Interactive Biology Multimedia Courseware From DNA To
Interactive Biology Multimedia CoursewareFrom DNA to ProteinCopyright 1998 CyberEd Inc.
From DNA to ProteinTEACHING OBJECTIVESThe following subject areas are illustrated throughout the Interactive Biology MultimediaCourseware program, From DNA to Protein. Ideally, these areas would be augmentedwith additional course work outside of this program. An Overview of DNA as the Hereditary Molecule: Including early experiments such as those performed by Sir Archibald Garrod, George Beadle, and Edward Tatum. The Physical Structure and Chemical Composition of DNA and RNA Molecules. Transcription of the DNA Molecule: Including the origin of messengerRNA(mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). Translation of the mRNA Strand: Including the roles of tRNA and rRNA,elongation of the polypeptide, and termination of translation.Copyright 1998 CyberEd Inc.2
Study Guide #1GENES AND HEREDITYWhat controls the way we look? In other words, why do you look like your parents andwhy do offspring throughout the plant and animal kingdoms tend to look like theirparents? Most of you know already that the answer lies in deoxyribonucleic acid, orDNA.Within DNA lies hereditary units known as genes.It is these genes which get passed along from generation togeneration and control an offspring's phenotype, or simply thephysical traits of an individual.How exactly do genes release their information and direct theconstruction of a new individual. It took many years tounlock the answer to this question. One of the first people toinvestigate this was the English physician Sir Archibald Garrod.Garrod suggested that genes controlled phenotype through enzymes, which regulate manyof the biochemical reactions that take place inside our bodies. He studied patientssuffering from the hereditary disease alkaptonuria, and felt that a defective gene led to thiscondition. This defective gene either resulted in no enzyme, or a faulty enzyme, beingproduced.In 1941, American scientists George Beadle and Edward Tatum produced the bestevidence that genes control the production of enzymes. Using bread mold for theirresearch, these scientists were able to conclude that one gene controls the production ofone enzyme. This is called the one gene-one enzyme hypothesis.Copyright 1998 CyberEd Inc.3
Enzymes are composed of protein. All proteins are in turn made up of amino acidsconnected into a long polypeptide chain. It is now known that one gene and Beadlecontrol the construction of each polypeptide in a protein and Tatum's hypothesis has beenchanged to the one gene-one polypeptide hypothesis.Copyright 1998 CyberEd Inc.4
Study Guide #2STRUCTURE AND COMPOSITION OF DNADNA exists as a double helix. Think of it as being like a ladder spiraling from end to end.Each side of the ladder consists of achain of sugar-phosphate groups.Each rung of the ladder consists ofone pair of nitrogenous (ornitrogen containing) bases.There are four bases found in everyDNA molecule on earth regardless of whether that moleculecomes from a human, an oak tree, or a bacterium. These four bases are:ADENINEGUANINECYTOSINETHYMINEAdenine and Guanine are both purines.Cytosine and Thymine are both pyrimidines.These bases pair only in very specific ways. Adenine always pairs with thymine. Guaninealways pairs with cytosine. A single base (adenine, guanine, cytosine, or thymine)together with a phosphate group and the sugar deoxyribose make up a nucleotide. Anucleotide is the basic unit of DNA and a single gene contains hundreds or thousands ofnucleotides.Copyright 1998 CyberEd Inc.5
Study Guide #3RNAFor a gene to control the production of a polypeptide, it must direct the linking of aminoacids. Scientist have determined that the order of the bases in three adjacent nucleotidesof a gene is the code that directs a particular amino acid be added to the growingpolypeptide chain. In other words, a three-nucleotidelong sequence codes for a specific amino acid. Each tripletof nucleotides is called a codon.Amino acids are linked into polypeptides in the cytoplasmof a cell, yet the DNA in a eukaryotic cell is confined tothe nucleus. How does DNA in the nucleus direct theproduction of polypeptides in the cytoplasm? The answeris ribonucleic acid, or RNA.There are only two differences between the chemical makeup of RNA and the chemicalmakeup of DNA. In RNA, thymine is replaced by the base uracil.In RNA, the sugar is ribose rather than the deoxyribose found in DNA.Structurally, the difference between RNA and DNA is that RNA exists as a single strandof nucleotides, whereas DNA is made up of two nucleotide strands.Copyright 1998 CyberEd Inc.6
