NOTE: QUESTIONS 1-5 ARE ON MATERIAL THAT WILL NOT BE COVERED ON YOUR EXAM BIOL . 303 EXAM II 10/20/05 Name________________________ 1. It is usually easier to identify spontaneous mutations in bacteria than most eukaryotes because 1. mutations are visible as color changes within a bacterial plaque. 2. mutations can be induced via exposure to the bacteriophage T1. 3. given the haploid condition of most bacteria, mutations are phenotypically expressed readily in bacterial cells. 4. mutations occur at a much higher frequency in bacteria. 2. In conjugation, genetic information is transferred 1. from one cell into the culture medium, where it is taken up by another cell. 2. with the help of a viral go-between. 3. in a bidirectional fashion between two cells. 4. from one bacterium to another. 3. Hfr bacterial cells exhibit the highest levels of gene transfer because 1. they contain two distinct F factors. 2. they induce the production of significantly more sex pili than normal F+ cells. 3. rather than existing as an isolated plasmid, the F factor is incorporated within the main chromosome where it can transfer many genes at one time. 4. they do not require conjugation for gene transfer. 4. In cotransformation 1. non-linked genes are passed simultaneously from one cell to another. 2. a bacterial cell receives two adjacent genes on a single piece of DNA from the medium. 3. two bacterial cells within a culture are transformed by the same genetic material. 4. it is not uncommon for the entire bacterial chromosome and F factor to be passed from one cell to another. 5. The name for the general category of DNA molecules into which double-stranded circular extrachromosomal DNA elements such as F factors would fall is 1. capsid 2. plasmid 3. plaque 4. partial diploid 6. In humans, the genetic basis for determining the sex “male” is accomplished by the presence of 1. the Y chromosome 2. one X chromosome 3. a balance between the number of X chromosomes and the number of haploid sets of autosomes 4. multiple alleles scattered throughout the autosomes 7. Klinefelter syndrome in humans, which leads to underdeveloped testes and sterility, is caused by which chromosomal condition? 1. 2. 3. 4. 47, XXY 47, 21+ 45, X 47, XYY 8. In birds, sex is determined by a ZW chromosome scheme, which is much like the typical XY scheme seen in humans and many other organisms. However, in birds the system is reversed. Males are ZZ (similar to XX in humans) and females are ZW (similar to XY in humans). A lethal recessive allele that causes death of the embryo occurs on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female? 1. 1:1 male to female 2. 3:1 male to female 3. 1:2 male to female 4. 2:1 male to female 9. Hemophilia is caused by several genetic factors; one, a sex-linked recessive gene, is the subject of this problem. Assume that a man with hemophilia marries a normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia? (Note: in this problem you must include the probability of having a daughter in your computation of the final probability.) 1. 1/16 2. 1/8 3. 1/4 4. 1/2 10. What is the expected number of Barr bodies in an individual with the karyotype XXYYY? 1. 0 2. 1 3. 2 4. 3 11. When an organism gains or loses one or more chromosomes but not a complete haploid set, the condition is known as 1. polyploidy 2. aneuploidy 3. triploidy 4. trisomy 12. The condition known as cri-du-chat syndrome in humans has a genetic constitution designated as. 1. 45, X 2. 46,5p3. triploidy 4. trisomy 13. A genomic condition that may be responsible for some forms of fragile-X syndrome, as well as Huntington disease, involves 1. F plasmids inserted into the FMR-1 gene. 2. expansion of trinucleotide repeats. 3. multiple inversions in the X chromosome. 4. single translocations in the X chromosome. 14. Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement of 46 chromosomes plus one (extra) chromosome #21. Such individuals therefore have 47 chromosomes. While there is impaired fertility of both sexes, females are more likely to be fertile than males. Assume that children are born to a female with Down syndrome and a normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome? 1. One half of the offspring will be expected to have Down syndrome. 