Genetics: A Conceptual Approach, 5th Edition Solution Manual

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Chapter One: Introduction to GeneticsCOMPREHENSION QUESTIONSSection 1.1*1.How did Hopi culture contribute to the high incidence of albinism among members of theHopi tribe?Solution:In Hopi culture, albino individuals were considered special and awarded special status inthe village. Hopi male albinos were not required to work the fields, thus avoiding extensiveexposure to sunlight that could prove damaging or deadly. Because the male albinosremained in the village during the day, they had mating advantages over the males whoparticipated in farming and other duties outside of the village. Albinism was considered tobe a positive trait reflecting the purity of the villagers. Finally, the small population size ofthe Hopi tribe may have helped increase the allele frequency of the albino gene due tochance.2.Outline some of the ways in which genetics is important to all of us.Solution:Genetics directly influences our lives and is fundamental to what and who we are. Forexample, genes affect our appearance (e.g., eye color, height, weight, skin pigmentation,and hair color). Our susceptibility to diseases and disorders is affected by our geneticmakeup. Genetics plays a significant role in researching and developing techniques todiagnose and treat these hereditary diseases. Genes may also influence our intelligence andpersonality. Genetic techniques have enabled scientists to develop genetically modifiedcrops that are resistant to pesticides and herbicides or that have enhanced nutritionalproperties making it possible to produce larger quantities of food for the world’s growingpopulation. Lastly, genetic engineering has made it possible to mass producepharmaceuticals and other substances of commercial value.3.Give at least three examples of the role of genetics in society today.Solution:Genetics plays important roles in the diagnosis and treatment of hereditary diseases: inbreeding plants and animals for improved production and disease resistance; and inproducing pharmaceuticals and novel crops through genetic engineering.4.Briefly explain why genetics is crucial to modern biology.

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2Chapter One: Introduction to GeneticsSolution:Genetics is crucial to modern biology in that it provides unifying principles: The geneticcode is universal, meaning that all organisms use nucleic acid as their genetic material, andall organisms encode genetic information in the same manner. The study of many otherbiological disciplines, such as developmental biology, ecology, and evolutionary biology,is supported by genetics.5.List the three traditional subdisciplines of genetics and summarize what each covers.Solution:1) Transmission (classical) genetics is concerned with the inheritance of genes from onegeneration to the next. It also deals with the location of genes on chromosomes and gene-mapping. 2) Molecular genetics focuses on the structure, organization, and function ofgenes at the molecular level. Molecular genetics is also concerned with the processes bywhich genetic information is transferred and expressed. 3) Population genetics studiesgenetic variation and changes in genes and allele frequencies within groups of individualsof the same species over time.6.What are some characteristics of model genetic organisms that make them useful forgenetic studies?Solution:Model genetic organisms have relatively short generation times, produce numerousprogeny, are amenable to laboratory manipulations, and can be maintained and propagatedinexpensively.Section 1.27.When and where did agriculture first arise? What role did genetics play in the developmentof the first domesticated plants and animals?Solution:Agriculture first arose 10,000 to 12,000 years ago in the area now referred to as the MiddleEast (i.e., Turkey, Iran, Iraq, Syria, Jordan, and Israel). Early farmers selectively bredindividual wild plants or animals that had useful characteristics with others that had similaruseful traits. The farmers then selected for offspring that contained those useful features.Early farmers did not completely understand genetics, but they clearly understood thatbreeding individual plants or animals with desirable traits would lead to offspring thatcontained these same traits. This selective breeding led to the development of domesticatedplants and animals.8.Outline the notion of pangenesis and explain how it differs from the germ-plasm theory.