To form a protein from the polypeptide directions encoded in DNA, two processes areinvolved: transcription and translation. Transcription occurs first and is the process bywhich the genetic code carried by DNA is copied by RNA. Translation is the process bywhich the message transcribed by RNA is converted, in the cytoplasm, into a polypeptide.Copyright 1998 CyberEd Inc.7
Study Guide #4TRANSCRIPTIONMESSENGER RNABefore RNA can make a copy of DNA, it must gain access to the code. This is done withthe aid of an enzyme called RNApolymerase. RNA polymerasebinds to DNA and "unzips" it that is it separates the two strandsof DNA. A single, unpairedstrand of DNA now serves as thetemplate for RNA.Next, free RNA nucleotides ssemble along the exposed DNA strand and line up with theircomplimentary bases. For instance, an RNA adenine will line up with each exposed DNAthymine. Remember though, there is no thymine in RNA. Therefore, an RNA uracil willline up with each exposed DNA adenine.This pairing of RNA with their complementary DNA bases continues until a certain"STOP" code is reached on theDNA strand. At this point, theRNA strand stops elongating.The newly formed RNA strandthen breaks away, the RNApolymerase breaks free, and thetwo DNA strands reconnect.The RNA molecule that was copied from the DNA strand now carries the information toproduce a polypeptide and is called messenger RNA, or mRNA. It is called this because itserves as a genetic messenger between DNA and the protein-making machinery in thecytoplasm.Copyright 1998 CyberEd Inc.8
Each triplet of nucleotides in the mRNA makes up a codon. Each codon codes for aspecific amino acid in thepolypeptide chain.In eukaryotic organisms, such ashumans, mRNA undergoes a fewalterations in the nucleus beforemoving into the cytoplasm. Ineukaryotes, the protein-codingsegments of genes do not lie next to each other. Instead, they are separated by nonprotein coding segment called introns. The portions that actually code for proteins(polypeptides) are called exons.The first step in the processing of mRNA in the nucleus is the placement of a cap and tailon the mRNA strand. The tail iscalled a poly-a tail because itconsists of about 200 adeninenucleotides. Together, the capand tail prevent the mRNAstrand from being broken downby enzymes in the cytoplasm.After the cap and tail are inplace, the introns are cut out and the exons are spliced together. In this form, the mRNAmoves into the cytoplasm where the process of translation takes place.Copyright 1998 CyberEd Inc.9
Copyright 1998 CyberEd Inc.10
Study Guide #5TRANSCRIPTIONTRANSFER RNA AND RIBOSOMAL RNAIn the previous study guide, you learnedof messenger RNA, or, mRNA. Asecond type of RNA is transfer RNA, or,tRNA.Like mRNA, tRNA is transcribed fromDNA in the nucleus of the cell. tRNA istypically much smaller than is mRNA.Whereas mRNA may be severalthousand nucleotides in length, tRNAhas only about 80 nucleotides.At one end of the tRNA molecule, there is a short tail. This tail serves as the amino acidattachment site. At another position on the tRNA molecule, there is a loop of nucleotides.Within this loop lies a sequence of 3 bases which make up an anticodon.An anticodon is the complementof an mRNA codon. In otherwords, the anticodon of tRNAwill match up with the codon onmRNA. Therefore, if you seetRNA with the sequence uracil,adenine, cytosine (UAC) youknow it must match up with an mRNA sequence of adenine, uracil, guanine (AUG).Copyright 1998 CyberEd Inc.11