2. None of the offspring would be expected to have Down syndrome. 3. All the children would be expected to have Down syndrome. 4. Two-thirds of the offspring would be expected to have Down syndrome. 15. While the most frequent forms of Down syndrome are caused by a random nondisjunction of chromosome #21, Down syndrome occasionally runs in families with apparently normal individuals having children with Down syndrome. The cause of this form of familial Down syndrome is 1. 2. 3. 4. 16. an inversion involving chromosome #21 too many X chromosomes a translocation between chromosome #21 and another chromosome a maternal age effect Nondisjunction 1. can lead to aneuploidy. 2. does not alter a karyotype. 3. turns a diploid genome into a haploid genome. 4. is responsible for familial Down syndrome. 17. The observation that a fly heterozygous for the double Bar allele and the wildtype allele (genotype = BD/B+) has a different phenotype than a fly that is homozygous for the Bar eye allele (genotype = B/B) serves as an example of the phenomenon known as 1. chaos. 2. inversions. 3. incomplete penetrance. 4. position effect. 18. The genetic material of most living things is 1. deoxyribonucleic acid. 2. ribonucleic acid. 3. RNA. 4. polysaccharide. 19. In the classic experiment conducted by Hershey and Chase, why were the bacteria radioactive after they had been infected with viruses which had been grown on medium containing 32P? 1. The bacteria had incorporated radioactive proteins into their cell membranes. 2. The radioactive viruses (coats plus DNA) were injected into the bacteria. 3. The bacteria contained radioactive viral DNA 4. None of the above. 20. The basic structure of a nucleotide includes the following components: 1. amino acids. 2. base, sugar, phosphate. 3. phosphorous and sulfate. 4. all of the above. 21. If 15% of the nitrogenous bases in a sample of DNA from a particular organism is thymine, what percentage should be cytosine? 1. 15% 2. 30% 3. 70% 4. 35% 22. Is the molecule to the right DNA or RNA, and is the arrow closest to the 5' or 3' end? 1. DNA, 3’ end 2. RNA, 3’ end 3. DNA, 5’ end 4. RNA, 5’ end A T Refer to the following figures for question 23 a d. 23. b. c. e. Which diagram shows a nucleotide with a purine base? 1. Figure a 2. Figure b 3. Figure c 4. Figure d 24. In E. coli bacteria, which terms accurately reflect the nature of replication of the genome? 1. bidirectional and fixed point of initiation. 2. unidirectional and conservative. 3. unidirectional and fixed point of initiation. 4. multirepliconic. 25. In the Meselson-Stahl experiment, what was the density distribution of the isolated DNA molecules two generations after shifting bacteria from "heavy" to "light" growth medium? 1. 100% of the molecules were of heavy density. 2. 50% were of heavy density, 50% were intermediate density. 3. 100% were of intermediate density. 4. 50% were of light density, 50% were intermediate density. For questions 26-27 refer to the replication fork depicted below: 5’ 3’ B A 3’ 5’ B B C 5’ 3’ 26. Item A is called 1. 2. 3. 4. 27. the leading strand. primase. single strand binding protein. an Okazaki fragment. B is most likely: 1. an RNA primer. 2. a DNA primer. 3. DNA polymerase III. 4. an exonuclease. 28. The enzyme called “telomerase” 1. contains a reverse transcriptase. 2. contains a molecule of RNA. 3. helps regulate the cell cycle. 4. all of the above. 29. The enzyme that appears to be inappropriately expressed in cancer cells and helps to maintain the very ends of eukaryotic chromosomes is called 1. topoisomerase. 2. ligase. 3. telomerase. 4. terminase. 30. In addition to highly repetitive and unique DNA sequences, a third category of DNA sequences exists. What is it called and what types of elements are involved? 1. 2. 3. 4. composite DNA, telomeres and heterochromatin dominant DNA, euchromatin and heterochromatin multiple gene family DNA, hemoglobin and 5.0S RNA moderately repetitive DNA, SINEs, LINEs, and VNTRs 31. Chromatin of eukaryotes is organized into repeating interactions with protein octomers called nucleosomes. Nucleosomes are composed of which class of molecules? 