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Chapter One: Introduction to Genetics3Solution:Pangenesis theorizes that information for creating each part of the offspring’s bodyoriginates from each respective part of the parent’s body and is passed through thereproductive organs to the embryo at conception. Pangenesis suggests that changes in partsof the parent’s body may be passed to the offspring’s body. The germ-plasm theory, incontrast, states that the reproductive cells (eggs and sperm) possess all of the informationrequired to make the complete body; the rest of the body contributes no information to thenext generation.9.What does the concept of the inheritance of acquired characteristics propose and how is itrelated to the notion of pangenesis?Solution:The theory of inheritance of acquired characteristics postulates that traits acquired duringone’s lifetime can be transmitted to offspring. It developed from pangenesis, whichpostulates that information from all parts of one’s body is transmitted to the nextgeneration. Thus, according to the theory of inheritance of acquired characteristics, thedevelopment of large bicep muscles through exercise would produce children with largebiceps.10.What is preformationism? What did it have to say about how traits are inherited?Solution:Preformationism is the theory that the offspring results from a miniature adult that isalready preformed in the sperm or the egg. All traits would thus be inherited from only oneparent, either the father or the mother, depending on whether the homunculus (thepreformed miniature adult) resided in the sperm or the egg.11.Define blending inheritance and contrast it with preformationism.Solution:The theory of blending inheritance proposes that the egg and sperm from two parentscontains material that blends upon conception, influencing the development of theoffspring. This theory indicates that the offspring is an equal blend of the two parents. Inpreformationism, the offspring inherits all of its traits from one parent.12.How did developments in botany in the seventeenth and eighteenth centuries contribute tothe rise of modern genetics?Solution:Botanists of the seventeenth and eighteenth centuries discovered that plants reproducesexually, enabling them to develop new techniques for crossing plants and creating planthybrids. These early experiments provided essential background work for Mendel’s plantcrosses. Mendel’s work laid the foundation for the study of modern genetics.13.List some advances in genetics made in the twentieth century.

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4Chapter One: Introduction to GeneticsSolution:1902Proposal that genes are located on chromosomes by Walter Sutton1910Discovery of the first genetic mutation in a fruit fly by Thomas Hunt Morgan1930The foundation of population genetics by Ronald A. Fisher, John B. S. Haldane,and Sewall Wright1940sThe use of viral and bacterial genetic systems1953Three-dimensional structure of DNA described by Watson and Crick1966Deciphering of the genetic code1973Recombinant DNA experiments1977Chemical and enzymatic methods for DNA sequencing developed byWalter Gilbert and Frederick Sanger1986PCR developed by Kary Mullis1990Gene therapy14.Briefly explain the contribution that each of the following persons made to the study ofgenetics.Solution:a.Matthias Schleiden and Theodor SchwannProposed the concept of the cell theory, which indicated that the cell is the fundamentalunit of living organisms. Caused biologists interested in heredity to examine cellreproduction.b. August WeismannProposed the germ-plasm theory, which holds that cells in reproductive organs carry acomplete set of genetic information.c.Gregor MendelFirst discovered the basic rules of inheritance.d.James Watson and Francis CrickAlong with Rosalind Franklin and Maurice Wilkins, described the three-dimensionalstructure of DNA.e.Kary MullisDeveloped the polymerase chain reaction, used to quickly amplify small amounts of DNA.Section 1.315.What are the two basic cell types (from a structural perspective) and how do they differ?Solution:The two basic cell types are prokaryotic and eukaryotic. Prokaryotic cells have neithermembrane-bound organelles nor a true nucleus. Their chromosomes are found within thecytoplasm. Eukaryotic cells possess a membrane-bound nucleus and other membrane-bound organelles such as an endomembrane system and mitochondria.16.Outline the relations between genes, DNA, and chromosomes.

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Chapter One: Introduction to Genetics5Solution:A gene is a particular DNA nucleotide sequence that encodes an individual trait. Genes arelocated at specific positions on chromosomes.APPLICATION QUESTIONS AND PROBLEMSSection 1.1*17. What is the relation between genetics and evolution?Solution:In essence, evolution is change in the genetic composition of a population over generations.Mutations generate new genetic variants, recombination generates new combinations ofgenetic variants, and natural selection or other evolutionary processes cause a change in theproportions of specific genetic variants in the population.*18. For each of the following genetic topics, indicate whether it focuses on transmissiongenetics, molecular genetics, or population genetics.a.Analysis of pedigrees to determine the probability of someone inheriting a traitSolution:Transmission geneticsb.Study of people on a small island to determine why a genetic form of asthma isprevalent on the islandSolution:Population geneticsc.Effect of nonrandom mating on the distribution of genotypes among a group ofanimalsSolution:Population geneticsd.Examination of the nucleotide sequences found at the ends of chromosomesSolution:Molecular geneticse.Mechanisms that ensure a high degree of accuracy in DNA replication