.tRNA e.mRNA codon.Each mRNA codon calls for aspecific amino acid. Thisamino acid will be carried by a tRNA molecule. In other words, the anticodon that bindsto its codon will be found on a tRNA molecule that always carries a specific amino acid.Each specific tRNA carries a specific amino acid. Thus, tRNA acts as a vehicle forbringing up the correct amino acid at the correct time.The third type of RNA is ribosomal RNA, or rRNA. Like the other two types, rRNA istranscribed from DNA.Within the nucleus of a cellis a structure known as anucleolus. Inside of thenucleolus, rRNA is joinedwith various proteins toform ribosomes. Eachribosome consists of twosubunits of unequal size (a large and a small subunit). The ribosome is the site of proteinsynthesis.After the RNA and ribosomes have been formed, they pass from the nucleus tothe cytoplasm via pores in the nuclear envelope, which is the membrane that surrounds thenucleus. Within the cytoplasm are all the amino acids needed for the next stage,translation.Copyright 1998 CyberEd Inc.12
Study Guide #6TRANSLATIONWhereas transcription takes place inside the nucleus, translation occurs outside of thenucleus in the cytoplasm.During translation, theinformation held within mRNAis used to form a polypeptide.Once they reach the cytoplasm,tRNA molecules becomeattached to their specific aminoacids. This creates a pool of tRNA molecules with amino acids in tow.Also in the cytoplasm, ribosomes become attached to mRNA at various sites along thestrand. The small ribosomalsubunit is the first unit of theribosome to attach to the mRNAstrand. At the same time, tRNAwith the anticodon AUC attachesto mRNA at the site of itscomplementary codon AUG.AUG is an initiator codon. Thatis, it is AUG codons at whichtranslation starts.Once tRNA has attached to mRNA at the initiator codons, the large ribosomal subunitsjoin the complex. In the large subunit are two groove-like sites known as the P site andthe A site. Into these two grooves fit the tRNA molecules carrying amino acids.When the large subunit joins the complex, it attaches so that the initiator codon is in the Psite. This leaves the A site open. Another tRNA with an anticodon corresponding to theCopyright 1998 CyberEd Inc.13
next codon in the line fills in the A site. As this new tRNA molecule fills in the A site, apeptide bond links the aminoacid in the P site with that inthe A site. This forms a twopeptide long chain, known as adipeptide.Once the dipeptide bondforms, three things happen.First, the bond linking the amino acid in the P site to the tRNA that carried it there breaks.The peptide bond remains intact though, so the dipeptide still exists. Second, the tRNA inthe P site breaks free from the mRNA strand. This leaves an open P site. Third, theribosome slides one codon down the mRNA strand. The tRNA that was filling the A sitenow fills the P site. The A site is once again free to receive a tRNA carrying an aminoacid.Molecules of amino acid carrying tRNA continue to enter and leave the ribosomal sites asthe ribosome moves along the mRNA strand. Thus, the dipeptide quickly becomes apolypeptide (many peptides).The polypeptide continues to growuntil a special stop codon on themRNA strand is reached. At thispoint, the A site accepts a proteinknown as a release factor instead ofa tRNA molecule. The releasefactor causes the last tRNA in the Psite to exit the ribosome. At theCopyright 1998 CyberEd Inc.14
same time, the bond is broken between the polypeptide and the tRNA. The polypeptide isnow free and coils itself into a functional protein. Finally, the two ribosomal subunitsdetach from the mRNA.Copyright 1998 CyberEd Inc.15
From DNA to ProteinQUIZ PACThe following quizzes are meant to test student understanding of specific topic areascovered in the Interactive Biology Multimedia Courseware program, From DNA toProtein. Many, but not all, of these questions have been addressed directly in the studyguides designed to strengthen student understanding of these topics.QUIZ #1QUIZ #2QUIZ #3QUIZ #4QUIZ #5QUIZ #6EXAMDNA and HeredityStructure & Composition of ensive ExamCopyright 1998 CyberEd Inc.16
