Neither allele is dominant The S allele is dominant to the s allele The s allele is dominant to the S allele The S allele is dominant to the s allele In a dihybrid cross AAbb x aaBB, what proportion of the F2 offspring is expected to be homozygotic for at least one gene (i.e. not heterozygous for both genes)? 3/4 0 1/2 1 1/4 3/4 If the parents of a family already have two boys, what is the probability that the next two offspring will be girls? 1/8 1/4 1 1/2 1/3 1/4 If an individual has 10 gene pairs, how many different gametes can be formed if four of the gene pairs are homozygous and the remaining six gene pairs are heterozygous? 32 12 10 64 16 64 In corn, liguleless (l) is recessive to ligules (L) and green leaves (G) is dominant to non-green leaves (g). If a true-breeding (pure-breeding) plant that is liguleless and has green leaves is crossed to another true-breeding plant that has ligules and non-green leaves in the parental (P) generation, predict the proportion of F2 progeny with the genotype LlGg. Cannot be determined 1/4 1/16 1/8 1/2 1/4 The set of alleles present in an individual makes up its phenotype zygote recessive alleles genotype dominant alleles genotype The mutations found in the CF gene that result in cystic fibrosis are recessive because The CF mutations that occur result in no protein being produced, and this is the only possible way for the mutations to be recessive CF mutations only result in a protein that has normal function if there is also a normal CF allele in the cells of a carrier Normal or nearly normal cellular function can occur from the protein produced by the normal allele in a carrier CF is fatal and if the alleles that caused CF were dominant, it would not be inherited The amount of normal activity conferred by the normal CF allele is not sufficient to overcome the effect of the abnormal allele in a heterozygote Normal or nearly normal cellular function can occur from the protein produced by the normal allele in a carrier What is the best term for a cross used to determine the genotype of an individual showing a dominant phenotype? Self fertilize Testcross Reciprocal cross Monohybrid cross Cross fertilize Testcross Which ratio would indicate that a phenotype is controlled by multiple genes? 3:1 9:3:3:1 1:2:1 2:1 9:3:3:1 In rats, the allele for pigmentation (P) is dominant to the allele for albinism (p). The gene for black pigmentation (B) is dominant to the gene for cream pigmentation (b). If the dominant P allele is absent, gene B is inoperative. Predict the phenotypic ratio of the F2 progeny of a parental cross between a homozygous black rat and an albino homozygous for cream. 9 black : 3 albino : 4 cream 12 black : 3 cream : 1 albino 9 black : 3 cream : 4 albino 1 albino : 2 black : 1 cream 12 black : 3 albino : 1 cream 9 black : 3 cream : 4 albino What can explain the phenomenon where the same genotype might give rise to different phenotypes? epistasis codominance incomplete dominance pleiotropy penetrance and expressivity penetrance and expressivity Which of the following is NOT a phenotypic description of allele interactions of a single gene?