Name ___________________________________ Class _____ Date ____________________AP Biology – Unit 3 Active Reading Guide

Unit 3.1: The Cell Cycle & Mitosis

1. Give an example of the three key roles of cell division.Key Role ExampleReproductionGrowth and DevelopmentTissue Renewal

2. What is meant by the cell cycle?

3. What is the meaning of genome?

4. How many chromosomes are in a human somatic cell? __________5. Name two types of somatic cells in your body.

6. What is a gamete?

7. Name the two types of gametes. _______________ and _______________8. How many chromosomes in a human gamete? __________9. Define chromatin.

10.Think carefully, now. How many DNA molecules are in each of your somatic cells?

11.You are going to have to learn the difference between several similar-sounding terms. Slide 13 represents a replicated chromosome that has two sister chromatids. The narrow “waist” represents the location of the centromere. Students often get all these terms confused, so take time now to draw a quick sketch of a chromosome and label the following areas: chromosome, chromatid, centromere, chromatin.

12.Study slide 15 in the lecture. Summarize what occurs at the DNA level in each stage.

13.What is mitosis? How is it different from cytokinesis?

14.What occurs in meiosis? How is the chromosome number of daughter cells different?

15.Select either mitosis or meiosis to answer the following questions.a. ______________ By what process are the damaged cells in a wound b. ______________ By what process are eggs formed?c. ______________ By what process does a zygote develop into a multicellular d. ______________ In which process are identical daughter cells produced?e. ______________ Which process reduces chromosome number of daughter

16.A hedgehog has 90 chromosomes in its somatic cells.a. How many chromosomes did the hedgehog inherit from each parent _____b. How many chromosomes are in each of the hedgehog’s gametes? _____c. How many chromosomes will be in each somatic cell of the hedgehog’s offspring

_____17.Give a brief explanation of what happens in each phase of the cell cycle listed.

Phase

Explanation

G1

S

G2

M

18.What are the components of the mitotic spindle? What is the source of these components?

19.In animal cells, the assembly of spindle microtubules starts at the centrosome. What is another name for the centrosome?

20.Sketch and label a centrosome with two centrioles.

21.What are the components of the mitotic spindle?

22.Describe what happens to the centrosome during interphase and then prophase.

23.What is a kinetochore? Read your text carefully, and then make a labeled sketch that shows a replicated chromosome with two kinetochores and some attached spindle fibers. Slide 36 in the lecture may help.

24.Explain the difference between kinetochore and nonkinetechore microtubules. What is the function of each?

25.At which end do kinetochore microtubules shorten during anaphase? Explain the Inquiry Figure (slide 38) that supports where this shortening occurs.

26.Describe cytokinesis in an animal cell. Use a labeled sketch that shows the cleavage furrow.

27.Describe cytokinesis in a plant cell. Use a labeled sketch that shows the cell plate.

28.How is the cell plate formed? What is the source of the material for the cell plate?

29.Prokaryote reproduction does not involve mitosis, but instead occurs by binary fission. This process involves an origin of replication. Describe binary fission.

30.Notice that now you are learning a number of differences between prokaryotic and eukaryotic cells. Besides the fact that prokaryotes lack a membrane-bounded nucleus, describe the following differences:

a. Mode of reproduction?

b. Number of chromosomes?

c. Shape of the bacterial chromosome?

31.What controls the cell cycle? Study the Inquiry on slide 48 in the lecture to help you answer this question.

32.What is a cell cycle checkpoint?

33.Summarize what happens at each checkpoint. You may add to this chart as you study this section.Checkpoint

What Happens How is it controlled?

G1

S

G2

M

34.What is the G0 phase? Describe this phase.

35.What is a protein kinase?

36.Kinases drive the cell cycle, but they must be activated by attachment of a _______________.

37.The activity of cyclin-dependent kinases (CDks) rises and falls. Why?

38.What does MPF trigger? What are some specific activities that it triggers?

39.What happens if all the chromosome kinetochores are not attached to spindle fibers? When this occurs, which checkpoint is not passed?