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6Chapter One: Introduction to GeneticsSolution:Molecular geneticsf.Study of how the inheritance of traits encoded by genes on sex chromosomes (sex-linked traits) differs from the inheritance of traits encoded by genes on nonsexchromosomes (autosomal traits)Solution:Transmission genetics19.Describe some of the ways in which your own genetic makeup affects you as a person. Beas specific as you can.Solution:Answers will vary but should include observations similar to those in the followingexample: Genes affect my physical appearance; for example, they probably have largelydetermined the fact that I have brown hair and brown eyes. Undoubtedly, genes haveaffected my height of five feet, seven inches, which is quite close to the height of my fatherand mother, and my slim build. My dark complexion mirrors the skin color of my mother. Ihave inherited susceptibilities to certain diseases and disorders that tend to run in myfamily; these include asthma, a slight tremor of the hand, and vertigo.20.Describe at least one trait that appears to run in your family (appears in multiple membersof the family). Does this trait run in your family because it is an inherited trait or because itis caused by environmental factors that are common to family members? How might youdistinguish between these possibilities?Solution:Answers will vary but should include observations similar to those in the followingexample: My two brothers and I share two traits: we are all three taciturn (we don’t speakmuch) and smart (just don’t ask my teenage daughter). Although the literature providesevidence for a genetic component for intelligence, I’m not aware of any studies on theheritability of being taciturn. If I were to investigate to what extent these traits aredetermined by the environment or by heredity, I would look at studies of twins who hadbeen separated at birth and lived in different environments to adulthood. Such studieswould separate environmental factors from genetic factors, whereas studies of familymembers reared in the same household are confounded by the fact that the family membersexperienced similar environments. If the trait had a strong genetic component, we wouldexpect identical twins reared apart to be similarly taciturn or similarly intelligent. Onewould have to devise some objective measure of these traits—degrees of being taciturn orsmart.Section 1.2*21. Genetics is said to be both a very old science and a very young science. Explain what ismeant by this statement.

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Chapter One: Introduction to Genetics7Solution:Genetics is old in the sense that humans have been aware of hereditary principles forthousands of years and have applied them since the beginning of agriculture and thedomestication of plants and animals. It is very young in the sense that the fundamentalprinciples were not uncovered until Mendel’s time, and the discovery of the structure ofDNA and the principles of recombinant DNA have occurred within the last 60 years.*22.Match the description (athroughd) with the correct theory or concept listed below.PreformationismPangenesisGerm-plasm theoryInheritance of acquired characteristicsa.Each reproductive cell contains a complete set of genetic information.Solution:Germ-plasm theoryb.All traits are inherited from one parent.Solution:Preformationismc.Genetic information may be altered by use of a characteristic.Solution:Inheritance of acquired characteristicsd.Cells of different tissues contain different genetic information.Solution:Pangenesis*23.Compare and contrast the following ideas about inheritance.a.Pangenesis and germ-plasm theorySolution:Pangenesis theorizes that units of genetic information (pangenes) from all parts of thebody are carried through the reproductive organs to the embryo where each unitdirects the formation of its own specific part of the body. According to the germ-plasm theory, the germ-line tissue or gamete producing cells found within thereproductive organs contain the complete set of genetic information that is passed to

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8Chapter One: Introduction to Geneticsthe gametes. Both theories are similar in that each predicts the passage of geneticinformation occurs through the reproductive organs.b.Preformationism and blending inheritanceSolution:Preformationism predicts that the sperm or egg contains a miniature preformed adultcalled the homunculus. During development, the homunculus would grow to producethe offspring. Only one parent would contribute genetic traits to the offspring.Blending inheritance requires contributions of genetic material from both parents.According to the theory of blending inheritance, genetic contributions from theparents blend to produce the genetic material of the offspring. Once blended, thegenetic material could not be separated for future generations.c.The inheritance of acquired characteristics and our modern theory of hereditySolution:The theory of inheritance of acquired characteristics postulates that traits acquiredduring one’s lifetime alter the genetic material and can be transmitted to offspring.Our modern theory of heredity indicates that offspring inherit genes located onchromosomes from their parents. These chromosomes segregate during meiosis in thegerm cells and are passed into the gametes.Section 1.3*24.Compare and contrast the following terms:a.Eukaryotic and prokaryotic cellsSolution:Both cell types have lipid bilayer membranes, DNA genomes, and machinery forDNA replication, transcription, translation, energy metabolism, response to stimuli,growth, and reproduction. Eukaryotic cells have a nucleus containing chromosomalDNA and possess internal membrane-bound organelles.b.Gene and alleleSolution:A gene is the basic unit of heredity, which is dictated by the nucleotide sequence,and typically encodes a functional RNA or polypeptide. An allele is a variant form ofa gene, arising through mutation.c.Genotype and phenotype