Quiz #1DNA AND HEREDITY1. The basic unit of heredity is the gene.A. TrueB. False2. is the physical traits of an individual.A. GenotypeB. PhysiqueC. PhenotypeD. Genome3. Sir Archibald Garrod studied the hereditary disease .A. alkaptonuriaB. breast cancerC. cystic fibrosisD. down syndrome4. Garrod felt that lead to the condition he studied.A. exposure to chemicalsB. non-disjunctionC. UV radiationD. a faulty gene5. Working with bread mold, George Beadle and Edward Tatum came up with thehypothesis.A. one chemical-one mutationB. one gene-one mutationC. one mutation-one enzymeD. one gene-one enzyme6. Beadle and Tatum's hypothesis was later changed to the .A. one chemical mutation-one enzyme hypothesisB. one gene-one enzyme theoryC. one mutation-one enzyme theoryCopyright 1998 CyberEd Inc.17
D. one gene-one polypeptide hypothesis7. Enzymes area composed of , which are in turn composed of .A. genes, proteinsB. genes, amino acids linked to form polypeptidesC. amino acids, polypeptides linked to form proteinsD. proteins, amino acids linked to form polypeptidesCopyright 1998 CyberEd Inc.18
Quiz #2STRUCTURE AND COMPOSITION OF DNA1. DNA exists as a double helix.A. TrueB. False2. A nucleotide is the basic unit of DNA.A. TrueB. False3. Each "rung" in the DNA "ladder" consists of .A. a single nitrogenous baseB. a pair of nitrogenous basesC. three nitrogenous basesD. two pairs of nitrogenous bases4. Which of the following is NOT a base found in DNA?A. AdenineB. GuanineC. PhenylalanineD. All of the above ARE bases found in DNA.5. Which of the following is NOT a base found in DNA?A. UranineB. CytosineC. ThymineD. All of the above ARE bases found in DNA.6. Adenine ALWAYS pairs with what base?A. ThymineB. GuanineC. PhenylalanineD. AdenineCopyright 1998 CyberEd Inc.19
7. Cytosine ALWAYS pairs with what base?A. UranineB. GuanineC. AdenineD. Cytosine8. A nucleotide of DNA consists of .A. a phosphate groupB. a single baseC. the sugar deoxyriboseD. All of the above.Copyright 1998 CyberEd Inc.20
Quiz #3RNA1. RNA has the exact structure and composition of DNA.A. TrueB. False2. For a gene to control the production of a polypeptide, it must direct the linking of.A. polypeptidesB. proteinsC. amino acidsD. nucleotides3. adjacent nucleotides in a gene code for .A. Two, a specific polypeptideB. Two, a specific amino acidC. Three, a specific polypeptideD. Three, a specific amino acid4. This of nucleotides is known as .A. doublet, a codonB. doublet, a conduitC. triplet, a codonD. triplet, a conduit5. RNA allows DNA, which remains in the nucleus, to .A. become much less critical to the survival of the cellB. direct the production of polypeptides in the cytoplasmC. leave the nucleus for a short timeD. lay dormant for long periods of time6. A difference between the CHEMICAL makeup of RNA and DNA is .A. in RNA, the base THYMINE is replaced by the base URACILB. in RNA, the sugar DEOXYRIBOSE is replace by RIBOSEC. Both A and BD. Neither A nor BCopyright 1998 CyberEd Inc.21
7. A difference between the STRUCTURAL makeup of RNA and DNA is.A. RNA exists as a single strandB. RNA exists as a double helixC. RNA exists as a triple helixD. RNA exists as a pair of double helixesCopyright 1998 CyberEd Inc.22
Quiz #4TRANSCRIPTION1. The enzyme RNA polymerase helps break down DNA.A. TrueB. False2. serves as the template for making a strand of RNA.A. A single strand of DNAB. Two strands of DNAC. Three strands of DNAD. Two strands of RNA3. The RNA base pairs up with the DNA base GUANINE.A. thymineB. guanineC. cytosineD. uracil4. The RNA base pairs up with the DNA base ADENINE.A. adenineB. thymineC. cytosineD. uracil5. The RNA strand elongates until .A. the entire chromosome has been transcribedB. the cell runs out of RNA basesC. a specific "stop" code is reached on the DNA strandD. the DNA strand is completely degraded6. After elongation of the RNA strand is complete, and .A. the RNA becomes a part of the chromosome, the DNA completely degradesB. the RNA strand breaks free, the DNA strands reconnectC. the RNA strand breaks free, the cell dividesD. the RNA becomes a part of the chromosome, the cell dividesCopyright 1998 CyberEd Inc.23