40.What are growth factors? How does platelet–derived growth factor (PDGF) stimulate fibroblast division?

41.Cancer cells exhibit different behaviors than normal cells. Here are two normal behaviors they no longer show. Explain each behavior. density-dependent inhibition: anchorage dependence:

42.Cancer cells also show loss of cell cycle controls and may divide without being checked. The story of HeLa cells is worth noting. What is their source? How old are they? Note that, unlike normal cells, HeLa cells are immortal!

43.What is transformation? What is metastasis?

44.Distinguish between a benign tumor and a malignant tumor.

45.List two specific cancer treatments, and tell how each treatment works.

Unit 3.2: Meiosis and Sexual Life Cycles

1. Let’s begin with a review of several terms that you may already know. Define:a. Gene: b. Locus: c. Gamete: d. Male gamete: e. Female gamete: f. Asexual reproduction: g. Sexual reproduction:

2. How many chromosomes are in human cells? What is a chromosome?

3. Which type of reproduction will result in genetically identical offspring?

4. What is a somatic cell? Give examples of two human somatic cell types.

5. How does a somatic cell compare to a gamete in terms of chromosome number?

6. What is a karyotype? How is it prepared?

7. What are three things that can be determined from a karyotype? (Study the Research Method, slide 10, in the lecture carefully for this information.)

8. Explain what is meant by homologous chromosomes.

9. Cells that have only one of each homologous pair are said to be haploid, a condition that is represented by n. Cells that have two of each homologous pair are said to be diploid or 2n. For each of the following, is the cell haploid or diploid?

a. liver cell ____________________ e. skin cell ____________________b. gamete ____________________ f. sperm ____________________c. egg cell ____________________ g. somatic cell __________________d. zygote ____________________ h. sex cell ____________________

10.The muscle cells of a dog have 78 chromosomes. Fill in the correct chromosome number in a

a. bone cell _____ b. sperm _____ c. haploid cell _____d. somatic cell _____ e. zygote _____

11.In Slide 14, the chromosomes are shaded in two colors to represent the parent of origin.

a. How many chromosomes does the cell above have? _____b. How many homologous pairs? _____c. How many chromatids? _____d. Is this cell haploid or diploid? __________

12.Where are the gametes of an animal produced? Be specific as to male and female gametes.

13.By what process are gametes produced? _____________________14.What is another term for a fertilized egg? _______________

a. What is the chromosome number of the fertilized egg? (Answer this in general terms, haploid, n, or diploid, 2n). _________________________

15.What is the purpose of meiosis?

16.Study slides 19, 22, and 24 in the lecture. You will see that plants have a life cycle that involves spores, which form as a result of meiosis, so these spores are haploid. Notice also that both haploid and diploid cells can divide by mitosis. However, meiosis always begins with cells that are __________, and as a result of meiosis, daughter cells are formed that are always __________. These cells can be gametes (in animals) or spores (in plants).

17.Your study of plants this year will include knowing that they exhibit alternation of generations.

a. What does this mean?b. What are the two generations?c. Which is haploid, and which is diploid?

18.What are alleles? Give an example.

19.In meiosis, the DNA is replicated during interphase, followed by two divisions. The first division is meiosis I. Study the events of prophase I as they are significant. Explain each of these events:

synapsis:crossing over:chiasmata:

20.How is the arrangement of chromosomes different from metaphase of mitosis?

21.There are 2 divisions in meiosis. What will separate in the first division in meiosis I?

22.Now study the chromosomes in anaphase I and telophase I carefully.a. How many chromosomes are in each cell at the end of the first meiotic division?

_________b. Are the resultant daughter cells haploid, or diploid? __________

23.During meiosis I, homologous chromosomes separate. What separates during meiosis II?

24.To check that you have the big picture, here are some quick review questions.a. What happens to the chromosome number in meiosis?b. During which division is the chromosome number reduced?c. What is the purpose of meiosis?d. How many times does the cell divide in meiosis?e. How many times do the chromosomes duplicate?f. How many daughter cells are formed?g. What is the chromosome number?h. What are homologs (homologous chromosomes)?

i. What occurs in synapsis?j. What is crossing over?

