19Later research demonstrated that many proteins are composed of several polypeptides, each of which has its own gene.Therefore, Beadle and Tatum’s idea has been restated as theone gene - one polypeptide hypothesis.
81The anticodon base-pairs with a complementary codon on mRNA. If the codon on mRNA is UUU, a tRNA with an AAA anticodon and carrying phenyalanine will bind to it.Codon by codon, tRNAs deposit amino acids in the prescribed order and the ribosome joins them into a polypeptide chain.
130Practice ’90/’94In DNA replication, DNA polymerase catalyzes the reaction in whichA. The double helix unwindsB. The sugar-phosphate bonds of each strand are brokenC.A phosphate group is added to the 3’-carbon or 5’-carbon of riboseD.A nucleotide with a base complementary of the base on the template stand is added to the new DNA strandE. The two nucleotide strands come together and intertwine to form a double helix
131PracticeThe relative location of four genes on a chromosome can be mapped from the following data on crossover frequencies.GenesFrequency of crossoverB and D 5%C and A %A and B %C and B %C and D 50%Which of the following represents the relative positions of these four genes on the chromosome?A. ABCDB. ADCBC.CABDD.CBADE. DBCA
132The illustrations above represent homologous pairs of chromosomes as they appear in various stages of mitosis and meiosis (2n=2).1. At which stage do the chromosomes have the LEAST amount of DNA per cell?2. Which diagram represents anaphase of meiosis I?
133Shading indicates the presence of sickle cell anemia. The phenotype of individual C is best explained by the fact that this individual received an allele for sickle cell anemia fromA. an autosomal chromosome of each parentB. the Y chromosome contributed by the fatherC.the X chromosome contributed by the motherD.the X chromosome contributed by the fatherE. the Y chromosome contributed by the motherShading indicates the presence of sickle cell anemia.
134What is the probability that the next child of parents A and B would have had sickle cell anemia?
135The most reasonable explanation for the fact that the offspring of C and D do not have sickle cell anemia is that each received aA. sickle allele from the motherB. normal allele from the fatherC.sickle allele from each parentD.normal allele from each parentE. pair of normal alleles from the father
136Which of the following statements is correct about the four offspring of C an D? A.Only the females are carriers of the sickle cell trait.B.Only the males are carriers of the sickle cell trait.C.Only the females are heterozygous for the sickle cell trait.D.All are homozygous for the sickle cell trait.E.All are carriers of the sickle cell trait.
137Achondroplastic dwarfism is a dominant genetic trait that causes severe malformation of the skeleton. Homozygotes for this condition are spontaneously aborted (hence, the homozygous condition is lethal) but heterozygotes will develop to be dwarfed.Matthew has a family history of the condition, although he does not express the trait. Jane is an achondroplastic dwarf. Matthew and Jane are planning a family of several children and want to know the chances of producing a child with achondroplastic dwarfism.
138The genotypes of Matthew and Jane are best represented as Matthew Jane(A) AA Aa(B) Aa aa(C) aa aa(D) aa Aa(E) Aa Aa
139The probability that Matthew and Jane’s first child will be an achondroplastic dwarf is
140If three children are born to Matthew and Jane, what are the chances that the first two children will not express the trait but that the third child will be an achondroplastic dwarf?(A) 5/8(B) 4/8(C) 3/8(D) 1/8(E) 1/16