7. The RNA strand made from transcription of DNA is .A. messenger RNAB. mobile RNAC. micro RNAD. message RNA8. Each triplet of nucleotides on mRNA make up .A. a tripodB. a genetic codeC. a codonD. an mRNA base9. In organisms, mRNA undergoes a few alterations.A. allB. eukaryoticC. prokaryotic10. After these alterations, mRNA moves .A. into the nucleusB. out of the cellC. into the chromosomeD. into the cytoplasm11. The segments of mRNA which code for proteins are known as and thenon-protein coding segments that are removed are known as .A. introns, exonsB. exons, introns12. In processing of mRNA, to help prevent the mRNA strand from beingbroken down by enzymes.A. a cap is added to the strandB. a poly-A tail is added to the strandC. Both A and B.D. Always A and sometimes B.Copyright 1998 CyberEd Inc.24
Quiz #5TRANSCRIPTION1. The type of RNA that makes a direct copy of a gene sequence is known as messengerRNA, or mRNA.A. TrueB. False2. Typically, tRNA is much larger than is mRNA.A. TrueB. False3. tRNA stands for .A. transcription RNAB. translocation RNAC. transduction RNAD. transfer RNA4. At one end of a tRNA molecule is a tail that serves as what?A. An amino acid attachment site.B. A device to prevent the tRNA from being degraded.C. A means of movement for the tRNA.5. At another point on a tRNA molecule is a sequence of threebases that make up .A. a codonB. a genetic codeC. an anticodon6. The purpose of the on tRNA is to match up with its complementaryon mRNA.A. anticodon, codonB. codon, anticodonC. codon, codonD. genetic code, genetic codeCopyright 1998 CyberEd Inc.25
7. The tRNA sequence UAC (uracil, adenine, cytosine) will match up with the sequenceon mRNA.A. ATG (adenine, thymine, guanine)B. UAC (uracil, adenine, cytosine)C. AUG (adenine, uracil, guanine)D. CAU (cytosine, adenine, uracil)8. Each sequence of three bases on an mRNA molecule codes for which isbrought to the mRNA by .A. a specific amino acid, a tRNA molecule carrying the exact amino acid neededB. a specific tRNA molecule, a specific amino acidC. a specific protein, a tRNA molecule carrying the exact protein neededD. a tail that prevents mRNA from being degraded in the cytoplasm, tRNA9. rRNA stands for .A. reverse RNAB. restricted RNAC. regulation RNAD. ribosomal RNA10. rRNA is produced .A. in the cytoplasmB. in the nucleolusC. only once during the life of the cellD. only immediately before the cell divides11. rRNA is joined with various proteins to form .A. various regulatory moleculesB. structures important in reverse transcriptionC. restricted proteins used only inside of the cellD. structures known as ribosomes, which are needed for transcription12. All three types of RNA (mRNA, tRNA, and rRNA) move after they aremanufactured.A. into the nucleusB. into the nucleolusC. outside of the cellD. into the cytoplasmCopyright 1998 CyberEd Inc.26
Quiz #6TRANSLATION1. Translation occurs inside of the nucleus.A. TrueB. False2. Translation is the mechanism by which information held within mRNA is used to forma polypeptide.A. TrueB. False3. Once reaching the cytoplasm, tRNA molecules become attached to .A.B.C.D.each othersingle strands of DNAtheir specific amino acidsNone of the above.4. The ribosomal subunit is the first unit of the ribosome to attach to themRNA strand.A.B.C.D.topbottomsmalllarge5. In translation, the sequence serves as an initiator codon all along the mRNAstrand.A. AUCB. GCGC. UAG6. The first anticodon that attaches to the mRNA strand is what?A. AUCB. CGCC. UAGCopyright 1998 CyberEd Inc.27
7. The second ribosomal subunit that attaches and completes the complex is theribosomal subunit.A.B.C.D.topbottomsmalllarge8. The two groove-like sites in the ribosomal complex into which tRNA molecules fit are.A.B.C.D.the GCG and the CGC sitethe front and the back sitethe A and the P sitethe A and the B site9. As the ribosomes slide along the mRNA strand, link the amino acidstogether.A.B.C.D.peptide bondshydrogen bondsdouble bondspolypeptide bonds.10. What is formed after the first bond in question #9 is made?A.B.C.D.A dipeptideA dihydro amino aciddouble stranded amino acidNone of the above.11. As the ribosomes slide along the mRNA strand, tRNA molecules exit theand enter the .A.B.C.D.cytoplasm, nucleusinactive stage, active stageP site, A siteA site, P siteCopyright 1998 CyberEd Inc.28