25.Students often get confused about the differences between mitosis and meiosis. To help with this, work through the following chart:

Mitosis MeiosisRole in animal bodyNumber of DNA replicationsNumber of DivisionsNumber of Daughter CellsChromosome # in daughter cells26.Synapsis and crossing over are unique to meiosis. During what specific phase do these

occur?

27.Explain the physical events of crossing over. You may wish to make a sketch of the event. Include these terms: synaptonemal complex, chiasmata, homologs, sister chromatids.

28.An important idea for you to understand is that new alleles arise by changes in the DNA or mutation, but genetic diversity occurs when the deck that is dealt is simply reshuffled. So, there are three ways that sexually reproducing organisms “shuffle the deck.” They are listed below. Explain what occurs in each, and how this increases diversity.

a. independent assortment of chromosomes:

b. crossing over:

c. random fertilization:

29.Here is a fun exercise to drive this point home. Pull out your calculator, and try your hand at this. When you were conceived, what were the odds that of the many possibilities, your parents would come up with you?

a. The number of different gametes that can be formed because of independent assortment is 2n, where n = the number of homologous pairs. Therefore, since humans have 46 chromosomes or 23 homologous pairs, what is the number of possible gametes that can be formed due to independent assortment of chromosomes?

b. Now, this is the number of unique gametes your mom could have made. Your father could have made the same number. To see the effect of random fertilization, multiply the number of gametes one parent could make by the number of unique gametes the other parent could make.

Your answer should be in the trillions, and all of this is without crossing over. See how special you are?

Unit 3.3: Mendelian Patterns of InheritanceIf you have completed a first-year high school biology course, some of this chapter will serve as a review for the basic concepts of Mendelian genetics. For others, this may be your first exposure to genetics. In either case, this is a chapter that should be carefully mastered. Spending time with this chapter, especially working genetics problems, will give you a solid foundation for the genetics units in the chapters to come.

1. One of the keys to success for Mendel was his selection of pea plants. Explain how using pea plants allowed Mendel to control mating; that is, how did this approach let Mendel be positive about the exact characteristics of each parent?

2. What is the difference between a character and a trait? Explain using an example.

3. Define the following terms. Then, consider your own family. Which generation would your mother’s grandparents be? Your mother? You?

a. P generation:b. F1 generation:c. F2 generation:

4. Explain how Mendel’s simple cross of purple and white flowers did the following:a. refuted blending:b. determined dominant and recessive characteristics:c. demonstrated the merit of experiments that covered multiple generations:

5. In sexually reproducing organisms, why are there exactly two chromosomes in each homologous pair?

6. Mendel’s model consists of four concepts. Describe each concept in the appropriate space below. Indicate which of the concepts can be observed during meiosis by placing an asterisk by the concept.

Mendel’s Four Concepts

Description of Concept

First Concept

Second Concept

Third ConceptFourth Concept(Law of Segregation)

7. Using slide 18 in the lecture as your guide, indicate the alleles for each individual as well as the gametes it produces, and complete the Punnett square.

a. What is the F2 phenotypic and genotypic ratio?b. Which generation is completely heterozygous?c. Which generation has both heterozygous and homozygous offspring?

8. In pea plants, T is the allele for tall plants, while t is the allele for dwarf plants. If you have a tall plant, demonstrate with a testcross how it could be determined if the plant is homozygous tall or heterozygous tall.

9. Explain the difference between a monohybrid cross and a dihybrid cross.

10.As you start to work word problems in genetics, two things are critical: the parent’s genotype must be correct, and the gametes must be formed correctly. Using slide 27 as your guide, explain how the gametes are derived for the following cross. (You should have four different gametes).

YyRr X YyRr

11.Complete the cross given in question 10 by placing the gametes in a Punnett square. Then provide the phenotypic ratio of the offspring.

12.Explain Mendel’s law of independent assortment.

