MIDTERM EXAM 2 Robichaux Section 26 February 2009 YOUR NAME Last name First name YOUR UA NetID YOU MUST CHOOSE THE SINGLE BEST ANSWER FOR EACH QUESTION YOU MUST USE A NUMBER 2 PENCIL strands 1 Of the four nitrogenous bases in DNA which of the following is a pyrimidine 2 As discussed in lecture the two polynucleotide strands of the DNA double helix a guanine b cytosine c adenine d a and c but not b e none of the above a are parallel in orientation b are held together by hydrogen bonding between purines and pyrimidines on the opposite c include sugar phosphate backbones that coil around the outside of the double helix d all of the above e b and c but not a a nucleotides are added to the end at which each growing strand has a free phosphate group b nucleotides are added to the end at which each growing strand has a free hydroxyl group on c neither of the above a both the leading strand and the lagging strand are synthesized in the 3 to 5 direction b the leading strand is synthesized in the 5 to 3 direction whereas the lagging strand is on the 5 carbon of the terminal deoxyribose sugar the 3 carbon of the terminal deoxyribose sugar 4 As the template DNA unwinds during replication 3 During DNA replication synthesized in the 3 to 5 direction thereby matching the orientation of the two template strands 5 As discussed in lecture which of the following ensures that DNA replication occurs c neither of the above with very high accuracy a proofreading by DNA polymerase b mismatch repair proteins c both of the above d none of the above a the sugar molecule in DNA is ribose b the nitrogenous base thymine occurs in RNA in place of uracil c RNA consists of a single polynucleotide strand d all of the above e none of the above 6 DNA differs from RNA in that 1 7 With respect to transcription 8 With respect to the genetic code RNA polymerase binds a the RNA transcript is antiparallel to the DNA template strand b new nucleotides are added to the 3 end of the growing RNA strand c initiation of transcription requires a promoter which is a special sequence of DNA to which d all of the above e b and c but not a a the genetic code is nearly universal b the genetic code is redundant yet unambiguous c for each codon specifying an amino acid the codon sequence is antiparallel to the d all of the above e a and b but not c corresponding nucleotide sequence in the DNA template strand Questions 9 11 refer to the following prokaryotic mRNA sequence reading from left to right in the 5 to 3 direction AUGGCUGCACAGAUAUGA 9 The corresponding sequence for the DNA template strand reading from left to right in 10 For the fourth codon in the mRNA sequence the corresponding anticodon is the 3 to 5 direction is a GCAATCATGTGAGCGCAG b TACCGACGTGTCTATACT c CGTTAGTACACTCGCGTC d none of the above a GUC b UGA c ACU d none of the above a methionine alanine aspartic acid histidine arginine b methionine lysine alanine serine tyrosine c methionine valine serine alanine alanine d none of the above 11 The mRNA sequence encodes the polypeptide sequence 12 For the prokaryotic polypeptide sequence histidine lysine glutamine phenylalanine 13 Based on the discussion in lecture about eukaryotic genes and mRNA processing which of the following CANNOT be the corresponding sequence for the DNA template strand reading from left to right in the 3 to 5 direction a GTATTCGTCAAA b GTGTTTGTCAAG c GTATTTGTCAAA d GTTTTCGTTAAA a a spliceosome excises and releases the transcribed intron sequences and joins the b protein coding genes of eukaryotes contain introns and exons c the pre mRNA contains the transcribed exons but not the transcribed introns d all of the above e a and b but not c transcribed exon sequences together to produce the mature mRNA 2 14 Based on the discussion in lecture spontaneous point mutations may arise during DNA replication because a the four bases are somewhat unstable b bases may change because of a chemical reaction such as deamination c DNA polymerase may insert the wrong base d all of the above e a and c but not b 15 During DNA replication the sequence of a DNA template strand is TACGAGGCT and the sequence of the corresponding growing leading strand is ATGCCCCGA The growing strand shows evidence of a a transition b a transversion c neither of the above 16 During DNA replication the sequence of a DNA template strand is AGGGTCACG and the sequence of the corresponding growing leading strand is TCCCATTGG The growing strand shows evidence of a a transversion b a transition c neither of the above two species of bacteria you discover a point mutation such that the sequence is GCATAGCCGTAA in one species but GCATATCCGTAA in the other species reading from left to right in the 3 to 5 direction The point mutation is a a synonymous mutation b a nonsynonymous mutation c neither of the above 18 In a polypeptide coding region of another gene you discover a point mutation such that the DNA sequence is GTGTCTGACATG in one bacterial species but GTGTCTAACATG in the other species reading from left to right in the 3 to 5 direction The point mutation is a a synonymous mutation b a nonsynonymous mutation c neither of the above 17 In comparing the template DNA sequences in a polypeptide coding region of a gene in Questions 19 23 pertain to the Neutral Theory of Molecular Evolution as developed by Motoo Kimura 19 As discussed in lecture the Neutral Theory posits that a at the level of DNA sequences genetic drift dominates evolution b negative selection on deleterious base substitutions is very important in terms of c the vast majority of base substitutions that become fixed in populations are non neutral with accounting for differences in DNA sequences respect to fitness such that selection rather than genetic drift dominates evolution at the level of DNA sequences 20 As discussed in lecture for a population of a sexually reproducing diploid organism d b and c but not a e none of the above with population size N the number of new neutral mutations that arises each generation equals a 1 2 b 2N c 1 2N d none of the above 3 22 If Ka Ks 1 the inference is that the 21 As discussed in lecture for a population of a sexually reproducing diploid organism with population size N the probability that a mutation will become fixed by genetic drift acting alone for a newly arisen and very rare allele is a 1 2N b 2N c 1 N d none of the above a nonsynonymous substitutions are advantageous and thus subject to positive selection b nonsynonymous substitutions are