12. As the ribosomes slide along the mRNA strand, is formed.A.B.C.D.E.DNARNAa polyhydro amino acida double stranded amino acid chainsa polypeptide13. The structure in question #12 continues to elongate until .A.B.C.D.E.the cell exhausts its supply of tRNAthe ribosomes reach a special stop codonthe ribosomes accept a release factor proteinAll of the above.B and C only.14. The end product of translation is .A. single stranded DNAB. double stranded DNAC. single stranded RNAD. a functional proteinCopyright 1998 CyberEd Inc.29
From DNA to ProteinCOMPREHENSIVE EXAMThe following exam is based on the Interactive Biology Multimedia Courseware program,From DNA to Protein. Most, but not all, of these questions have been addressed directlyin the study guides. All of the questions on this exam, however, are based on informationput forthin the program.Please determine if the following statements are true or false.1. The basic unit of heredity is the chromosome.A. TrueB. False2. A genotype consists of all the physical characteristics that an organism possesses.A. TrueB. False3. DNA exists as a double helix.A. TrueB. False4. DNA and RNA have identical structure and composition.A. TrueB. False5. The enzyme RNA polymerase "unzips" DNA molecules.A. TrueB. False6. For a gene to control the production of a polypeptide, it must direct the linking ofamino acids.A. TrueB. FalseCopyright 1998 CyberEd Inc.30
7. The type of RNA that makes a direct copy of a gene sequence is known as messengerRNA, or mRNA.A. TrueB. False8. Typically, tRNA is much larger than mRNA.A. TrueB. False9. Translation occurs in the cytoplasm.A. TrueB. FalseIn the following portion of the exam, please choose the letter beside the word, words, orphrase that best completes each sentence.10. Sir Archibald Garrod studied the hereditary disease .A.B.C.D.alkaptonuriabreast cancercystic fibrosisDown syndrome11. George Beadle and Edward Tatum came up the hypothesis.A.B.C.D.one chemical - one mutationone gene - one mutationone mutation - one enzymeone gene - one enzyme12. Their hypothesis was later changed to the .A.B.C.D.one chemical mutation - one enzyme hypothesisone gene - one enzyme theoryone mutation - one enzyme theoryone gene - one polypeptide hypothesisCopyright 1998 CyberEd Inc.31
13. Enzymes are composed of , which are in turn composed of .A.B.C.D.genes, proteinsgenes, amino acids linked to form polypeptidesamino acids, polypeptides linked to form proteinsproteins, amino acids linked to form polypeptides14. Each "rung" in the DNA "ladder" consists of .A.B.C.D.a single nitrogenous basea pair of nitrogenous basesthree nitrogenous basestwo pairs of nitrogenous bases15. Which of the following is NOT a base found in DNA?A.B.C.D.AdenineGuaninePhenylalanineAll of the above ARE bases found in DNA.16. Cytosine ALWAYS pairs with what . A nucleotide of DNA consists of .A.B.C.D.a phosphate groupa single basethe sugar deoxyriboseAll of the above make up a nucleotide.18. adjacent nucleotides in a gene code for .A.B.C.D.Two, a specific polypeptideTwo, a specific amino acidThree, a specific polypeptideThree, a specific amino acidCopyright 1998 CyberEd Inc.32
19. A of nucleotides is known as .A.B.C.D.pair, a genetriplet, a codonchain, an enzymepolypeptide, a protein20. RNA allows DNA, which remains in the nucleus, to .A.B.C.D.become much less critical to cellular survivaldirect the production of polypeptides in the cytoplasmleave the nucleus for a short timelay dormant for long periods of time21. A difference between the CHEMICAL makeup of RNA and DNA is .A.B.C.D.in RNA, the base THYMINE is replaced by the base URACILIn RNA, the sugar DEOXYRIBOSE is replaced by RIBOSEBoth A and B.Neither A nor B.22. A difference between the STRUCTURAL makeup of RNA and DNA is .A.B.C.D.RNA exists as a single strandRNA exists as a double helixRNA exists as a triple helixRNA exists as a pair of helixes23. The RNA base pairs up with the DNA base ADENINE.A.B.C.D.THYMINEGUANINECYTOSINEURACIL24. The RNA strand elongates until .A.B.C.D.the entire chromosome has been transcribedthe cell runs out of RNA basesa specific "stop" code is reached on the DNA strandthe DNA strand is completely degradedCopyright 1998 CyberEd Inc.33