13.An event that is certain to occur has a probability of _____, while an event that is certain not to occur has a probability of _____.

14.In probability, what is an independent event?

15.State the multiplication rule and give an original example.

16.State the addition rule and give an original example.

17.What is the probability that a couple will have a girl, a boy, a girl, and a boy in this specific order? Show your work!

18.Explain how incomplete dominance is different from complete dominance, and give an example of incomplete dominance.

19.Compare and contrast codominance with incomplete dominance.

20.Dominant alleles are not necessarily more common than recessive alleles in the gene pool. Explain why this is true.

21.Explain what is meant when a gene is said to have multiple alleles. Blood groups are an excellent human example of this.

22.Blood groups are so important medically that you should be able to solve genetics problems based on blood types. The first step in accomplishing that is to understand the genotypes of each blood type. Before working any problems, complete this ABO blood type chart.

Phenotype(blood type)

Genotype(s) Red Blood Cell Appearance

A

B

AB

O

23.What is pleiotropy? Explain why this is important in diseases like cystic fibrosis and sickle-cell disease.

24.Explain epistasis.

25.Explain why the dihybrid cross detailed in slide 50 in the lecture has four yellow Labrador retrievers instead of the three that would have been predicted by Mendel’s work.

26.Why is height a good example of polygenic inheritance?

27.Quantitative variation usually indicates ______________________________.

28.Using the terms norm of reaction and multifactorial, explain the potential influence of the environment on phenotypic expression.

29.Pedigree analysis is often used to determine the mode of inheritance (dominant or recessive, for example). Be sure to read the “Tips for pedigree analysis” in slide 56 in the lecture; then complete the unlabeled pedigree by indicating the genotypes for all involved.

a. Is a widow’s peak a dominant or recessive trait?b. Is an attached earlobe a dominant or recessive trait?

30.Describe what you think is medically important to know about the behavior of recessive alleles.

31.You are expected to have a general knowledge of the pattern of inheritance and the common symptoms of a number of genetic disorders. Provide this information for the disorders listed below.

a. cystic fibrosis:b. sickle-cell disease:c. achondroplasia:d. Huntington’s disease:

32.What is the chromosome theory of inheritance?

33.Explain the law of segregation. Use two different colored pencils to illustrate the segregation of alleles. You may want to consult Slide 73 in the lecture, and model your sketches on this.

34.Explain the law of independent assortment. To demonstrate that you understand this concept, consider a cell with two pairs of chromosomes. Sketch the two different ways these chromosomes might be arranged during metaphase I.

35.Thomas Hunt Morgan selected Drosophila melanogaster as his experimental organism. List at least three reasons the fruit fly is an excellent subject for genetic studies.

36.The notation for wild type and mutant traits follows some accepted conventions. Notate the following genotypes for a female fruit fly:

a. a fly homozygous for red eyes _______________b. a fly heterozygous for red eyes _______________c. a fly homozygous for white eyes _______________

37.When Thomas Hunt Morgan mated a white-eyed male fly with a red-eyed female, he came to the startling conclusion that the trait for eye color was located on the chromosome that determines sex. Show this cross. Begin with the parental generation, and go through the F2.

a. Parental generation:b. F1 generation:c. F2 generation:

38.What unusual result suggested that the eye-color trait is located on the X chromosome?

39.What is the SRY gene? Where is it found, and what does it do?

40.What is the definition of a sex-linked gene?

41.In humans, how has that term been historically modified?

42.Name and describe three human sex-linked disorders.

43.Try the following problem (slide 93 - b). A female who carries an allele for color blindness, but who is not color-blind, mates with a male who has normal color vision. What is the probability that they will have a son who is color-blind? Show your work!

44.What is a Barr body? Why do human females show a Barr body in their cells?

45.X inactivation maintains the proper gene dosage. How is the X chromosome inactivated?

46.Why can you say that all calico cats are females?47.What are linked genes? Do linked genes sort independently?

48.If two genes are linked on the same chromosome, we call this combination the parental combination. These genes will be transmitted as a unit and will not sort independently.