1. 2. 3. 4. 32. histones glycoproteins lipids nonhistone chromosomal proteins In eukaryotic chromatin, the next highest level of organization above "beads-ona-string" is 1. the 30 nm fiber. 2. chromatin loops. 3. the nuclear matrix. 4. the metaphase chromosome. 33. Most DNA occurring in nature 1. 2. 3. 4. is relaxed. is supercoiled. is “naked” and is not complexed with proteins has ends that are free to rotate. 34. Mutations which arise in nature from no particular artificial agent are called 1. induced mutations. 2. spontaneous mutations. 3. chromosomal aberrations. 4. cosmic mutations. 35. Two terms used to describe categories of mutational nucleotide substitutions in DNA are called 1. base analogues and frameshift. 2. error prone and spontaneous. 3. transversions and transitions. 4. euchromatic and heterochromatic. 36. A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be which of the following? 1. base analogue. 2. transversion. 3. transition. 4. frameshift. 37. Ultraviolet light causes pyrimidine dimers to form in DNA. Some individuals are genetically incapable of repairing some dimers at "normal" rates. Such individuals are likely to suffer from 1. xeroderma pigmentosum. 2. phenylketonuria. 3. muscular dystrophy. 4. Huntington disease. 38. In mammals, DNA double-strand breaks may be repaired by 1. mismatch repair. 2. base excision repair. 3. nucleotide excision repair. 4. nonhomologous end-joining 39. In the first step of base excision repair 1. 2. 3. 4. 40. a phosphodiester bond is broken two nicks are made surrounding the DNA damage a break in DNA is sealed by DNA ligase a base is removed by the action of a DNA glycosylase The simplest type of transposable elements in bacteria are known as 1. transposons. 2. insertion sequences. 3. Ds elements. 4. Ty elements. BELOW ARE SOME ADDITIONAL QUESTIONS ON MATERIAL THAT WILL BE COVERED ON YOUR EXAM 1. When scientists were attempting to determine the features of the genetic code, Crick and co-workers found that when three base additions or three base deletions occurred in a single gene, the wild type phenotype was sometimes restored. This observation supported the hypothesis that 1. 2. 3. 4. the code is triplet. AUG is the initiating triplet. the code is overlapping. there are three amino acids per base. 2. In 1964, Nirenberg and Leder used the triplet binding assay to determine specific codon assignments. A complex of which of the following components was trapped on the nitrocellulose filter? 1. 2. 3. 4. 3. ribosomes and DNA free tRNAs charged tRNA, RNA triplet, and ribosome uncharged tRNAs and ribosomes Which of the following is true? 1. every amino acid is coded for by a single codon. 2. there are more amino acids than there are codons. 3. every codon codes for an amino acid. 4. each codon in a gene codes for no more than one single amino acid. 4. The genetic code is “degenerate” because 1. there are more codons than amino acids. 2. there are more amino acids than codons. 3. different organisms use different codons to encode the same amino acid. 4. some codons specify more than one amino acid. 5. What is the name given to the three bases in a messenger RNA that bind to the anticodon of tRNA to specify an amino acid placement in a protein? 1. 2. 3. 4. protein anti-anticodon cistron codon 6. When studying the initiation of transcription, one often finds consensus sequences located in the region of the DNA where RNA polymerase(s) bind. Which are common consensus sequences? 1. 2. 3. 4. 7. CAAT, TATA GGTTC, TTAT TTTTAAAA, GGGGCCCC any trinucleotide repeat An intron is a section of 1. 2. 3. 4. protein that is clipped out posttranslationally. RNA that is removed during RNA processing. DNA that is removed during DNA processing. transfer RNA that binds to the anticodon. 8. Three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes are 1. 2. 3. 4. 5'-capping, 3'-poly(A) tail addition, splicing 3'-capping, 5'-poly(A) tail addition, splicing removal of exons, insertion of introns, capping 5'-poly(A) tail addition, insertion of introns, capping