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Chapter One: Introduction to Genetics9Solution:The genotype is the set of genes or alleles an organism has inherited from itsparent(s). The expression of the genes of a particular genotype, through interactionwith environmental factors, produces the phenotype, the observable trait.d.DNA and RNASolution:Both are nucleic acid polymers. RNA contains ribose, whereas DNA containsdeoxyribose. RNA also contains uracil as one of the four bases, whereas DNAcontains thymine. The other three bases are common to both DNA and RNA.Finally, DNA is usually double-stranded, consisting of two complementary strandsand very little secondary structure, whereas RNA is single-stranded with regions ofinternal base-pairing to form complex secondary structures.e.DNA and chromosomeSolution:Chromosomes are structures formed of DNA and associated proteins. Thenucleotide sequence of the DNA contains the genetic information.CHALLENGE QUESTIONS*25.The type of albinism that arises with high frequency among Hopi Native Americans(discussed in the introduction to this chapter) is most likely oculocutaneous albinism typeII, due to a defect in theOCA2gene on chromosome 15. Do some research on the Internetto determine how the phenotype of this type of albinism differs from phenotypes of otherforms of albinism in humans and the mutated genes that result in these phenotypes. Hint:Visit the Online Mendelian Inheritance in Man Web site(http://www.ncbi.nlm.nih.gov/omim/) and search the database for albinism.Solution:Type of albinismPhenotypeGene mutatedOCA2Pigment reduced in skin, hair, and eyes, butsmall amount of pigment acquired with age;visual problemsOCA2OCA1BGeneral absence of pigment in hair, skin, andeyes, but may be small amount of pigment;does not vary with age; visual problemsTyrosinaseOCA1AComplete absence of pigment; visual problemsTyrosinaseOCA3Some pigment present, but sun sensitivity andvisual problemsTyrosinase-relatedprotein 1OASDLack of pigment in the eyes and deafness laterin lifeUnknownOA1Lack of pigment in the eyes but normalelsewhereGPR143 gene, Gprotein-coupled

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10Chapter One: Introduction to GeneticsreceptorROCABright copper red coloration in skin and hair ofAfricans; dilution of color in irisTyrosinase-relatedprotein 1OCA4Reduced pigmentationMATP gene,membrane-associatedtransporterprotein.Section 1.126.We now know a great deal about the genetics of humans, and humans are the focus ofmany genetic studies. Should humans be considered a model genetic organism? Why orwhy not?Solution:Humans are intensively interested in how humans function biologically. Because of thisintense interest, we know more about human anatomy, physiology, genetics, andbiochemistry than we know about many other organisms. Many human diseases anddisorders are associated with human genes. Understanding how to treat and diagnose thesediseases and disorders requires intensive studies to identify the gene(s) responsible for thedisorder as well as understanding how they are inherited and expressed. Recent advancesin the understanding of genetic risk factors associated with diseases such as heart diseaseand cancer have enabled the development of predictive genetic tests for some of thesedisorders. These successes continue to stimulate a focus in identifying genetic risk factorsfor other diseases. The ability of families to keep careful records about membersextending back many generations has facilitated the study of human inheritance aiding theability of researchers to identify genetic markers within families. In addition, these detailedrecords have provided some humans who are intensely interested in their own heredity theability to trace their ancestry.Section 1.3*27.Suppose that life exists elsewhere in the universe. All life must contain some type ofgenetic information, but alien genomes might not consist of nucleic acids and have thesame features as those found in the genomes of life on Earth. What might be the commonfeatures of all genomes, no matter where they exist?Solution:All genomes must have the ability to store complex information, the capacity to vary andyet be transmissible in large part faithfully to subsequent generations. The blueprint for theentire organism must be contained within the genome of each reproductive cell. Theinformation has to be in the form of a code that can be used as a set of instructions forassembling the components of the cells. The genetic material of any organism must bestable, be replicated precisely, and be transmitted faithfully to the progeny, but must becapable of mutating.