However, during meiosis, crossing over occurs between homologous chromosomes, and the linked genes can become “unlinked.” In general, the farther two genes are from each other along the chromosome, the more often they will come “unlinked.” Genetic recombination is the process during which linked genes become unlinked. What do geneticists call the offspring that show these new combinations?

49.Review meiosis. When does crossing over occur?

50.Alfred H. Sturtevant, a student of Thomas Hunt Morgan, used assumptions from observations of crossovers to map genes. What is a linkage map?

51.What is a map unit?

52.Slides 108-111 shows the results of a cross between a fruit fly that is heterozygous for a gray body with normal wings, and a fruit fly that has a black body with vestigial wings. Because these genes are linked, the results are not what might have been predicted. Show the phenotypes and number of each type of offspring. Indicate which offspring are the recombinants and which are the parental type. Finally, calculate the map distance between the two genes. Show all your work here.

53.What occurs in nondisjunction?

54.Explain each of the following terms:a. aneuploidy:b. monosomy:c. trisomy:d. polyploidy:

55.What causes Down syndrome? What are four characteristics of Down syndrome?

56.For each of the following human aneuploidies, give the sex of the individual as well as any physical manifestation of the syndrome.

Sex Physical TraitsXXY

XXX

XO

XYY

57.Chromosome structure can be altered in several ways. Explain what occurs in each type of alteration.

a. deletion:

b. duplication:

c. inversion:

d. translocation:

Unit 3.4: Molecular Biology of the Gene

1. What are the two chemical components of chromosomes?

2. Why did researchers originally think that protein was the genetic material?

3. Distinguish between the virulent and nonvirulent strains of Streptococcus pneumoniae studied by Frederick Griffith.

4. What was the purpose of Griffith’s studies?

5. Summarize the experiment in which Griffith became aware that hereditary information could be transmitted between two organisms in an unusual manner.

6. Define transformation.

7. What did Oswald Avery determine to be the transforming factor? ______________ Explain his experimental approach.

8. Sketch a T2 bacteriophage and label its head, tail sheath, tail fiber, and DNA.

9. How did Hershey and Chase “label” viral DNA and viral protein so that they could be distinguished? Explain why they chose each radioactive tag in light of the chemical composition of DNA and protein.

10.Describe the means by which Hershey and Chase established that only the DNA of a phage enters an E. coli cell. What conclusions did these scientists draw based on these observations?

11.What are Chargaff’s rules? How did he arrive at them?

12.List the three components of a nucleotide.

13.Who are the two men who built the first molecular model of DNA and shared the 1962 Nobel Prize for discovery of its structure?

14.What was the role of Rosalind Franklin in the discovery of the double helix?

15.Distinguish between the structure of pyrimidines and purines. Explain why adenine bonds only to thymine.

16.How did Watson and Crick’s model explain the basis for Chargaff’s rules?

17.Given that the DNA of a certain fly species consists of 27.3% adenine and 22.5% guanine, use Chargaff’s rules to deduce the percentages of thymine and cytosine.

18.Name the five nitrogenous bases, and put a checkmark in the correct column for each base. Also indicate if the base is found in DNA, RNA, or both.Nitrogenous Base Purine Pyrimidine DNA, RNA, or Both

19.What DNA base is complementary to adenine? _________________________ What DNA base is complementary to guanine? _________________________

20.Describe the structure of DNA relative to each of the following:a. distance across molecule ___________b. distance between nucleotides ___________c. distance between turns ___________d. components of the backbone ___________e. components of the “rungs” ___________

21.Explain what is meant by 5' and 3' ends of the nucleotide.

22.What do we mean when we say the two strands of DNA are antiparallel?

23.What is the semiconservative model of replication?

24.Who performed the experiments that elucidated the correct mechanism of DNA replication?

25.How did Meselson and Stahl create “heavy” DNA for their experiments?

26.Use slides 30-32 to explain how Meselson and Stahl confirmed the semiconservative mechanism of DNA replication.

27.Define the origins of replication.