25. After elongation of the RNA strand is complete, and .A.B.C.D.the RNA becomes a part of the chromosome, the DNA completely degradesthe RNA strand breaks free, the DNA strands reconnectthe RNA strand breaks free, the cell dividesthe RNA becomes a part of the chromosome, the cell divides26. In organisms, mRNA undergoes a few alterations.A. allB. eukaryoticC. prokaryotic27. The segments of mRNA which code for proteins are known as and thenon-protein coding segments that are removed are known as .A. introns, exonsB. exons, introns28. In processing mRNA, to help prevent the mRNA strand from being brokendown by enzymes.A.B.C.D.a cap is added to the stranda poly-A tail is added to the strandBoth A and B.Always A and sometimes B.29. At one end of a tRNA molecule is a tail that serves as what?A. An amino acid attachment site.B. A means of attaching tRNA to DNA.C. A means of movement for the tRNA, like a tadpole's tail.30. At another point on a tRNA molecule is a sequence of three bases that make up.A. a genetic codeB. a codonC. an anticodonCopyright 1998 CyberEd Inc.34
31. The purpose of the on tRNA is to match up with its complementaryon mRNA.A.B.C.D.anticodon, codoncodon, anticodoncodon, codongenetic code, genetic code32. Each sequence of three bases on an mRNA molecule codes for which isbrought to the mRNA by .A.B.C.D.a specific amino acid, a tRNA molecule carrying the exact amino acid neededa specific tRNA molecule, a specific amino acida specific protein, a tRNA molecule carrying the exact protein neededa tail that prevents mRNA degradation, tRNA33. rRNA is joined with various proteins to form .A.B.C.D.various regulatory moleculesstructures important in reverse transcriptionrestricted proteins used only inside of the cellstructures known as ribosomes, which are needed for transcription34. is the mechanism by which information held in mRNA is used tomanufacture a e transcriptionReverse translation35. Once reaching the cytoplasm, tRNA molecules become attached to .A.B.C.D.each otherDNA strandsspecific amino acidsspecific polypeptidesCopyright 1998 CyberEd Inc.35
36. The ribosomal subunit is the first subunit to attach to the mRNA strand,followed by the .A.B.C.D.small, large ribosomal subunitlarge, small ribosomal subunittop, bottom ribosomal subunitbottom, top ribosomal subunit37. As ribosomes slide along the mRNA strand, bonds link together.A.B.C.D.hydrogen, amino acidspeptide, tRNA moleculeshydrogen, tRNA moleculespeptide, amino acids38. Ribosomes continue to slide along the mRNA strand until .A.B.C.D.reaching a stop codonreaching the end of the mRNA strandall the tRNA molecules have been used upreaching a stop anticodonIn the following portion of the exam, please fill in the word or phrase that best completeseach sentence.39. are the basic units of DNA.40. The DNA bases and are both purines.41. The RNA base pairs with the DNA base ADENINE.42. The RNA strand made from the transcription of DNA is .Copyright 1998 CyberEd Inc.36
43. The "t" in tRNA stands for .44. On mRNA, the sequence UAG serves as .45. The final substance accepted by a ribosome prior to the polypeptide breaking free is aprotein known as a .Copyright 1998 CyberEd Inc.37
From DNA to ProteinANSWER GUIDEQUIZ PACQUIZ #11. A2. C3. A4. D5. D6. D7. D8. DQUIZ #21. A2. A3. B4. C5. A6. A7. BQUIZ #31. B2. C3. D4. C5. B6. C7. A8. C9. B10. D11. B12. CQUIZ #41. B2. A3. C4. D5. C6. B7. A8. A9. D10. B11. D12. DQUIZ #51. A2. B3. D4. A5. C6. A7. C8. C9. A10. A11. C12. E13. E14. DQUIZ #61. B2. A3. C4. C5. C6. A7. DCOMPREHENSIVE EXAM1.2.3.4.5.6.7.8.BBABAAAB9. A10. A11. D12. D13. D14. B15. C16. B17.18.19.20.21.22.23.24.Copyright 1998 CyberEd 35.36.37.38.39.40.D41. uracilB42. messenger RNA (or mRNA)C43. transcriptionA44. an initiator codonD45. release
makeup of DNA. In RNA, thymine is replaced by the base uracil. In RNA, the sugar is ribose rather than the deoxyribose found in DNA. Structurally, the difference between RNA and DNA is that RNA exists as a single strand of nucleotides, whereas DNA is made up of two nucleotide strands.
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