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Chapter One: Introduction to Genetics1128.Choose one of the ethical or social issues in partsathrougheand give your opinion on theissue. For background information, you might read one of the articles on ethics markedwith an asterisk in the Suggested Readings section for Chapter 1 athttp://courses.bfwpub.com/pierce5e.a.Should a person’s genetic makeup be used in determining his or her eligibility for lifeinsurance?Solution:Arguments pro:Genetic susceptibility to certain types of diseases or conditions isrelevant information regarding consequences of exposure to certain occupationalhazards. Genes that will result in neurodegenerative diseases, such as Huntingtondisease, Alzheimer disease, or breast cancer, could logically be considered preexistingconditions. Insurance companies have a right, and arguably a duty to their customers,to exclude people with genetic preconditions so that insurance rates can be loweredfor the general population.Arguments con:The whole idea of insurance is to spread the risk and pool assets.Excluding people based on their genetic makeup would deny insurance to people whoneed it most. Indeed, as information about various genetic risks accumulates, morepeople would become excluded until only a small fraction of the population isinsurable. Further, many genes are incompletely penetrant and variably expressed.Not all women who have mutantBRCA1orBRCA2genes develop breast cancer. Andsome women who have breast cancer lack mutations in those genes.b.Should biotechnology companies be able to patent newly sequenced genes?Solution:Pro:Patenting genes provides companies with protection for their investment inresearch and development of new drugs and therapies. Without such patent protection,companies would have less incentive to expend large amounts of money in geneticresearch and thus would slow the pace of advancement of medical research. Such aresult would be detrimental to everyone.Con:Patents on human genes would be like allowing companies to patent a humanarm. Genes are integral parts of our selves, so how can a company patent somethingthat every human has?c.Should gene therapy be used on people?Solution:Pro:Gene therapy can be used to cure previously incurable or intractable geneticdisorders and to relieve the suffering of millions of people.Con:Gene therapy may lead to genetic engineering of people for unsavory ends. Whodetermines what is a genetic defect? Is short stature a genetic defect? Should genetictesting be made available for inherited conditions for which there is no treatment orcure?

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12Chapter One: Introduction to Geneticsd.Should genetic testing be made available for inherited disorders for which there is notreatment or cure?Solution:Pro:Information will provide relief from unnecessary anxiety (if the test is negative).Even if the test result is positive for a genetic disorder, it provides the individual, thefamily, and friends with information and time to prepare. Information about one’sown genetic makeup is a right; every person should be able to make his or her ownchoice as to whether he or she wants this information.Con:If there is no treatment or cure, a positive test result can have no goodconsequences. It’s like receiving a death sentence or sentence of extendedpunishment. It will only engender feelings of hopelessness and depression and maycause some people to terminate their own lives prematurely.29.A 45-year old woman undergoes genetic testing and discovers that she is at high riskfor developing colon cancer and Alzheimer disease. Because her children have 50%of her genes, they also may be at an increased risk for these diseases. Does she have amoral or legal obligation to tell her children and other close relatives about the resultsof her genetic testing?Solution:Legally, she is not required to inform her children or other relatives about her testresults, but people may have different opinions about her moral and parentalresponsibilities. On the one hand, she has the legal right to keep private the results ofany medical information, including the results of genetic testing. On the other hand,her children may be at increased risk of developing these disorders and might benefitfrom that knowledge. For example, the risk of colon cancer can be reduced by regularexams, so that any tumors can be detected and removed before they becomecancerous. Some people might argue that her parental responsibilities includeproviding her children with information about possible medical problems. Anotherissue to consider is the possibility that her children or other relatives might not wantto know their genetic risk, particularly for a disorder like Alzheimer for which there isno cure.30.Suppose that you could undergo genetic testing at age 18 for susceptibility to agenetic disease that would not appear until middle age and has no available treatment.a.What would be some of the possible reasons for having such a genetic test and someof the possible reasons for not having the test?Solution:Having the genetic test removes doubt about the potential for the disorder—either youare susceptible or not. By knowing about the potential of a genetic disorder lifestylechanges could possibly be made to lessen the impact of the disease or lessen the risk.The types and nature of future medical tests could be positively impacted by the