28.Distinguish between the leading and the lagging strands during DNA replication.

29.What is the direction of synthesis of the new strand? ________________________30.What are Okazaki fragments? How are they welded together?

31.Which enzyme does each of the following?a. untwists and separates strands ______________________________________b. holds DNA strands apart ___________________________________________c. synthesizes RNA primer ___________________________________________d. adds DNA nucleotides to new strands _________________________________e. relieves strain caused by unwinding __________________________________f. joins DNA fragments together _______________________________________g. removes RNA primer and replaces with DNA ___________________________

32.Make a detailed list of the steps that occur in the synthesis of a new strand.

33.What is a thymine dimer? How might it occur? How is it repaired?

34.Make a sketch of a chromosome and label the telomeres.

35.Explain telomere erosion and the role of telomerase.

36.Why are cancer cells immortal even though most body cells have a limited life span?

37.Explain the roles of each of the following enzymes in DNA proofreading and repair.a. DNA polymerase _________________________________________________b. Nuclease _______________________________________________________c. Ligase _________________________________________________________d. Repair enzymes __________________________________________________

38.On the following diagram, identify the following: 30-nm fiber, metaphase chromosome, double helix, histone proteins, nucleosomes, protein scaffold, and looped domains (300-nm fiber).

39.Distinguish between heterochromatin and euchromatin.

Unit 3.5: From Gene to ProteinThis is going to be a very long journey, but it is crucial to your understanding of biology. Work on this chapter a single concept at a time, and expect to spend at least 6 hours to truly master the material. Good luck, and take your time.

1. What is gene expression?

2. What situation did Archibald Garrod suggest caused “inborn errors of metabolism”?

3. Describe one example Garrod used to illustrate his hypothesis.

4. State the hypothesis formulated by George Beadle while studying eye color mutations in Drosophila.

5. What strategy did Beadle and Tatum adopt to test this hypothesis?

6. Which organism did Beadle and Tatum use in their research? ________________. How did this organism’s nutritional requirements facilitate this research?

7. How were Neurospora spores treated to increase the mutation rate?

8. Cite two significant findings that resulted from the research of Beadle and Tatum.

9. What revision of detail (but not of basic principle) did this hypothesis undergo as more information was gained? Write this restatement and then highlight it. This is an important concept!

Basic Principles of Transcription and TranslationThis section will introduce you to the processes and associated terminology in the form of an overview. Once you have the big picture, you will take a closer look in the next few concepts.

10.From the first paragraph in this section, find three ways in which RNA differs from DNA.1. ________________________________________________________________

2. ________________________________________________________________

3. ________________________________________________________________

11.What are the monomers of DNA and RNA? ________________________________Of proteins? ______________________________

12.Define each of these processes that are essential to the formation of a protein:transcription:

translation:

13.Complete the following table to summarize each process.Template Product Synthesized Location in the Eukaryotic

CellTranscription

Translation

14.In eukaryotes, what is the pre-mRNA called? _________________________15.Write the central dogma of molecular genetics, as proclaimed by Francis Crick, in the

box below.

16.How many nucleotide bases are there? _______ How many amino acids? _______17.How many nucleotides are required to code for these 20 amino acids? _______18.So, the language of DNA is a triplet code. How many unique triplets exist? _______19.DNA is double-stranded, but for each protein, only one of these two strands is used to

produce an mRNA transcript. What is the coding strand called? _____________20.Here is a short DNA template. Below it, assemble the complementary mRNA strand.

3' A C G A C C A G T A A A 5'

21.How many codons are there above? _____ Label one codon.22.Describe Nirenberg’s experiment in which he identified the first codon.

23.What was the first codon–amino acid pair to be identified? ____________________24.Of the 64 possible codons, how many code for amino acids? _______25.What event is coded for by UAA, UAG, and UGA? _______26.What is the start codon? ________27.Why is the genetic code said to be redundant but not ambiguous?

28.Explain the concept of reading frame.

29.Now here is an important idea: DNA is DNA is DNA. By this we mean that the code is nearly universal, and because of this, jellyfish genes can be inserted into pigs, or firefly genes can make a tobacco plant glow. Enjoy a look at slide 23 in your text... and no question to answer here!

30.Name the enzyme that uses the DNA template strand to transcribe a new mRNA strand.

31.Recall from Chapter 13 that DNA polymerase III adds new nucleotides to the template DNA strand to assemble each new strand of DNA. Both enzymes can assemble a new polynucleotide only in the 5’ direction. Which enzyme, DNA polymerase III or RNA polymerase, does not require a primer to begin synthesis?

32.What is a transcription unit?

33.Slide 26 in the lecture will require a bit of study. Name the three stages of transcription and briefly describe each stage.1._______________________ ________________________________________________________________2. _______________________________________________________________________________________3.

_______________________________________________________________________________________34.Let’s now take a closer look at initiation. Read the paragraph titled “RNA Polymerase

Binding and Initiation of Transcription” carefully. List three important facts about the promoter here.1._______________________ ________________________________________________________________2. _______________________________________________________________________________________3. _______________________________________________________________________________________

35.Use slide 31 in your text to explain the three stages of initiation.1._______________________ ________________________________________________________________2. _______________________________________________________________________________________3. _______________________________________________________________________________________

36.What is the TATA box? How do you think it got this name?

37.What comprises a transcription initiation complex?

38.Now it is time to put all of the elements of transcription together. Write a short essay below to describe the process by which mRNA is formed. Use these terms correctly in your essay, and highlight (or underline) each one: TATA box, gene, terminator, promoter, elongation, 5' to 3', termination, initiation RNA, polymerase RNA nucleotides, template, start point, termination signal, and transcription factors.

39.RNA processing occurs only in eukaryotic cells. The primary transcript is altered at both ends, and sections in the middle are removed.

a. What happens at the 5' end?

b. What happens at the 3' end?

40.What are three important functions of the 5' cap and poly-A tail?1._______________________ ________________________________________________________________2. _______________________________________________________________________________________3. _______________________________________________________________________________________

41.Distinguish between introns and exons. Perhaps it will help to remember this: Exons are expressed.

42.What are snRNPs? What two types of molecules make up a snRNP?

43.You will be introduced to a number of small RNAs in this course. What type is the RNA in a snRNP?

44.SnRNPs band together in little groups to form spliceosomes. How do spliceosomes work?

45.Study the figure and text carefully to explain how the splice sites are recognized.

46.What is a ribozyme?

47.What commonly held idea was rendered obsolete by the discovery of ribozymes?

48.What are three properties of RNA that allow it to function as an enzyme?1._______________________ ________________________________________________________________2. _______________________________________________________________________________________3. _______________________________________________________________________________________

49.What is the consequence of alternative splicing of identical mRNA transcripts?

50.Three types of RNA are needed for protein synthesis. Complete the chart below.Type of RNA Description FunctionmRNA

tRNA

rRNA

51.What is an anticodon?

52.Transfer RNA has two attachment sites. What binds at each site? Sketch tRNA to indicate the two attachment sites, and note where complementary base pairing and hydrogen bonding occur to give it shape.

53.How many different aminoacyl-tRNA synthetases are there? _____54.Scientists expected to find one aminoacyl-tRNA synthetase per codon, but far fewer

have been discovered. How does wobble explain this?

55.Explain the process of a specific amino acid being joined to a tRNA. Be sure to use the words aminoacyl-tRNA synthetase, ATP, amino acid, and tRNA.

56.Describe the structure of a eukaryotic ribosome.

57.How does a prokaryotic ribosome differ from a eukaryotic ribosome? What is the medical significance of this difference?

58.Explain the functions of the A, P, and E sites on a ribosome.

59.Much like transcription, we can divide translation into three stages. List them.

60.Summarize the events of initiation. Include these components: small ribosomal subunit, large ribosomal subunit, mRNA, initiator codon, tRNA, Met, initiation complex, P site, and GTP.