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Chapter One: Introduction to Genetics13genetic testing, thus allowing for early warning and screening for the disease. Theknowledge could also have impact on future family plans and allow for informeddecisions regarding future offspring and the potential of passing the trait to youroffspring. Also by knowing the future, one could plan one’s life accordingly.Reasons for not having the test typically revolve around the potential for testingpositive for the susceptibility to the genetic disease. If the susceptibility was detected,the potential for discrimination could exist. For example, your employer (or possiblyfuture employer) might see you as a long-term liability, thus affecting employmentoptions. Insurance companies may not want to insure you for that condition orsymptoms of the disorder, and potentially social stigmatism associated with thedisease could be a factor. Knowledge of the potential future condition could lead topsychological difficulties in coping with the anxiety of waiting for the disease tomanifest.b.Would you personally want to be tested? Explain your reasoning.Solution:There is no “correct” answer, but for me, yes, I would personally want to be tested.The test would remove doubt about the susceptibility particularly if the geneticdisease had been demonstrated to occur in my family. Either a positive or negativeresult would allow for informed planning of lifestyle, medical testing, and familychoices in the future.

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Chapter Two: Chromosomes and Cellular ReproductionCOMPREHENSION QUESTIONSSection 2.11.What are some genetic differences between prokaryotic and eukaryotic cells?Solution:Prokaryotic cellEukaryotic cellNo nucleusNo paired chromosomes (haploid)Typically single circular chromosomecontaining a single origin of replicationSingle chromosome is replicated with eachcopy moving to opposite sides of the cellNo histone proteins bound to DNANucleus presentPaired chromosomes common (diploid)Typically multiple linear chromosomescontaining centromeres, telomeres, andmultiple origins of replicationChromosomes are replicated and segregateduring mitosis or meiosis to the properlocationHistone proteins are bound to DNA2.Why are the viruses that infect mammalian cells useful for studying the genetics ofmammals?Solution:It is thought that viruses must have evolved after their host cells because a host isrequired for viral reproduction. Viral genomes are closely related to their host genomes.The close relationship between a mammalian virus and its mammalian cell host, alongwith the simpler structure of the viral particle, makes it useful in studying the genetics ofmammals. The viral genome will have a similar structure to the mammalian cell host,but because it has fewer genes, it will be easier to decipher the interactions andregulation of the viral genes.Section 2.23.List three fundamental events that must take place in cell reproduction.Solution:(1)A cell’s genetic information must be copied.(2)The copies of the genetic information must be separated from one another.(3)The cell must divide into two daughter cells.4.Outline the process by which prokaryotic cells reproduce.

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Chapter Two: Chromosomes and Cellular Reproduction15Solution:(1)Replication of the circular chromosome takes place.(2)The two replicated chromosomal copies attach to the plasma membrane.(3)The plasma membrane grows, which results in the separation of the twochromosomes.(4)A new cell wall is formed between the two chromosomes, producing two cells, eachwith its own chromosome.5.Name three essential structural elements of a functional eukaryotic chromosome anddescribe their functions.Solution:(1)Centromere: serves as the point of attachment for the kinetochore to which spindlefibers (microtubules) attach(2)Telomeres, or the natural ends of the linear eukaryotic chromosome: serve tostabilize the ends of the chromosome; may have a role in limiting cell division(3)Origins of replication: serve as the starting place for DNA synthesis6.Sketch and identify four different types of chromosomes based on the position of thecentromere.Solution:metacentricsubmetacentricacrocentrictelocentric7.List the stages of interphase and the major events that take place in each stage.Solution:Three predominant stages are found in interphase of cells active in the cell cycle.(1)G1(Gap1):In this phase, the cell grows and synthesizes proteins necessary for celldivision. During G1, the G1/S checkpoint takes place. Once the cell has passed thischeckpoint, it is committed to divide.(2)S phase: During S phase, DNA replication takes place.(3)G2(Gap2): In G2, additional biochemical reactions take place that prepare the cellfor mitosis. A major checkpoint in G2is the G2/M checkpoint. Once the cell haspassed this checkpoint, it enters into mitosis.A fourth stage is frequently found in cells prior to the G1/S checkpoint. Cells may exitthe active cell cycle and enter into a nondividing stage called G0.8. What are checkpoints? List some of the important checkpoints in the cell cycle.

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