61.What is always the first amino acid in the new polypeptide? ___________________62.Now, summarize the events of elongation. Include these components: mRNA, A site,

tRNA, codon, anticodon, ribozyme, P site, and E site.

63.What is a release factor? By what mechanism is termination accomplished?

64.What is a polyribosome?

65.What are some of the things that will result in a final-form functional protein?

66.Describe at least three types of post-translational modifications.

67.Explain how proteins are targeted for the ER.

68.Define a mutation in terms of molecular genetics.

69.Define point mutations.

70.What are frameshift mutations? Identify two mechanisms by which frameshifts may occur.

71.What is the difference between a nonsense and missense mutation?

72.How can a nucleotide-pair substitution result in a silent mutation?

73.What are the two categories of mutagens?

74.Describe the action of different types of chemical mutagens.

75.Describe two important ways in which bacterial and eukaryotic gene expression differ.

76.What is a gene? It used to be simply stated that one gene codes for one polypeptide. That definition has now been modified. Write below the broader molecular definition in use today.

Unit 3.6: Regulation of Gene ExpressionThe overview for this part of Unit 3.5 introduces the idea that while all cells of an organism have all genes in the genome, not all genes are expressed in every cell. What regulates gene expression? Gene expression in prokaryotic cells differs from that in eukaryotic cells. How do disruptions in gene regulation lead to cancer? This chapter gives you a look at how genes are expressed and modulated.

1. All genes are not “on” all the time. Using the metabolic needs of E. coli, explain why not.

2. What are the two main ways of controlling metabolism in bacterial cells?

3. Feedback inhibition is a recurring mechanism throughout biological systems. In the case of E. coli regulating tryptophan synthesis, is it positive or negative inhibition? Explain your choice.

4. What is a promoter?

5. What is the operator? What does it do?

6. What is an operon?

7. List the three components of an operon, and explain the role of each one.

8. How does a repressor protein work?

9. What are regulatory genes?

10.Distinguish between inducible and repressible operons, and describe one example of each type.

11.Draw a sketch of the lac operon with the following terms: operon genes, operon, RNA polymerase, mRNA, repressor protein, operator, repressor, regulatory gene, inducer. Know the function of each structure.

12.Compare and contrast the lac operon and the trp operon.

13.What happens when a repressor is bound to the operator?

14.What is CAP? How does CAP work?

15.Explain why CAP binding and stimulation of gene expression is positive regulation.

16.Describe the relationship between glucose supply, cAMP, and CAP.

17.How can both repressible and inducible operons be negative regulators?

18.Even though all cells of an organism have the same genes, there is differential gene expression. What does this mean?

19.What percentage of the genes of a typical human cell is expressed at any given time?

20.What is the common control point of gene expression for all organisms?

21.Gene expression can be regulated by modifications of the chromatin. Distinguish between heterochromatin and euchromatin as to their structure and activity.

22.What occurs in histone acetylation? How does it affect gene expression?

23.What is DNA methylation? What role may it play in gene expression?

24.The inactive mammalian X chromosome is heavily methylated. What is the result of this methylation?

25.What is genomic imprinting, and how is it maintained? Give an example discussed earlier in human genetics.

26.Explain what is meant by epigenetic inheritance, and give an example of epigenetic changes discussed in the text or in class.

27.Explain how enhancers and activators interact with transcription factors to affect gene expression.

28.In prokaryotes, functionally related genes are usually clustered in a single operon. What has been found to be the case in eukaryotes?

29.Operons have not been found in eukaryotic cells, and the genes coding for the enzymes of a particular metabolic pathway are often scattered over different chromosomes. What is a plausible mechanism for the coordination of gene expression?

30.How can alternative RNA splicing result in different proteins derived from the same initial RNA transcript?

31.Posttranscriptional control includes regulation of mRNA degradation. Explain how this affects translation.

32.How can proteins be activated, processed, and degraded? Give an example or describe each process.

33.It is now known that much of the RNA that is transcribed is not translated into protein. These RNAs are called noncoding RNAs. Read carefully to discern a crucial role played by these RNAs. What is this role?